miniDSP C-DSP 8x12 DL Processor – Review and Setup/Tuning Guide

Manufacturer & Model
miniDSP C-DSP 8x12 DL
MSRP
$940 (with UMIK-1) $890 (without UMIK-1)
Link
https://www.minidsp.com/products/car-audio-dsp/cdsp-8x12-dl
Highlights
Dirac Live correction in a car-audio DSP, 8 inputs for active systems, Flexible routing, mixer, and bass management, PEQ, delay, crossovers, and all-pass filters, Strong measured performance for the price.
Summary
The miniDSP C-DSP 8x12 DL is not the easiest DSP to configure, but it remains one of my favorite processors because of Dirac Live. With proper setup, careful measurements, and realistic target curves, it can provide the brains for a clean, controlled, and highly enjoyable vehicle audio system.
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Index

Introduction
The miniDSP C-DSP 8x12 DL is one of the most powerful and flexible processors available for modern car-audio systems, offering a feature set that rivals… and in some cases exceeds… more expensive alternatives. With eight input channels, extensive routing and mixing capabilities, per-channel PEQ, delays, all-pass filters, and integration with Dirac Live, the unit can handle highly complex, fully active multi-way systems with precision. It has earned consistent praise from experienced users for its transparency, stability, and configurability, particularly among those willing to invest the time to understand its capabilities. That flexibility, however, is also what makes the C-DSP 8x12 DL perhaps slightly less "plug-and-play" than most other processors on the market. Unfortunately, "auto-equalization" doesn’t mean "auto-configuration".

This document is therefore both a review and a practical setup guide, with a stronger emphasis on the latter. Rather than focusing solely on subjective impressions, the goal is to document a real-world configuration process and explain the rationale for certain choices, especially when Dirac Live is involved. The intent is not to present a single "correct" way to tune a system using the C-DSP, but to provide a clear, defensible workflow that we can adapt to our own vehicles, systems, and listening preferences.

AV NIRVANA has traditionally leaned more toward home audio, home theater, room correction, and related technologies than car audio. However, we do have our 12 Volt Mobile Audio Nirvana forum for those of us who enjoy tinkering with mobile audio. The common thread here is my long-standing appreciation for miniDSP and Dirac Live, both of which I have used extensively in my home systems and vehicles. That makes the C-DSP 8x12 DL a natural product for me to review, even if car audio is not AV NIRVANA's primary focus overall.

This review/setup guide also has a long history. I originally started working on it back in 2023 while using a C-DSP in my previous Ford F-150, but vehicle changes and system changes put it on hold for quite a while. After returning to Ford in late 2025, I initially tried an all-Audison approach with the Accordo system, hoping it might satisfy what I was looking for. It did not take long for me to realize how much I missed the miniDSP-Dirac Live combination. That revived this review/setup guide, and after several more months of writing, it finally came together.

While this review/setup guide is lengthy, it does not have to be read strictly from beginning to end. It can also be used as a reference when only one part of the setup or calibration needs to be learned or revisited. If a quick refresh is needed for a particular step or setting, the Index and Roadmap links should make it easy to jump directly to that section.

One feature that sets the C-DSP 8x12 DL apart from nearly every car-audio DSP I’m aware of is its integration with Dirac Live. While Dirac Live may not perform miracles and won’t fix a bad installation, it can address some issues that are difficult to fully resolve with traditional tuning alone. Many of the issues we experience in vehicles stem from overlapping drivers, phase rotation, and excess energy that lingers longer than it should. Dirac operates in both the frequency and time domains, allowing it to tighten bass decay, improve transient clarity, and clean up crossover behavior in ways that simple EQ and delay adjustments may not fully accomplish. It isn’t fixing the vehicle… it's fixing the system’s bad habits inside the vehicle. Dirac can make a system sound cleaner and tighter and is generally more consistent than manual tuning alone. As some have suggested, it might even give us that "spaceship" sound. For several years and across several vehicles, it has certainly helped my wife and me enjoy the best sound we’ve ever experienced in a vehicle.

Owner's manual: C-DSP 8x12 DL User Manual


Features
  • 400 MHz 32-bit SHARC floating-point processor
  • Dirac Live technology helps tune the cabin environment
  • 32-bit DAC/ADC chipsets
  • THD+N 0.0007%, 115 dB SNR
  • Digital and analog inputs (Low/High levels)
  • Flexible DSP processing blocks, rear fill processing (L-R, L+R), thanks to internal matrix
  • Fully differential balanced inputs
  • Windows/Mac compatible GUI
  • Remote control or preset/master & sub volume control

Specifications
  • Digital Signal Processor Engine: Analog Devices ADSP21489 floating-point DSP
  • Converters: 32-bit AK4456 DAC / 32-bit AK5556 ADC
  • Internal Processing Resolution / Sample Rate: 32-bit / 48 kHz with Dirac Live processing
  • Input/Output Configuration: 8 inputs / 12 outputs
  • Audio Input Connectivity: High-level input via 6-terminal block, low-level unbalanced input via 6 RCA, stereo digital inputs via SPDIF coaxial and Toslink optical, supported ASRC from 44.1 kHz to 192 kHz
  • Audio Output Connectivity: 12 RCA outputs, 115 dB SNR, THD+N 0.0007%
  • Input / Output Max Levels: Input: 8 or 12 Vrms high-level / 4 or 2 Vrms low-level; Output: 4.5 Vrms
  • Input Impedance: High-level: 68 Ω / Low-level: 10 kΩ
  • Output Impedance: 560 Ω
  • Calibration Software: C-DSP 8x12 DL plug-in
  • Filtering Technology: Dirac Live + miniDSP speaker processing toolbox
  • DSP Presets: Up to 4 presets
  • Dimensions: 41 x 205 x 122 mm
  • Power: Isolated DC-DC conversion for car audio environment
  • Impulse Response Correction: Yes
  • Infrared Remote Learning: Yes
  • Windows/Mac Compatible: Yes
  • UMIK-1 Included as Bundled Option: Yes
  • Bass Management: Yes
  • Room EQ Wizard Support: Yes

Hardware and Features - A Closer Look
One thing that immediately stands out with the miniDSP C-DSP 8x12 DL is that its processing platform and measured performance are more serious than its price might suggest. On paper, the specs are legitimately strong. At the heart of the unit is an Analog Devices ADSP-21489 SHARC floating-point DSP, running at 400 MHz with 32-bit internal processing. That matters because Dirac Live and multi-channel DSP correction require real processing horsepower, especially when handling multiple channels, crossovers, delays, EQ filters, bass management, and impulse-response correction simultaneously. The converter section is also solid. The C-DSP 8x12 DL uses 32-bit AKM chipsets, specifically the AK4456 DAC and AK5556 ADC. Combined with a spec'd 115 dB signal-to-noise ratio and 0.0007% THD+N, the unit is clearly designed to be transparent in a serious car audio system.

The processor supports 8 inputs, with high-level speaker inputs, low-level RCA inputs, and digital inputs via SPDIF coaxial and Toslink optical. The output section provides up to 4.5 Vrms, which is sufficient to cleanly drive high-quality amplifiers. The unit does provide 12 analog outputs, but that needs to be understood in context. Dirac Live correction is limited to eight channels, with the additional outputs available through the post-Dirac output matrix. That still offers routing flexibility, but it does not mean the unit has 12 independently Dirac-corrected outputs.

The internal matrix enables flexible routing and processing, including L-R and L+R rear-fill, bass management, custom crossover design, PEQ, delay, and level control, all of which work well alongside REW-based measurement and verification. Add in four presets, remote control support, master/sub volume control, and Windows/Mac compatibility, and it becomes a very flexible tuning platform. With the SHARC floating-point processor, 32-bit AKM converters, above-average SNR, extremely low THD+N, a flexible input/output matrix, and Dirac Live correction, this unit belongs in the conversation alongside serious high-end processors. For what it offers, the technical package is hard to ignore. If there are any doubts about how clean this miniDSP unit is, check out Amir's measurements at Audio Science Review.


Review System/Equipment
  • 2025 Ford F-150 Platinum Plus (B&O Unleashed Audio System)
  • PAC AP4 FD32 Interface (Replaced Factory Amp)
  • miniDSP C-DSP 8x12 DL (Review Subject)
  • Helix Ultra S DSP
  • Helix Amplify 206 Direct Amp (Powering Dash Mids, Pillar Tweeters, and Rear Fill Speakers)
  • Helix Amplify 204 Direct Amp (Bridged - Front Door Midbass)
  • Helix P One MK2 Amp (Powering Subs)
  • Helix Conductor Pro (Control Knob for Sub/Midbass Level, Rear-Fill Level, and Ultra S Presets)
  • Stereo Integrity TM8 (8" Front Door Speakers 70-200Hz)
  • AudioFrog GB40 (3" Midrange Dash Speakers 200-2500Hz)
  • AudioFrog GB10CF (A-pillar Tweeters 2500Hz+)
  • AudioFrog TP-50V2 Tweeter Protectors (Mounted with the Tweeters)
  • Hertz MPS 300 S2 Mille Pro Series (Dual 12" Subs – MTI Acoustics Box)
  • Morel Virtus Nano Carbon MM2 (Rear Pillars - Rear Differential Fill 300-7 kHz)
  • ReKRAPEINNOS Noise Isolator by E.I.N.N.O.S. Labs
  • Planet Waves Custom RCA Cables
  • Acoustic Treatments (ResoNix CLD Damping/Absorption/Insulation, and SoundSkins Door Kit)

Why I Use the Helix Ultra S with the miniDSP
One thing that may stand out in my equipment list is that I am using the Helix Ultra S DSP along with the miniDSP C-DSP 8x12 DL. I wanted to keep Dirac Live in the system, but the miniDSP has a few practical limitations in a more complex active setup like mine.

The first issue is output allocation. My front stage and subwoofer setup requires 7 of the 8 Dirac Live calibrated outputs:
  • 1 output for the subwoofer signal
  • 2 outputs for the front door midbass drivers
  • 2 outputs for the dash midrange speakers
  • 2 outputs for the A-pillar tweeters
This leaves me stranded when it comes to rear fill, especially if I want to use my preferred rear-fill method of deriving both L-R and L+R signals. The issue is not that the miniDSP lacks physical RCA outputs. It has 12 analog outputs. The issue is that only eight channels pass through Dirac Live, and in a fully active 3-way front stage with subs, seven of those independent channels are already being used by the front stage and subwoofer. The remaining outputs can still be used via the post-Dirac matrix, but they must be derived from the existing Dirac channels rather than from additional, independent, full-range left and right outputs. Rear fill works best when it can be derived from an appropriate left/right signal and then processed separately with its own level, filtering, polarity, and delay. In my current 3-way setup, the available Dirac channels are already assigned to individual speaker bands: midbass, midrange, tweeters, and subwoofer. Since only one Dirac channel remains unused in my current setup, using the extra physical outputs would still mean deriving rear fill from channels that are already corrected, delayed, and shaped for specific front-stage drivers. That is not the same as having independent rear-fill processing available.

The miniDSP worked perfectly in my previous 2-way front-stage setup, where I used front-door midbass drivers and wideband dash speakers. That setup used fewer independent channels, leaving room to handle rear fill inside the miniDSP. Once I added dedicated tweeters and moved to a 3-way front stage, the system outgrew what I could cleanly do inside the C-DSP alone. That's one of the reasons I added the Helix Ultra S.

Because I wanted to keep Dirac Live as part of the main tuning process, my only option was to add a second processor. I did not want to use just any processor, though. I wanted something on a similar quality level to the miniDSP from a noise and distortion standpoint. In other words, I wanted a clean processor with excellent measured performance. The Helix Ultra S gives me the additional processing flexibility I need for rear fill while maintaining the quality level I want in my system. Another reason I chose the Ultra S is its compatibility with the Helix Conductor Pro, which gives me more control than a traditional bass knob. I can use it to control a low-shelf boost that affects more of the system than just the subwoofer level, and I can also control rear-fill attenuation from the driver’s seat, which makes rear-fill adjustment much more convenient.

The second limitation of the miniDSP for my system is the PEQ capacity. The miniDSP provides 10 PEQ filters per channel, which should be enough for many users. While not required, I like to use PEQ filters to reduce each driver’s response peaks before performing the Dirac calibration. I also use PEQ filters after the Dirac calibration for stepped low-shelf house curves on my subs, midbass, and midrange speakers, as I’ll discuss later in the setup process. The latter reduces the number of filters available for pre-Dirac peak reduction, which became especially noticeable when I was using wideband dash speakers. Those drivers had several response peaks that I wanted to reduce before running Dirac, and using too many miniDSP filters for that purpose left fewer filters available for my stepped low-shelf filters. Once I moved from widebands to a 3-way setup, the issue became much less severe, but I still prefer the current arrangement. The Ultra S allows me to handle those pre-Dirac peak cuts separately and treat them like a permanent "set it and forget it" correction layer. This frees up the miniDSP PEQ section for house-curve shaping and any other tuning work that may arise.

So, while the miniDSP C-DSP 8x12 DL is the subject of this review and remains the processor providing Dirac Live correction, the Helix Ultra S plays an important supporting role in my system. It solves the rear-fill limitation, expands the available PEQ resources, gives me low-shelf filter bass boost, and provides rear attenuation control. It gives me the flexibility needed for my particular installation without compromising the overall quality of the signal chain.

Ultimately, the miniDSP does have some limitations in my setup, and I know I am not the only one who has encountered the 8-channel Dirac output limitation in a more complex active system. In a 2-way front-stage system, the C-DSP 8x12 DL will likely be all anyone needs. In my system, I needed more routing and PEQ flexibility than the miniDSP alone can provide. However, the reason I continue to use it is simple... it gives me Dirac Live in a car-audio DSP, and that remains its biggest advantage. There are other processors that may offer more routing, more outputs, more PEQ filters, and a more modern interface, but they do not give me what I value most in this setup… Dirac Live correction.


Measurement Equipment/Software Used

Tuning Guide Recommendations
Several excellent tuning guides are available, though not all include the miniDSP unit. I don’t think any one of these represents a single, absolute, 100% "universally preferred" tuning method. Yet… each one is internally consistent, technically defensible, and very useful. We just have to keep in mind that each one also reflects the authors' assumptions, constraints, goals, and preferences, as well as the types of vehicles and systems around which they were written. A few of these guides that I recommend are listed below.
The miniDSP setup and tuning guide section of this review is written with enough detail for readers who may not be fully familiar with the C-DSP 8x12 DL, while still offering experienced users a practical workflow to compare against their own methods, revisit specific steps, or consider different approaches to Dirac calibration, APFs, and pre and post-Dirac configuration.

While I’ve written a couple of setup guides for the C-DSP, they're outdated. I felt it would be beneficial to prepare another guide with more options to consider. I also wanted to include the use of the All-Pass filter tuning method developed by Andy (oabeieo from the DIYMA - diymobileaudio.com forum), which many consider a viable and potentially better alternative to the standard 2-channel tuning method. This method has produced good results for many C-DSP users, including me. It is currently my preferred tuning method.

This guide outlines the step-by-step procedure I used for my 3-way front stage active system in my 2025 Ford F-150 Platinum Plus, which included the now-removed B&O Unleashed factory system. My setup includes rear subs (dual mono), front-door midbass drivers, midrange dash speakers, A-pillar tweeters, and rear-fill speakers. Dirac is used for the front stage and subs, while rear fill is handled separately through my Helix Ultra S DSP.

My system build thread: 2025 Ford F150 Platinum Plus B&O Unleashed (the leash broke again) - System Upgrade - The Sequel

This is in no way meant to take away from the Quick Tuning Guide for the C-DSP written by Anu2g at DIY Mobile Audio: MiniDSP C-DSP 8x12 DL (Dirac Live): Quick Tuning Guide

His guide is excellent, and I highly recommend reading it to become as familiar with the process as possible. The guide I am providing offers a slightly different outline, step-by-step images, and a few more options to consider, in addition to a review of the miniDSP unit. There will naturally be some overlap with his Quick Tuning Guide because some steps can only be done one way, and I don’t want to leave those out. Surely it can only help to have more methods to our madness.

This guide documents how I set up my system from start to finish. It reflects my vehicle, equipment, and listening preferences. There are multiple ways to approach this process, and the best approach will vary by system and goals. Use this as a practical reference, not a rigid rulebook. I will also share other options I have read about, although I may not have tested them all.


Required and Recommended Equipment
This equipment will be needed to set up the miniDSP and perform the Dirac Live calibration.
  • Microphone: USB is easiest, and the miniDSP UMIK-1 is available as an optional bundle with the C-DSP at a reasonable price.
  • Laptop: Best with at least two available USB connections, one for the microphone and one for the miniDSP. USB-C adapters or hubs may be needed, depending on the laptop.
  • 10-12’ USB Type A to USB Type B cable (printer cable): A longer cable makes it easier to connect the laptop to the miniDSP, especially if working outside the vehicle. It can also be permanently connected to the miniDSP and tucked away for future tuning sessions. The cable included with the miniDSP is only 1 meter, which may be too short depending on where the processor and laptop are located.
  • 13.8V 25-30 Amp Regulated Bench Supply/Power Supply: A 25–30 amp bench supply may be enough for setup and measurement work, especially if the vehicle tends to shut down or enter sleep mode. For extended listening at moderate levels without the vehicle running, a larger 100–200 amp supply may be needed.
  • USB Flash Drive / iPhone with CarPlay / Android device with Android Auto: A reliable playback method will be needed to play pink periodic noise or sweeps for measurements.

Required and Recommended Software
This software will be needed to set up the miniDSP and perform the Dirac Live calibration.
  • miniDSP Control GUI plug-in: Available under the miniDSP User Downloads section after purchase/registration of the C-DSP 8x12 DL.
  • Microphone calibration file: Download the correct calibration file for the microphone in use. For miniDSP UMIK microphones, the file is available from miniDSP by providing the microphone's serial number.
  • Dirac Live program: Available from Dirac after creating/logging into a Dirac account. I generally recommend using the latest version unless there is a known issue with a specific release. The Dirac username and password are required when the software first loads.
  • REW (Room EQ Wizard): Or an equivalent RTA/measurement program. REW is free and available through the REW Support Forum here at AV NIRVANA.
An Internet connection is required to log in to Dirac Live and complete the Dirac workflow.


A Few Words Before the Setup Guide
Before getting into the video and written setup guides, I think it is worth saying this plainly: there are many opinions on how to tune a car-audio system, how to use the miniDSP C-DSP 8x12 DL, and how to approach Dirac Live. Some of those opinions are based on experience, some on preference, and some on repeating what others have said. Car audio is not like biblical study, where we can point to book, chapter, and verse and settle the matter with authority. It has a subjective side; it is vehicle-dependent, system-dependent, and listener-dependent. What works well in one vehicle may or may not work well in another. What sounds excellent to one listener may not be what another prefers. Some people may say a certain method will not work, yet someone else may try it and get excellent results. That does not mean every idea is equally good, nor that measurements, acoustics, and good setup practices do not matter. They absolutely do. However, it also means there may be room for experimentation.

The method I describe in this guide is not presented as the only way to set up the miniDSP or the only way to use Dirac Live in a vehicle. It is simply the method I used, refined, measured, listened to, and found successful in my system... yet, it doesn't mean my method won't change. I encourage readers to understand the reasoning behind each step, but also to try different approaches when appropriate. I recommend caution in allowing someone to convince us that something cannot work or isn't good simply because they have a bunch of forum posts, YouTube videos, or a strong opinion. I'm not implying these are all bad or wrong. What I am saying is, if a method is tried, measured, listened to, and works well in our system, let's enjoy it. That is ultimately the goal.


miniDSP C-DSP 8x12 DL Setup Video Guide
Before diving into the setup process, I should mention that I have also created a companion video walkthrough that follows a similar procedure to that covered in this guide. Some people learn best by reading and working at their own pace, while others prefer seeing each step demonstrated visually. Neither format is necessarily better than the other, although the written guide will include more detail with explanations. In many cases, a particular concept may be easier to understand in the video, while other details may be easier to reference in the written guide. I recommend using both resources together when possible.



Set Up Roadmap and Quick Reference [Printable PDF]
This is the overall workflow I use when setting up the C-DSP 8x12 DL with Dirac Live. I reiterate: it is not the only possible method, but it keeps the process organized and helps avoid repeating a full Dirac calibration due to a routing, crossover, or center-image issue that could have been caught earlier. I use separate pre-Dirac and post-Dirac configuration files that I've created and saved. The pre-Dirac configuration is used to measure, optimize (PEQs if used), enter APFs (All-Pass Filters), and calibrate the system. The post-Dirac configuration is the final operating setup, with APFs removed, crossovers entered, rear-fill routing with delay (if used), house curve shelf filters (if used), and other final settings restored.

Note: Click on linked words/phrases to jump to that section of the guide for detailed instructions/explanations. The full index at the beginning will naturally be more complete.

First-Time C-DSP Setup
Let’s get right into setting up the C-DSP 8x12 DL as if the unit has just been connected for the first time. If already familiar with the basic C-DSP plug-in setup, skip ahead to REW RTA Measurements (Part 1).


C-DSP Initial Setup – Tabs and Menus
After downloading and installing the C-DSP plug-in and connecting the USB cable between the C-DSP unit and my laptop, the following screenshot shows what appears on my laptop screen. There are six highlighted and numbered points from this initial startup screen that I will discuss first.

1. The Inputs & Bass Mgt tab is the default tab after starting the plug-in. Notice that Config 1 is also selected. Config 2, Config 3, and Config 4 are shown to the right of Config 1. These are the four presets that can be configured in the plug-in and later selected with the remote.
2. Confirm the latest software plug-in and firmware versions.
[CLICK IMAGE TO ENLARGE]
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3. Click the Connect icon to connect the plug-in to the C-DSP unit.
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When the connection dialog box appears, select Restore Config because this is the first time using the unit. This resets it to the factory-default configuration. Clicking Help will explain the options in detail, as will the manual.
[CLICK IMAGE TO ENLARGE]
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Once connected, the menu options need to be set up. Across the top of the software plug-in program are menus labeled File, Restore, Display, Help, IR Remote, and Start Dirac Live Software. Some of these are self-explanatory, and additional details are available in the manual. The File menu allows saving and loading user-created C-DSP configuration files. The Restore menu allows restoring factory defaults and updating DSP firmware.
[CLICK IMAGE TO ENLARGE]
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The Display menu has several options. I select Show Delay in ms unit. Just click the desired preference… there is no confirmation. Select Show Delay in cm unit if distance measurements are preferred. Remote Power Settings allows setting the delays for the remote trigger-out and C-DSP power-off. I leave those at their default settings. If there is a power-on thump or noise, these settings may help. Under Subwoofer Channels Selection, I select Output7 as my subwoofer channel, which is the RCA output on the miniDSP that feeds my subwoofer amp.
[CLICK IMAGE TO ENLARGE]
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For Dirac Channels Configuration, I set those up as shown below. This is where I tell the miniDSP which speakers I’m using with Dirac Live. Each Channel corresponds to the appropriate RCA output on the miniDSP, and the Speaker Type indicates the speaker connected to the amplifier channel.
[CLICK IMAGE TO ENLARGE]
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The other menu items are Help (self-explanatory), IR Remote (use when using an IR remote alongside the wired remote), and Start Dirac Live Software (used to begin the Dirac calibration).

After connecting and configuring the menu items, the various tab sections need to be set up.


Inputs & Bass Mgt tab
This tab is shown at the beginning of the setup section above, and I'll continue with point 4 below this image. It shows the default view after connecting to the unit.
[CLICK IMAGE TO ENLARGE]
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4. If the unit is receiving its signal via the optical digital input (Toslink), click 0dB on Input1d through Input6d (far-right column) and set them to Off. The Toslink inputs are Input7d and Input8d. If using different inputs, leave those at 0dB and click the others to Off (button will turn dark gray). Typically, there are either two RCA inputs (Input1 and Input2) or Toslink digital inputs (Input7 and Input8) from a line converter or audio interface. PAC, AudioControl, mObridge, JL Audio FiX, and NAV-TV are a few examples. These devices take the speaker-level or digital signal from a factory head unit or factory amplifier and provide a usable signal for the aftermarket processor. In my wife’s car, I use an AudioControl unit with a C-DSP, so left and right RCA cables run from the AudioControl unit to Input1 and Input2 on the C-DSP. For my 2025 F-150, the PAC unit feeds the C-DSP’s digital optical Toslink input. Therefore, my Inputs & Bass Mgt tab is set up as follows.
[CLICK IMAGE TO ENLARGE]
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5. Click Input7 and Input8 to rename them as I did above (optional).
[CLICK IMAGE TO ENLARGE]
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6. Click the HPF and LPF buttons, link the left and right inputs (in my case, TOS-L to TOS-R), and set all four filters to Bypassed for now. After clicking on the HPF button for TOS-L, select TOS-R from the upper-left dropdown menu and then tick the Link box. It will prompt for confirmation and then change to Link Enabled. Make sure the Bypass Filter button is dark gray and showing Bypassed. If not, click on it to change it to Bypassed. Do the same for LPF. The LPF default is not bypassed, so it will show Bypass until it is clicked.
[CLICK IMAGE TO ENLARGE]
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Routing tab
Inputs are listed on the left side. I am only using the Toslink inputs, so I route the TOS-L input to all my left-channel speakers and the TOS-R input to all my right-channel speakers. The Dirac channels are listed across the top and should be assigned according to the RCA output connections. In my setup, Dirac 1 feeds the left dash midrange, Dirac 2 feeds the right dash midrange, Dirac 3 feeds the left front door midbass, Dirac 4 feeds the right front door midbass, Dirac 5 and Dirac 6 feed the tweeters, Dirac 7 is bass management for the subs, and Dirac 8 is not used.
[CLICK IMAGE TO ENLARGE]
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Dirac tab
This tab is for informational purposes only and displays the Dirac gain and delay settings after calibration. This will be shown after the Dirac calibration.


Mixer tab
This is where each Dirac channel is assigned to the appropriate speaker/output. Don’t confuse this left-side column with the Routing tab’s left-side column... they are different. The Dirac channels that appeared across the top of the Routing tab now appear in the left-side column of the Mixer tab. The top row of the Mixer tab contains the outputs/speakers, which can be renamed. Notice that Output1 in the first screenshot below has been renamed L DASH in the second screenshot. Output2 is R DASH, and so forth.
[CLICK IMAGE TO ENLARGE]
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All outputs at the top have been renamed to reflect the speakers connected to each output.
[CLICK IMAGE TO ENLARGE]
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To further clarify the difference between the Routing and Mixer tabs… the Routing tab assigns inputs to Dirac channels, so the Dirac channel for each speaker must be known. Remember, the speaker types were assigned earlier in the Dirac Channels Configuration section of the Display menu. The Mixer tab is where each Dirac channel is assigned to the appropriate output/speaker, which should match the Dirac Channels Configuration.

At this point, there is no reason to do anything with the other tabs. I’ll come back to those later. The initial setup is now far enough along to begin measuring each speaker individually and verifying the system’s behavior before any Dirac calibration is performed.


REW RTA Measurements (Part 1)
As alluded to earlier, this step is optional, but I do not recommend skipping it. At this stage, I want to check all my routing and mixing and measure what each speaker is naturally doing in the vehicle before I determine crossovers or perform Dirac calibrations. If, for some reason, I did not want to measure each speaker’s raw response, I could skip the next sections and move directly into the Dirac setup. However, measuring each speaker individually provides a great deal of useful information.

Raw measurements help confirm that every speaker is connected, routed correctly, playing from the proper channel, and operating within a reasonable range.

Raw measurements also show how each speaker behaves in its installed location, which is often very different from how the driver looks on paper. This makes it much easier to choose realistic crossover points, identify response peaks that may benefit from pre-Dirac PEQ, spot problem areas near the intended crossover regions, and avoid asking Dirac to correct a speaker outside the range where it should actually be used.

These measurements create a baseline. If something looks wrong after Dirac, after loading a different configuration, or after changing crossover points, I can compare back to the raw measurements and determine whether the issue is the speaker, the installation, the routing, the processing, or the calibration. Without that baseline, troubleshooting becomes more complicated.

The next sections will show how I use REW to measure the system before and after calibration, so this process is not limited to the pre-Dirac setup. It becomes part of the overall verification workflow. I want to know what the speakers are doing before Dirac, what Dirac changed, and what the final system is doing after the post-Dirac configuration is loaded.

As previously mentioned, the speaker’s measured response may also influence the crossover points. When choosing crossover points, I am not looking only at where a speaker can produce output. I also want to consider distortion, excursion limits, dispersion, and how smoothly the speaker will blend with the adjacent driver. A speaker may measure with usable output beyond the intended crossover range, but that does not always mean it should be used there. In general, I prefer crossover points that keep each driver within a comfortable operating range, avoid obvious breakup or roll-off behavior, and allow the final acoustic crossover region to sum smoothly.

Using REW (Room EQ Wizard) and either a UMIK-1 microphone or my mic array, I measure each speaker from 20 Hz to 20 kHz at my head-centered location using pink periodic noise. This can be done with a moving-mic measurement, a stationary microphone, or a mic array. I have used all three methods, although for this particular measurement, I prefer my mic array. Admittedly, in my truck, there are no major differences in the measured responses between these methods. Note: For this type of measurement workflow, sweeps are not practical for moving-mic measurements; pink periodic noise is the better choice.

I’ll refer mainly to the UMIK-1 for now. Connect the UMIK-1 microphone to the laptop and open REW. REW should prompt for confirmation of the mic selection and for loading the calibration file, which can be downloaded from the miniDSP website under User Downloads for the UMIK-1.
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After loading the calibration file, click Preferences in the upper-right corner to verify the input settings.

REW should show the UMIK-1 as the Input device, as shown below.
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Recording Pink Periodic Noise
REW’s Generator can be used to create a pink periodic noise file, which can then be saved to a USB flash drive, phone, or other playback device. I use my iPhone with CarPlay for playback in the vehicle. For what it's worth, I have compared the pink periodic noise recorded to a USB drive to my iPhone wireless to CarPlay. I measured no differences at various volume levels.

There are eight steps highlighted in the image below.
  1. Click the Generator at the top of REW to open the generator dialog box.
  2. Select the Noise tab.
  3. Select the Pink Periodic tab.
  4. I choose Custom because I do not want pink noise below 20 Hz during speaker testing in my truck. Set Filter Type to Brick and Sequence Length to 64K.
  5. Set the level units to dBFS and the level to -6 dBFS.
  6. Select Save to file.
  7. Select Mono, 48 kHz, 24-bit PCM, and set the duration to 10 minutes / 600 seconds, or whatever duration preferred.
  8. Click WAV (covered up by the watermark), then save the file to a USB flash drive or to the laptop for transfer to another playback device.
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Using Sweeps with an Acoustic Timing Reference
Periodic pink noise in REW’s RTA is sufficient for checking each speaker’s general usable range, identifying obvious response peaks, and determining reasonable crossover points. Sweeps are optional at this stage, but they can be very useful when checking timing, polarity, impulse response, phase, or distortion. I include this method here for those who want to use sweeps alongside or instead of pink periodic noise when appropriate. Keep in mind that sweeps do not work with moving-mic measurements, since the microphone needs to remain stationary during the sweep. However, sweeps can be used with a stationary mic… or with a mic array if using REW Pro.

Recording the Sweep
I use sweeps mainly to verify the other REW measurement functions mentioned above or to compare drivers. I first create the sweep in REW using the Generator function located in the menu across the top of the REW software window. I select Sweeps >> Measurement and verify the start and end frequency range, typically 20 Hz to 20,000 Hz, or whatever range I want to measure. For this example, I select Right only for the measurement sweep so that the sweep is recorded only on the right channel. This will make sense once the miniDSP routing is shown below. I then add the acoustic timing reference chirp to the left channel so that the timing reference is recorded only on the left channel. I save this sweep file and load it on my iPhone to play back through CarPlay. It could also be saved to a USB thumb drive or another device that can be played back through the vehicle’s head unit.
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My sweep file can be downloaded here: https://avnirvana.cc/REW/256kMeasSweep-RightSweep-LeftChirp.wav.zip


Configuring the miniDSP for Sweeps
These sweep measurements are primarily used for post-Dirac measurements, so I create or edit my saved post-Dirac configuration file, update the Routing and Mixer settings for sweep measurements, and save it under a different label. The REW sweep-based measurement functions are normally used after the Dirac calibration is complete, the crossovers are active, and any PEQ filters I plan to use are in place. I open my post-Dirac configuration file and adjust the Routing and Mixer tabs as follows.

The Routing tab is configured so that the left input, which carries the acoustic timing-reference chirp, is routed to Dirac 1. The right input, which carries the measurement sweep, is routed to Dirac 2.
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The Mixer tab is then configured so that Dirac 1, which carries the acoustic timing reference chirp, feeds only the left-front tweeter. In the sweep file I created, the timing reference chirp is a high-frequency signal, roughly 5 kHz to 20 kHz, so the reference channel needs to feed a speaker capable of reproducing that range. In my system, the left tweeter is crossed over at 2500 Hz, so it is the logical speaker to reproduce the chirp.

The speaker being measured is selected in the Dirac 2 row. For example, in the image below, I have selected L DASH. When the sweep file is played, the left tweeter emits the acoustic timing reference chirp, REW detects it, and then records the right-channel sweep played through the selected speaker.
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Once the sweep routing and mixer settings are correct, I save this as a separate C-DSP configuration file named POST-DIRAC-70-200-2500-XOVERS-Sweep-Config.xml. This keeps the sweep configuration available for future use without having to manually recreate or alter my normal post-Dirac listening configuration each time I want to use sweeps.


Measuring the Sweep with REW
Here is how the process works. I click the Measure button in REW, set the Timing dropdown menu to Use acoustic timing reference, and set Playback to From File. Next, I open the folder on my computer where the saved sweep file is located. I drag that file into the Sweep file window in REW. Once loaded, the file name appears below the Sweep file window.

With the recorded sweep file ready to play from my iPhone through the head unit, I click the Start button in the REW measurement window. After a few seconds, REW displays "Waiting for timing reference," indicating it is waiting for the acoustic timing chirp. I then press play on my iPhone. The sweep file plays; my mic picks up the chirp from the left tweeter, and then the measurement sweep plays through the selected speaker. At the end of the sweep, another chirp plays. Once the sweep is finished, REW displays the measurement in the analysis window.

Occasionally, REW may not detect the chirp correctly, or the sweep may not trigger properly. If that happens, I cancel the measurement, click Start again in REW, and replay the sweep file.
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RTA Setup
The image below highlights five sections for the RTA setup.
  1. Click the RTA icon.
  2. Click the RTA settings icon.
  3. Set the RTA settings as shown in the screenshot below.
  4. Click Appearance in the list.
  5. Uncheck the box next to Use bars on RTA.
Smoothing can be left at its default (No smoothing) if preferred. I use 1/6-octave because it gives me a clearer picture of the overall response I’m hearing while still showing enough detail to be useful. Setting the smoothing here is the same as changing it later in the Graph dropdown menu in the REW analysis window, so setting it here saves a step.
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Time to measure… almost. Before getting into the measurements, this is as good a place as any to discuss a somewhat controversial topic... microphones and measurement methods. There is just no escaping it, unfortunately.


Mics and Measurement Options
I didn’t realize how much there was to say about microphones until I finished this section. It is undoubtedly a crucial part of the tuning process. Reading tuning guides, watching measurement videos, and browsing forum discussions will quickly reveal strong opinions on nearly every aspect of the microphone. Yet… they are still just opinions… in my opinion, that is.

There are several microphones and measurement options… enough to make someone nauseous, confused, or both. I probably spent too much time on this, but I wanted to cover all the options because the information available varies widely.

The first consideration is the microphone itself. I’ve been using the UMIK-1 USB mic for several years, and it has remained consistent throughout. I did try a UMIK-2 at one point, but my StormAudio MK3 processor at home complained about it, and StormAudio’s engineer supervisor advised using the UMIK-1. The UMIK-1 has been very reliable.

Another option is to use an XLR measurement microphone with an audio interface if a more involved setup is desired. As my preferred option, I have the Audient EVO 16 USB audio interface with an Earthworks M23 G2 microphone, along with six Dayton EMM-6 microphones, all calibrated by Cross-Spectrum Labs, which I use in a custom mic array. User kaijerke at DIYMA (diymobileaudio.com) 3D printed mine for me.
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The next consideration is where the listener’s body will be during measurements. I have used several methods with a few different vehicles over the years. Mostly crew-cab trucks, but also my wife’s Lexus and a few other vehicles over the years. I have remained in the vehicle and started with the microphone tip at my nose, then moved it around my head for the other measurements. I’ve leaned the seat back, moved my head back out of the way, and taken measurements. I have measured from the outside of the vehicle, with a stiff mic snake wrapped around the headrest and the mic tip centered between my ears, where they would normally be while seated in the driver's seat. I’ve worn the JBL mic headset with the MS-8 measurement method. I’ve sat in the passenger seat and in the back seat using my boom mic stand. I’ve done all of these with the mic stationary, with moving-mic measurements, and now with my seven-mic array.

Currently, I’m using a string hanging from the roof of my truck. I got the idea from a post by steelwindmachine in the Dirac tips and tricks thread at DIYMA. Cal (Warden95) at DIYMA has confirmed this works reasonably well and makes it easier to position the mic tip correctly. I started with two strings, one at each ear position, then ended up with one string centered between my ears at ear height while I sit in the rear seat. This is my current preferred body position. My thinking is partly based on what Matt Trinklein, engineering supervisor at StormAudio, explained to me when I mentioned sitting in my listening seat while taking Dirac measurements in my dedicated home listening room. Although I stopped doing this in my room several years ago, I still asked Matt what he thought, and he strongly recommended following Dirac’s guidance: do not sit in the listening seat during measurements. I trust Matt, as he is one smart dude, though he primarily deals in the home-audio realm. Nonetheless, his reasoning applies to car audio with some adaptation… which I’ll explain next.

Dirac Live... and I’ll include Audison’s Accordo since I’ve also used it... appear to favor measuring without the listener sitting in the primary seat. At least, that is what I have inferred from the examples I have seen involving Dirac and Audison representatives. I have not found documentation clearly explaining why, but the practical reasoning makes sense to me. The listener’s body can introduce reflections, absorption, diffraction, and scattering that are not inherent to the vehicle or speaker system. Arms, legs, torso position/posture, clothing, and head location can all change from one drive to the next. Those changes can affect what the microphone measures, especially when the microphone is very close to the listener’s body.

I can think of several questions (with my answers) to consider when determining whether the driver’s seat should be occupied during measurements.
  • Am I at the same height every time I get in my truck? Not always… I adjust my rearview mirror from time to time because I may be more upright or more slumped from previous drives.
  • Are one or both hands on the steering wheel, and are they at the top, sides, or bottom? I mix it up.
  • If only one hand is on the steering wheel, is it the left or right arm, extended to the top, relaxed at the bottom, or resting with an elbow on the door rest or center console? It’s mixed.
  • My right foot is on the gas pedal when driving, so it would need to be on the gas pedal when measuring. What about my left leg? Is it stretched out and blocking some of the door speaker, or pulled back with my foot closer to the seat and not blocking as much of the door speaker? It’s mixed.
  • Am I wearing shorts or long pants, which may affect absorption? It’s a mix.
  • Am I wearing a short-sleeved shirt, a long-sleeved shirt, a thin jacket, or a thick jacket? Mixed.
  • If competing, am I the same size and height as the judge? It would matter. I don’t compete, but some do, and it should matter most to those who do.
This is why I prefer to keep the listener’s body out of the measurement area rather than ask the correction system to chase variables it cannot reliably fix. Its job is to get the timing right, keep things clean and tight, and make sure the system sounds right no matter how I sit. The goal is to measure and correct the loudspeaker-to-cabin interaction, not the variable presence of my body in a single temporary position. By removing myself from the measured area, I ensure the calibration is based on more stable and repeatable acoustic conditions. That gives the correction system a better chance of making timing and phase decisions that remain useful despite normal changes in seating position and posture.

It is understandable why some listeners prefer measurements taken while sitting in the driver’s seat. I’ve done it myself countless times over the years. At one time, I thought that including my body naturally incorporated the body-related and positional effects I was accustomed to hearing. From time to time, the results may even sound smoother, more relaxed, or at least more immediately pleasing when optimized with me at the wheel. However, this approach trades long-term consistency for temporary, listener-specific optimization, in which small changes in my body position, seat adjustment, or cabin conditions may undermine the accuracy of the correction.

Yeah, the rules can be broken… especially when tuning a personal vehicle, sitting exactly the same way every time, and only caring about how it sounds in that moment.

The main thing to keep in mind is that sitting in the seat during measurement not only corrects the system… it also bakes that temporary seating position into the tune. That is fine if that is the goal, but I do not see how it can be considered universal or easily repeatable, given the variables already mentioned. For most installations, especially those using time-domain-focused systems like Dirac Live, measuring without the listener in the primary seat seems to provide the most stable foundation for repeatable calibrations. Nonetheless… measuring while seated is easier, faster, and who doesn’t like to break the rules now and then? If someone has scored extremely well in competition using body-in-seat measurements instead of measuring from outside the vehicle, by all means, rule-breaking is king! However, if changes are needed after a competition, hopefully the exact seat position can be replicated; otherwise, it’s like a box of chocolates. Let’s also hope it’s the same judge for the next competition.

I admit… I’m a rule breaker myself because I don’t exit the vehicle. Just like I do at home, I get out of the way of the speakers and the mic. I sit in the back seat, use the arm of a boom mic stand to hold the mic, and move it as needed from inside the vehicle… or I use my mic array. My body is not interfering with any of the front-stage measurements. I feel like this is an acceptable way to break the rule, at least for me.

After the Dirac Live calibration is complete, it makes sense to sit in the driver’s seat to verify the overall response and evaluate listener interaction. Measurements taken with the vehicle unoccupied (or the body out of the way) reflect the system's behavior, while measurements taken with the listener present illustrate how body position and posture influence the perceived response. Yet, I still prefer to remain in the back seat for verification measurements. My truck, my preference.

Microphone placement must also be considered for the Dirac calibration. In the past, I have measured with the mic at a single point and at multiple positions. I have tried both approaches and have noticed differences, but nothing significant or alarming enough to say one method is unusable. Nonetheless, I still usually take 7-9 measurements around the head area in my vehicles. In my home listening room, I have compared the post-measurements of both exhaustively, and several of us home audio enthusiasts have listened ad nauseum. We believe the single-point mic measurement offers the best imaging, soundstage, and depth acuity. There are in-depth, reputable studies showing that single-mic-position measurements can perform best in some rooms (provided upon request), and mine appears to be one of them. However, when I’m in my comfy chair listening to music at home, I’m usually set and do not move much, and I can literally be that way for hours. My seating position from day to day is also much more consistent. The room is also large, with no nearby boundaries, unlike in a vehicle. In my truck, I move around much more. I definitely move my head and body more while driving than when I'm sitting at home, and the boundaries are undoubtedly closer.

I use moving-mic measurements or my mic array for pre-Dirac corrections and sometimes for post-Dirac verification, which do not perfectly align with a single-point Dirac calibration position. Granted, they won’t be perfectly aligned, but we are looking at averages around the head area. If a single-point mic position is used for one calibration, the mic position on the next calibration may differ slightly, and the results may vary, especially in a vehicle. In my truck, the differences have not been large, but the possibility remains. Interestingly, Audison appears to approach this differently from Dirac, as Accordo uses a single-point mic measurement for calibration… and it only measures once. I’d be curious to know their reasoning behind this decision. Granted, they are very different systems. I’ve used both, and Accordo is pretty good, just not as good as Dirac in my opinion. I have asked Audison support on multiple occasions, but have yet to receive a response. For the record, I’ve never had any issues getting responses from miniDSP.

For driver-only tuning, I prefer keeping both Dirac measurements and REW moving-mic measurements tightly clustered around the midpoint between my ears. This is also how my mic array is set up. This position best represents my binaural listening location, and limiting movement to a small area helps avoid averaging in seat positions I do not actually use. This comes down to preference, and another reason for more presets for testing.

Either way, it is essential to get the first measurement dead center in the head area to ensure proper timing and levels.

There is also the question of microphone orientation. Most seem to point the microphone up toward the roof and use the 90° calibration file. Others point the mic toward the front with the 0° cal file, while some point it at a 45° angle (or slightly forward) and use the 90° cal file. Again… vehicle, equipment, and preferences are all variables.

It all comes down to what works best for the listener, the vehicle, the system, and the desired outcome. As always, I recommend trying different techniques and deciding which one produces the best results.


REW RTA Measurements (Part 2)
Picking back up with the actual pre-Dirac REW RTA measurements... as previously mentioned, a USB drive, phone, or other reliable playback device can be used to send the pink noise through the vehicle’s normal playback path. I use my iPhone with CarPlay to toggle the pink noise on and off, which is more convenient since I’m in the back seat. Sweeps with an acoustic timing reference can also be useful, as referenced previously. Using periodic pink noise with REW’s RTA is sufficient to evaluate each speaker’s general usable range, choose reasonable crossover points, and identify peaks for potential PEQ filters.


Speaker Protection
Before running any full-range sweeps, pink-noise measurements, or Dirac sweeps with the normal crossovers defeated, speaker protection should be considered carefully. This is especially important for tweeters, since they can be damaged if low-frequency content is sent to them without protection. In my system, I use AudioFrog TP-50V2 tweeter protectors, which provide an added layer of protection during measurement and calibration. With a similar method, tweeters should be protected by an inline capacitor, a tweeter protection device, an amplifier high-pass filter, or another appropriate method before full-range measurements are performed.

If using a ported subwoofer enclosure, an appropriate infrasonic high-pass filter, often called a subsonic filter, should also be considered to protect the subwoofer below the enclosure’s tuning frequency. My subwoofer enclosure is sealed, so this was not required for my setup, but it is something ported-enclosure users should consider before running measurements.

Caution: Before measuring, amplifier gains and signal levels should be set appropriately to prevent the system from clipping prior to REW or Dirac measurements.


Background Noise Measurement
Before measuring the speakers, it can be useful to take a quick background-noise measurement with the system silent. With REW’s RTA window open and the microphone in the measurement position, leave the pink noise or sweep track stopped (off), keep the vehicle and system as quiet as possible, and click the RTA record button. Let REW average for a short period, then click Current to save the measurement. This provides a reference for the vehicle and measurement environment before any speaker signal is played.

This background-noise measurement can help reveal possible problems such as HVAC noise, outside noise, hum, grounding issues, or other sounds that may affect the speaker measurements. Once the speaker measurements begin, the playback level does not need to be excessive, but it should be comfortably above the noise floor so the speaker response is clearly being measured rather than the vehicle or environment.

It is also worth listening for system noise with no music playing. If tweeter hiss or other system noise is noticeable, the gain structure should be reviewed before final calibration. In most cases, it is better to address the source of the noise first, then rerun the Dirac calibration after the gain structure has been corrected. Adjusting amplifier input sensitivity after the system has already been tuned can change channel balance and may affect calibration, especially if the adjustments are neither measured nor repeatable.


Speaker Selection
For RTA measurements with periodic pink noise, select the speaker to measure in the Mixer tab of the miniDSP software plug-in, then turn off all speakers that are not being measured. The image below shows L DASH as the only active speaker. Click the block corresponding to each speaker to toggle it on or off.
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With the mic ready, start the pink noise and adjust the volume accordingly. There is no reason to play it super loud… around 75-85 dB usually works well for me. REW’s SPL meter is handy for SPL levels if needed.

The image below highlights three sections that explain how to measure using the RTA and how to view that measurement.
  1. Begin playing the pink periodic noise, then click the red record button to start recording.
  2. For moving mic measurements, I move the mic around the area where my head would normally be positioned and continue recording until the measurement response stabilizes. This may require 100 or more averages. Once the response has stabilized, click the red record button again to stop recording.
  3. Click the Current icon to send the measurement to the REW analysis window.
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The image below shows the measurement in the analysis window with 1/6-octave smoothing applied. Viewing these measurements with 1/6-octave smoothing gives me a clearer picture of the overall response I’m hearing and makes it easier to determine the speaker’s capabilities, potential crossover points, and any PEQ filters that may help reduce significant peaks in the response. Smoothing does not change the saved measurement data; it only changes how the response is displayed.

It is also helpful to name measurements clearly when saving them in REW. After several speakers, crossover tests, PEQ changes, or Dirac comparisons, it becomes easy to forget which measurement represents which condition. Simple labels such as LF DASH raw, RF DASH PEQ, LF DOOR post-Dirac, or Left side combined can make later comparison and troubleshooting much easier.
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The image below illustrates the difference between a fixed-mic measurement and a moving-mic measurement. The differences are minor for this particular speaker in my truck. This may not be the case with every speaker or every vehicle.
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Optional near-field measurements can also be helpful for troubleshooting. Measuring close to each driver will not represent what is heard at the listening position, but it can help confirm whether a response issue is coming from the driver or installation rather than the cabin. If a strange dip, peak, or roll-off appears in the listening-position measurement, a quick near-field measurement may help determine whether the issue is acoustic, installation-related, or coming from the driver itself.


To PEQ or Not to PEQ
Pre-equalizing each speaker before running Dirac is generally accepted as a reasonable approach and can be helpful when done carefully.

For pre-Dirac PEQ, I use the filters to knock down peaks only… no boosting.

I see PEQ as a cleanup step. The goal is to reduce obvious peaks in each speaker’s raw response before running the Dirac calibration, not to force every speaker to be perfectly flat. This gives Dirac a cleaner starting point, helps preserve headroom, and makes it easier for the measured response to fit the target curve without unnecessary boost. It can also be helpful near intended crossover regions, where I may not want Dirac to preserve or increase a driver's output in a range where that driver will ultimately not be used.

Cutting peaks does not create unlimited headroom, and any increase in playback level still uses headroom. The advantage is that the system is no longer limited by narrow response peaks or unnecessary boosts in areas that may not be correctable. In practice, this usually leaves more usable headroom where it matters and gives me more control over where any intentional boost is applied later.

The next response graph shows the L DASH speaker before and after applying cut-only PEQ filters to reduce the peaks.
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When examining the peaks, I can use the cursor in the REW analysis window to determine the approximate center frequency, estimate the required cut, and estimate the bandwidth/Q. The filters can then be adjusted and remeasured until a satisfactory response is achieved. However, there is a much easier method, which I'll discuss next.
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Room EQ Wizard EQ
While PEQ filters can be determined manually, REW has an EQ feature that works very well for this process. I created a short video showing how to use the REW EQ function. The written instructions are below the video. The video follows the same general process as the written instructions, though some of the speaker examples differ. Together, they provide more examples.


For the written instructions, I used an older measurement of a front dash wideband speaker to show how the EQ function works in REW.

Once I've completed my measurements in REW, I view them in the REW analysis window. I select a single speaker measurement to be EQ’d. Then I select the EQ button at the top of REW.
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Once the EQ button is clicked, the EQ window loads with the selected speaker measurement. On the right side are the expandable sections for the various EQ settings. I use Generic EQ in REW for this example. REW’s EQ filters can also be exported and imported into some DSP software, depending on the processor and supported filter format. I later realized this can be done with Helix DSP software, which can save a lot of time compared with manually entering each filter’s frequency, gain, and Q value. If the DSP being used supports REW filter import, this is the route I would recommend.

In the Target Settings section, I select Full range speaker for Target type. All the settings are fairly straightforward. I load the same House curve I use in the Dirac calibration, so the REW target follows the response shape I’m working toward. The Target Level (dB SPL) needs to be set based on the desired amount of cut. I would advise caution in creating too many filters. Remember, there are only 10 PEQ filter slots for each output channel in the miniDSP. This is one area where an additional processor can be beneficial, and it is one reason I use the Helix Ultra S. For this example, I clicked Calculate target level from response to get an estimate from REW, but the target level can still be adjusted manually as needed. This measurement looks low because the mic was not calibrated in REW for this example, but it is fine for showing how the EQ feature works.
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Next… expand the Filter Tasks section and set the desired EQ frequency range. For this example, I set the range from 100 Hz to 20,000 Hz. Note that I leave Individual Max Boost and Overall Max Boost set to 0 dB, since I do not want REW to create boost filters for pre-Dirac PEQ. The Flatness Target will generally be from 1 dB to 3 dB, depending on how aggressive the correction should be. Once these are set, I click Match response to target.
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Initially, with a Flatness Target of 1 dB, I get 11 filters. Clicking the EQ Filters at the top of the window opens the EQ Filters window, where I can view the filters.
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Changing the Flatness Target to 3 dB lowers the number of filters needed to 8.
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Moving the target curve up also reduces the number of filters to 5. I adjust these settings to get the number of filters I’m willing to use and the correction aggressiveness I want.
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Remember, this example is using a wideband speaker. When using separate midrange speakers and tweeters (as in the video), the number of filters needed will generally be lower. Either way, REW’s EQ tool can make it easier to generate precise PEQ filters. Naturally, after the filters are entered, I measure again to verify the results. I have had excellent results using REW’s EQ tool for this purpose… it is spot on!


Entering PEQ Filters
Below is an example of how filters are entered in the Outputs 1-6 tab under the PEQ section for the L DASH speaker. The settings for filter slot 2 are shown in this example. Again… these are merely examples and are not necessarily based on the measurements above.
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There are 10 PEQ filter slots available for each output channel. The available filter types are PEAK, LOW_SHELF, HIGH_SHELF, and ALL_PASS, as labeled in the software plug-in. There are six slots used for the L DASH speaker in this example.


Setting Levels and Timing Pre-Dirac
After the pre-Dirac PEQ filters are entered, I like to measure each speaker again and get the levels as close as possible before running Dirac. This step is optional, as the Dirac calibration will set its own gains during calibration, but I prefer to give it a more balanced starting point. If planning to set levels, do so after any pre-Dirac PEQ is applied. If the levels are set first and PEQ is applied afterward, especially when cutting several peaks, the speaker’s effective level can change. That means the level matching done before the PEQ may no longer be as accurate. Since the purpose of pre-Dirac PEQ is to clean up the speaker’s response before calibration, it makes sense to set or verify the levels after that cleanup is complete. I’m not chasing perfect level matching at this stage. I simply want each speaker to be in the same general range so the Dirac calibration doesn't start with one channel much hotter or much lower than the others. This can help keep Dirac’s gain adjustments more reasonable and may also reveal a possible issue with amplifier gain settings, routing, or output level settings.

I also like to have the speaker timing in the same ballpark before running Dirac. Again, this is not required because Dirac will calculate and apply its own delay settings during calibration, but I prefer to avoid starting with a system that is obviously misaligned before the measurement even begins. In my system, just as I did for the PEQ filters that tame my pre-Dirac peaks, I also set the speaker distances and levels in the Helix Ultra S.

I do not view this as a replacement for Dirac’s gain or timing correction. It is simply preparation. Just as I prefer to reduce obvious response peaks before Dirac, I also prefer to have the levels reasonably close and the speakers time-aligned enough to give Dirac a sensible starting point. The goal is to make Dirac’s job easier and keep the final gain and delay adjustments more reasonable and predictable. This is also useful when comparing multiple Dirac calibrations.

This may all seem a bit trivial, but if the pre-Dirac levels and timing are consistent, differences between calibrations are more likely due to mic position, speaker grouping, target curve, or curtain settings rather than basic setup changes that happened between runs.

Used within reason, I have not found that pre-Dirac level matching, timing adjustments, and modest pre-Dirac PEQ cuts have caused any adverse effects.

They simply help Dirac begin from a more consistent and better-controlled starting point. In other words, Dirac will not be surprised at what it sees.

I use REW’s RTA and pink periodic noise to check each speaker one at a time, using the Mixer tab in the miniDSP software plug-in to turn speakers on and off as needed. Once the levels are reasonably close, the timing is in the ballpark, and the response appears acceptable, I proceed to the first Dirac calibration run.


Dirac Live Calibration – First Run
This first run consists of a single measurement from the center-of-head position, mainly for informational purposes. This is also not a required step, but I find it useful before committing to a full Dirac Live calibration. It lets me review Dirac’s initial gain and delay decisions, study the measured response of each driver again, and verify the pre-Dirac level, timing, and PEQ work directly, all in Dirac rather than REW alone.

It also lets me check whether the center image is where I expect it to be.

If the center image is not right, it is much easier to adjust the mic position, rerun one center-position measurement, and listen again than to complete a full multi-position calibration, load the post-Dirac configuration, start listening, and then realize the center image is not where it should be. Center imaging can also be checked by speaker groups. For example, the tweeters, midrange speakers, and midbass drivers can each be listened to separately to confirm that no individual band is pulling the image noticeably left or right before evaluating the full front stage together.

If the center image is noticeably off during this first Dirac test run, I do not immediately assume the solution is to adjust the delay manually. Before changing anything, I first want to confirm the basics: routing, polarity, speaker assignments, levels, and microphone position. A poor center image can be caused by something as simple as a wiring or polarity issue, a level mismatch, an incorrect channel assignment, or the mic not being centered. Once those basics are confirmed, small changes to the measurement position or pattern can be evaluated with greater confidence.

In systems where rear fill or a center channel is connected directly to the miniDSP and included in Dirac, this first run can also provide useful starting points for delay and level settings. For example, the rear-fill speakers may later be manually adjusted with additional delay and lower levels, so Dirac’s initial delay values can provide a reference point. The same idea applies to a center channel if one is used. In my current setup, however, the rear-fill speakers are handled separately through virtual channels in the Helix Ultra S, and I no longer use a center channel. Therefore, the rear speakers and center channel are not part of my Dirac calibration at any point. For my system, this first run is mainly about measuring the front stage and subs... midbass, midrange, tweeters, and subwoofers. I manually measure and EQ the rear-fill speakers in the Helix Ultra S, but they remain outside the Dirac calibration.

Caution: As mentioned earlier in the Speaker Protection section, make sure the tweeters are protected before running full-range measurements or Dirac sweeps with the normal crossovers defeated. The all-pass filter method allows Dirac to measure the speakers without the final DSP crossover filters active, so tweeter protection should not be overlooked.

If any part of the following setup process is unclear, be sure to refer to the miniDSP C-DSP Setup Video Guide. Some procedures, such as routing, mixer assignments, measurement setup, and Dirac configuration, are often easier to understand when seen in real time. The written guide provides a structured reference that is easy to revisit later, while the video shows the workflow exactly as it was performed.


Start Dirac Live Software
I have Dirac Live downloaded and installed on my laptop. I generally prefer to use the latest version unless there is a known issue with a specific release, since updates are fairly frequent.

The microphone is connected to the laptop and positioned at the center of where my head will be in the driver’s seat. I use the string and my seat memory to make it easier to position the mic consistently. In the C-DSP software plug-in, I click Start Dirac Live Software in the menu bar at the top.
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Dirac starts up and displays the C-DSP as the processor to be used with Dirac Live, which I select. The Dirac version is shown in the bottom-left corner of the program, along with the login status. On first use, a Dirac login prompt will appear. A Dirac account is required, and the username (usually an email address) and password will be requested on first use. Subsequent sessions on the same computer will automatically log the user in. An Internet connection is required to use Dirac Live.
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Select Recording Device
Clicking the miniDSP in the center of the screen opens the first page of Dirac. I select my microphone and load the calibration file saved on my computer. Once loaded, it does not have to be reloaded in future sessions.
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Once the mic is selected and the calibration file is loaded, click Proceed to Measurement Levels in the bottom-right corner (covered up by our watermark) to open the Measurement Levels screen


Measurement Level Settings
The idea here is to get the sweeps loud enough for Dirac to make a valid measurement without playing them louder than necessary. Generally, 16–24 dB is sufficient, assuming the vehicle and surroundings are quiet. Clicking any of the play buttons below each speaker will play pink noise. I raise the Master slider on the far left to a level sufficient for measuring (typically 32 dB), then play each speaker and adjust the individual sliders until they are in the same general range. They do not have to be perfectly equal. If more output is needed, the red lock can be unlocked to raise the Master slider farther. In most cases, 0.00 dB for mic gain should be sufficient, although it can be increased if needed.
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Once the levels are set, click Proceed to Select Sweet Spot.


Sweet Spot
I select the Focused sweet spot for the driver's seat calibration. I only want to correct around my head. If tuning for both front seats, I would select Wide.
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Next, I select Proceed to Measure in the bottom-right corner (covered up by the watermark), which opens the Measure window.


Measurements
To start the measurement sweeps, I click Measure selected position. The sweeps will begin and run through all enabled speakers. Dirac recommends nine measurements with the microphone placed around the general head area. I discussed alternate opinions and theories in the Mics and Measurement Options section. It is important for the first measurement to be centered on the head area for proper center imaging.

If this is the first run of the Dirac Live calibration, I will complete only one measurement, as discussed earlier in the Dirac Live Calibration - First Run section.
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Once finished, the completed measurements are displayed for each speaker.
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I click Proceed to Filter Design in the bottom-right corner (covered up by the watermark).


Filter Design
This screen may look odd at first, and there are several steps to work through before the filters are ready to export. This is where the video may be more helpful, but I’ll do my best to explain it.

The window below shows the default position of the correction curtains, the default target curve, and the default speaker groups in the right column. The curtains control the frequency range that Dirac will correct for each speaker or speaker group. Clicking and dragging the curtain lines allows me to adjust the correction range as needed. The curtains need to be set, the desired target curve and target level adjusted, and the speakers grouped, which I’ll explain next.
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Filter Design - Speaker Groups
I start by determining the speaker groups. By default, Dirac places all speakers in Group 1. In most active systems, I would recommend separating them into logical groups, typically left/right pairs by speaker type, with the subwoofer placed in its own group. For example, midbass drivers would be grouped together, midrange drivers would be grouped together, tweeters would be grouped together, and the subwoofer channel would be placed in its own group. This allows each group to have its own correction range while still using the same overall target curve across all groups. Each speaker group should follow the portion of the target curve that applies to its usable operating range.

One concern I have with the single-speaker-group approach is that Dirac may attempt to apply correction in frequency ranges where an individual driver will later be filtered out by the crossover. For example, the subwoofer correction curve in the image below (the blue line separates the two images) shows activity well above the intended 70 Hz low-pass region. A 24 dB/octave low-pass filter will greatly attenuate that range, so this may not cause an obvious problem, but it can still affect headroom and may slightly alter the final acoustic slope. I saw similar behavior with other driver groups as well, where correction extended into areas that would later be attenuated by the active crossovers. This is one reason I was more comfortable using multiple speaker groups and keeping each driver’s correction behavior closer to its intended operating range.
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This becomes even more important when using a traditional target curve with a built-in house-curve shape. With the flatter cut-target curve I use, the effect may not be as severe, as I primarily use Dirac to reduce peaks rather than add bass boost. This does not mean I avoid all boosts in the final tune. It means I prefer not to have Dirac apply the house-curve bass lift during the main calibration. I would rather apply the final bass lift afterward with broad, intentional PEQ filters that I can adjust and verify.

In practice, the measured difference between multiple-speaker groups and a single-speaker group was not dramatic in my truck. The comparison below shows that the overall responses were very similar. However, I still preferred the multiple-group approach because it gives me more control over each driver type and better aligns the correction behavior with each driver’s intended operating range.
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To create separate speaker groups, click and drag a channel outside the default group. In the image below, Dirac 1 and Dirac 2 are the left and right front-dash midrange speakers. If I click Dirac 3, which is the left front midbass speaker, and drag it outside Group 1, Dirac creates Group 2. Additional speakers can then be dragged into that group or outside existing groups to create additional groups as needed.

In my current setup, I use four groups: left and right midrange, left and right midbass, the mono subwoofer channel, and left and right tweeters. The screenshot shows Dirac 1 and Dirac 2 in Group 1; Dirac 3 and Dirac 4 in Group 2; Dirac 7 in Group 3; and Dirac 5 and Dirac 6 in Group 4. I have tried to get Dirac developers and engineers to let us rename the groups, but so far, that has not been an option.

Clicking the upper area of a group, where the small black arrow appears in the zoomed image below, displays the measured response of both front-dash midrange speakers in the larger window. Clicking Dirac 1 or Dirac 2 directly displays only that individual speaker.
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Filter Design - Target Curve
Before I set the correction curtains, I will create or load my desired target curve. In the window image below, notice the black arrow pointing to the green dot in the small black square. Clicking here changes the slider targets to control points. Each control point can be adjusted to create the desired target curve. What is shown below is the default. If I click the small black square with the green marks again, the target curve reverts to the slider style. The sliders can be adjusted from -3 dB to +15 dB, while the control points offer greater freedom to shape the curve. A decision needs to be made on which target curve to use. There are fifty-eleven flavors, that is for sure. Four different target curves can be used and saved to the four C-DSP configuration presets for comparison.
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Below is an example of me moving the points around. This is not representative of any specific target curve… just an example. When clicking a control point, the frequency and dB level are displayed. A control point can be deleted by right-clicking it, and a new control point can be added by right-clicking anywhere on the target curve line.
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I have my own target curves that I have created and use. These have been saved in the target curves folder for Dirac Live. I open the file and load it into all speaker groups to keep the target curve consistent across all groups. Below shows this process. After clicking All groups in the first image below, I select my TILT-0dB-9dB-stepped.targetcurve file that is shown in the second image. The third image shows the loaded target curve applied across all groups.
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Target Curve Options
There is a host of target curves available. I've tried quite a few of them, but prefer my own. Some readers are bound to ask... why am I using a tilted flat target curve instead of a traditional house curve? Maybe because I’m weird? Perhaps. But really, the reason is simple… as alluded to earlier, I prefer to make Dirac’s job easier by encouraging it to do more cutting and less boosting.

The measured response is characterized by peaks, dips, reflections, boundary effects, and cancellations. If the target curve is set too high, Dirac may attempt to raise the response to match the target. Some of those low areas may not be true deficiencies in speaker output. They may be caused by cancellations or acoustic interference, and boosting in those areas can waste amplifier power, reduce headroom, increase the risk of distortion, and still may not fully fix the problem. In other words, some dips persist after Dirac. By lowering the entire target curve as I do, more of the measured response naturally sits above the target. This allows Dirac to focus more on reducing peaks and smoothing the response rather than forcing unnecessary boosts in problem areas. It may also allow Dirac to make better magnitude and time-domain decisions in those difficult areas, rather than chasing a localized dip that may not respond well to a boost. In my experience, this generally makes the target easier to reach and results in a cleaner, more controlled correction. This approach also leaves more usable headroom after calibration. Once Dirac has done its work, I can add my preferred house curve afterward using controlled PEQ filters consisting mostly of low-shelf filters. Because the surrounding response has already been brought under better control, the final house-curve lift or overall level increase may make some of those dips less noticeable without having asked Dirac to force an unnecessary boost directly into them. That gives me more control over the final house curve for the bass boost. This does not imply that other target curves will not work; it is simply my preference. Bottom line… the target curve has to be determined by the system, the vehicle, and personal preference.


Filter Design - Curtains
The curtains in Dirac Live determine the frequency range over which Dirac applies corrections for each speaker group. Anything inside the curtains can be corrected by Dirac, while anything outside the curtains is left alone. This is important because my goal is not to force every speaker to follow the target curve across the entire frequency range. I prefer to correct each speaker only within the range where it is useful and will actually be used in the final system.

The dotted vertical lines indicate Dirac’s suggested correction range, but they are only suggestions. I adjust the curtains based on the driver’s intended operating range, measured response, crossover plan, and whether Dirac will mostly cut peaks or boost weak areas.

Using the all-pass filter method, the speakers are measured full range during the Dirac calibration because the normal crossovers are not active in the pre-Dirac configuration. Instead, all-pass filters are used to represent the phase behavior of the final crossover points. As a result, the curtains need to be adjusted carefully. For example, the dash midrange speakers may be intended to play from around 200 Hz to 2500 Hz, but the measurement may show a response beyond that range. The last image above actually shows this. I do not want Dirac trying to aggressively correct the speaker far below or above its intended operating range, especially if that range will later be removed by the post-Dirac crossovers.

My general approach is to place the curtains so that Dirac corrects the useful range of each speaker without chasing areas that should not matter. I also try to avoid placing the curtain in a way that encourages Dirac to add unnecessary boost. I am mainly looking for Dirac to reduce peaks and smooth the response within the speaker’s usable range, not force correction where the driver is naturally rolling off.

This is another area where judgment comes into play. The curtains do not have to match the final crossover points exactly, but they should make sense for the driver being corrected. In my system, I set the curtains based on the speaker’s measured response, the intended crossover range, and the areas where Dirac is still reducing peaks. The image below shows the curtains adjusted slightly beyond the speaker’s intended operating range, where useful peaks can still be reduced, while stopping before Dirac begins boosting roll-off or weak output that I do not intend to use.
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After setting up the speaker groups, setting the curtains, and confirming the target curve, I click Proceed to Filter Export in the bottom-right corner (covered up by the watermark).


Filter Design - Filter Export
To export the filter design to the miniDSP unit, I select the preset slot where the Dirac filter will be exported. This should match the C-DSP Config preset being used for the calibration. Once the correct slot is selected, I export the filter to the C-DSP. The same Dirac calibration could also be exported to multiple preset slots, or even all four presets, if desired. This can be useful when comparing different post-Dirac house-curve PEQ settings while keeping the same Dirac calibration as the foundation.
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Saving the Project
After exporting the filter to the C-DSP, I save the Dirac project file so it can be reopened later for adjustments if needed. This is different from exporting the filter to a miniDSP preset slot. Exporting loads the correction filter into the C-DSP, while saving the project preserves the Dirac measurement and filter-design work for later editing.
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Reconnecting to the C-DSP
After saving the Dirac project file, I exit the Dirac Live software and reconnect to the C-DSP in the miniDSP plug-in. This allows me to review the Dirac gain and delay settings and continue with the miniDSP configuration.
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Reviewing Dirac Calibration Results
Once reconnected, I can review the adjustments Dirac made to gain and delay. I can see that Dirac is enabled, the gains have been adjusted, and the speaker timing has been set as shown in the delay column. Since I level-match the speakers and set the distances in advance in my Helix Ultra S DSP, there is usually not much adjustment needed here. Apparently, on this particular setup, I did not do as well with the left front door midbass level in Dirac 3 as I would have expected. I would also expect the delay settings to shift somewhat because the dual subs are spaced across the rear of the truck, and Dirac is working to time-align the subwoofer response with the front stage.

I recommend saving a screenshot of the Dirac tab after calibration. The gain and delay values are not something most users will need to adjust manually, but they can be useful later for troubleshooting, comparing future calibrations, or confirming that Dirac is still seeing the system in a similar way after changes. The Dirac information is only shown when connected to the unit, so if I'm working offline with the C-DSP and need to reference the Dirac levels or delay, I have the saved screenshot.

This is also a good time to remember to set the Master Volume back to 0 dB. I admit there have been quite a few times when I forgot, measured the results, and then wondered why there was no volume. Naturally, I had forgotten to return the Master Volume to 0 dB.
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Remember, this is only the first basic Dirac run. I use it to study the speaker responses, review Dirac’s gain and delay decisions, confirm that the pre-Dirac level/timing/PEQ work looks reasonable, and listen for center image placement before moving on to the final calibration. If something looks or sounds wrong here, it is much easier to correct it now than after completing the full calibration and loading the post-Dirac configuration.

I do not see any reason to repeat the entire Dirac calibration process here for the sake of the guide, as this review is already quite lengthy. The complete process is also shown in my video, where I use four speaker groups: subs, midbass, midrange, and tweeters.


Preparing for Dirac Final Run
I’ve shown the miniDSP settings used before the first basic Dirac run, but the final run requires a little more planning. Some settings need to be in place before Dirac is run, while others need to be restored or changed after the Dirac calibration is exported.

This is where saved miniDSP configurations become very useful. Separate pre-Dirac and post-Dirac configuration files can be saved and loaded as needed, so the same settings do not have to be rebuilt manually each time. This is especially helpful once the crossover points, routing, speaker groups, and general tuning approach have been determined. It also makes future Dirac calibrations much easier because the starting point is repeatable instead of relying on memory.

Before getting into those saved configurations, it should help to explain the APF (All Pass Filter) method of tuning, since that is part of how I prepare my pre-Dirac and post-Dirac files. The APF method is not mandatory, but it is my preferred approach. If APFs are not being used, this section can be skipped, and the configurations discussed later can be set up to use the intended crossovers during the Dirac calibration instead.


Dirac Live Calibration – All Pass Filters Method
The APF tuning method is intended to improve phase behavior and summing across the crossover regions. Andy, known as oabeieo on DIYMA, explains the basic idea this way: "The idea is to use the allpass filter to cause a shift that is identical to the shift that the crossover will make." He also explains that after measurement, the all-pass filter is removed and the crossover is enabled, which can result in "linearized behavior across the crossover region".

The way I understand it, the APF method lets Dirac "see" a phase shift similar to what the final crossover will introduce, without actually limiting the speaker’s output with that crossover during calibration. After the Dirac calibration is complete, the APFs are bypassed, and the actual crossovers are enabled. The goal is better timing/phase behavior and improved summing through the crossover region once the system is in its final post-Dirac configuration.

APFs are set up in the miniDSP before running the Dirac calibration. The APFs are based on the desired crossover points, so the APF frequencies should match the crossover frequencies that will be used after Dirac. Crossover points need to be determined first, which is why the earlier raw measurements and the first basic Dirac run can be useful. Those measurements help show where each driver is comfortable before deciding where the final crossovers should be placed.

For my setup, the PEQ filters, gain, and delay for each speaker remain in place. These are all set in my Helix Ultra S DSP. The APFs that are needed pre-Dirac and then bypassed post-Dirac for my current system are set in the C-DSP as follows:
  • Sub output = 1 APF: 70 Hz
  • Doors (Midbass output) = 2 APFs: 70 Hz and 200 Hz
  • Dash (Midrange output) = 3 APFs: 70 Hz, 200 Hz, and 2500 Hz
  • Tweeters (High output) = 2 APFs: 70 Hz and 2500 Hz
The 70 Hz APF is added to each speaker because I am using Bass Management in the C-DSP. Once bass management is implemented post-Dirac, its crossover behavior cascades to the other channels. I do not use 2500 Hz on the sub or midbass channels because that crossover point is outside the intended range of those drivers. Likewise, I do not use 200 Hz on the tweeter channels.

Below is an example of where to set the APFs in the C-DSP. This example shows the LF DASH speaker with a 70 Hz APF set on the EQ1 tab with a Q of 0.7.
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All of my APFs are set to a Q of 0.7 for my LR24-type crossovers. The APF Q values for other crossover types are as follows:
  • BW18 - Set APF: Q = 1
  • BW24 - Set APF: Q = 0.865
  • LR24 - Set APF: Q = 0.7
  • LR48 - Two APFs: Q = 1.4 and Q = 0.5
There are also several ways to experiment with the APF method:
  • Add an APF for the Bass Management crossover point only.
  • Add APFs at the speaker crossover points, but not at the Bass Management crossover point.
  • Skip APFs altogether and run the Dirac calibration with the crossovers active.
I recommend trying as many options as time allows, saving them to different presets, measuring the results, and comparing. The APF method is my preference, but it is still only one approach. The best option may vary depending on the vehicle, speakers, crossover points, and Dirac's response to the system.


Pre-Dirac C-DSP Configuration
I have created and saved a C-DSP configuration file named PRE-DIRAC-70-200-2500-APF.xml.

Saving a dedicated pre-Dirac configuration is very helpful, especially if multiple Dirac calibrations will be performed. Once the input assignments, bypassed bass-management filters, routing, speaker labels, and APF filters are determined and set correctly, I do not want to rebuild those settings manually every time I run a new calibration. Loading the saved pre-Dirac configuration gives me a known-good starting point and helps prevent mistakes that could happen if those settings had to be recreated from memory each time.

This is especially useful when comparing different Dirac target curves, microphone positions, speaker groupings, curtain settings, or APF/crossover methods. Instead of wondering whether a routing change, an unlinked channel, or a forgotten filter affected the results, I can reload the same pre-Dirac configuration and know that the C-DSP side starts from the same baseline each time. It also keeps the calibration setup separate from the final listening setup. My pre-Dirac configuration is used for measurement and calibration. My post-Dirac configuration is used for normal listening after the calibration is exported. Keeping those two files separate makes the workflow cleaner, faster, and much less error-prone.

My saved pre-Dirac configuration file contains the following settings.


Pre-Dirac - Inputs & Bass Mgt tab
Per the C-DSP manual, the Dirac Live calibration should be performed first on the speaker and subwoofer channels, and the Inputs & Bass Mgt filters should be set up afterward: "To use this configuration, do a Dirac Live calibration first on the speaker and subwoofer channels. Then set up the Inputs & Bass Mgt tab with the high pass and low pass filters for the subwoofer crossover."

It has been mentioned that the Bass Management filters are not applied during the Dirac calibration. I have not taken the time to verify this myself, so I simply follow the order shown in the manual. For the pre-Dirac configuration, the HPF and LPF sections are bypassed within the Inputs & Bass Mgt tab. The HPF is bypassed by default, but the LPF is not. It is set to 100 Hz by default, so it needs to be bypassed. The Link Enabled status and Cut off frequency (Hz) settings will not matter here because this configuration is only used before Dirac. Once the Dirac calibration is complete, the post-Dirac configuration will be loaded, and this pre-Dirac configuration will not be used again unless another Dirac calibration is needed.
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Pre-Dirac - Routing tab
The left and right inputs are assigned to the appropriate Dirac channels. In my setup, TOS-L feeds the left-side channels, and TOS-R feeds the right-side channels, with the Bass Mgt channel assigned for the subwoofer output. This routing should match the speaker assignments selected earlier in the Dirac Channels Configuration menu.
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Pre-Dirac - Mixer tab
The speakers are labeled and activated to match the Dirac channel assignments. This confirms that each Dirac channel is feeding the intended output channel before the calibration is run.
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Pre-Dirac - Outputs 1-6 tab
All Xover settings are bypassed by default. The speaker labels shown here are carried over from the Mixer tab. For the pre-Dirac configuration, the PEQ sections are used to enter the APF filters. Detailed instructions are shown in the next steps.
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As a side note, I would recommend assigning the Dirac channels in a logical order whenever possible. For example, Dirac 1 and 2 could be midbass drivers, Dirac 3 and 4 could be midrange drivers, Dirac 5 and 6 could be tweeters, and Dirac 7 could be the subwoofer. The reverse order would also work. My order is somewhat jumbled because I originally used Dirac 1 and 2 for wideband dash speakers, Dirac 3 and 4 for midbass, Dirac 5 and 6 for rear fill, and Dirac 7 for subs. I did not want to recable the processors and amps just to satisfy my OCD. It does not really matter, but a logical order does make the setup easier to follow.

The focus here is on the PEQ sections. Each speaker needs the APFs set as previously determined. I’ll start with the dash midrange speakers.
  • Dash midrange output = 3 APFs: 70 Hz, 200 Hz, and 2500 Hz
Click the PEQ button to open the filter section. Since my APF filters are the same for the left and right dash midrange speakers, I can link the left speaker to the right speaker. This allows the APF filters entered for the left speaker to automatically carry over to the right speaker.

Caution: Do not link the speakers if PEQ filters are also being used in the C-DSP to knock down response peaks. Those peak filters will usually differ between the left and right speakers, so linking the channels would copy the filters from one speaker to the other, when they should remain separate. In my system, the pre-Dirac peak filters are handled in the Helix Ultra S, so I do not need to use the C-DSP filters for that purpose. That allows me to link the left and right speakers in the C-DSP for APF entry only. If PEQ peak filters are used inside the C-DSP, the APFs should be entered manually for each speaker rather than linking the channels.

The first APF is 70 Hz. I select the EQ1 button, set Frequency to 70 Hz, leave Q at 0.7, and select ALL_PASS from the Filter type dropdown menu.
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Next, I click the EQ2 button, set the Frequency to 200 Hz, leave Q at 0.7, and select ALL_PASS.
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I do the same for EQ3 and set it to 2500 Hz.
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I repeat the same process for the other speakers:
  • Sub output = 1 APF: 70 Hz
  • Doors, midbass output = 2 APFs: 70 Hz and 200 Hz
  • Dash, midrange output = 3 APFs: 70 Hz, 200 Hz, and 2500 Hz - (Completed above)
  • Tweeters, high output = 2 APFs: 70 Hz and 2500 Hz


Pre-Dirac - Outputs 7-12 tab
Since Output 7 is my subwoofer output, only one APF is needed here: 70 Hz.
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All tab settings for the pre-Dirac configuration are now complete. The only remaining item to verify is the speaker selection under Display >> Dirac Channels Configuration. The speakers selected here are the speakers Dirac will sweep during calibration, so each enabled channel must have a speaker connected and playing. If a channel is enabled but no speaker is present, Dirac will throw an error. In my case, all channels are selected except Dirac 8, which is set to Unused.
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Now that the pre-Dirac configuration is complete, this config file can be loaded before future Dirac calibrations. Remember, if a crossover point is changed, the corresponding APFs must be changed as well, and the updated pre-Dirac configuration file should be saved.


Pre-Dirac - Save and Label Configuration
Once the pre-Dirac setup is complete, I save the configuration with an appropriate label. I prefer a file name that includes the crossover/APF points so it is easy to identify later… hence PRE-DIRAC-70-200-2500-APF.xml.
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Post-Dirac C-DSP Configuration
Once the pre-Dirac configuration is loaded, I run the final Dirac calibration. See the Dirac Live Calibration – First Run section for more details… or see the quick steps below.
  • Start Dirac from the miniDSP top menu, select the microphone, set the measurement levels, and select the Focused sweet spot.
  • Measure the final center-of-head position and the other preferred mic positions.
  • Group the speakers, set the target curve, and set the correction curtains.
  • Process the filters, name the project, and export the Dirac filter to the appropriate preset slot. This should match the C-DSP Config preset being used, such as Config 1 or Config 2.
  • Close Dirac and reconnect to the C-DSP in the miniDSP plug-in.
  • Load the post-Dirac C-DSP configuration to the same Config preset used for the Dirac calibration.
If there is no post-Dirac configuration to load, the final operating settings must be configured manually. However, the post-Dirac configuration saves that manual work and is highly recommended.

Some may be curious whether the pre- and post-Dirac configurations interfere with the Dirac calibration. They do not. The miniDSP configurations and the Dirac Live calibrations are stored in separate areas of Flash memory. One does not overwrite the other. When a preset is selected, the C-DSP simply recalls both the miniDSP configuration and the Dirac filter together. This means the miniDSP configuration… routing, crossovers, PEQ, delays, levels, and related DSP settings… can be changed or reloaded without erasing the Dirac calibration. The reverse is also true… different Dirac calibrations can be loaded or compared without automatically changing the miniDSP configuration. So, while each preset recalls a miniDSP configuration and a Dirac calibration together, they remain separate internally. This makes it possible to experiment with different Dirac calibrations, different post-Dirac configuration settings, or different house-curve PEQ settings without automatically destroying the other side of the preset. Hence, the pre-Dirac and post-Dirac configuration files.

I will verify the calibration with measurements, but first, I need to load my post-Dirac C-DSP configuration so I can measure the system with bass management and crossovers enabled, without the APFs. I will explain those verification measurements after finishing the details surrounding the post-Dirac configuration.

I created and saved a C-DSP configuration file named POST-DIRAC-70-200-2500-XOVERS.xml, which contains the following configuration. These settings can be modified to accommodate any system.

NOTE: If the post-Dirac configuration is created by modifying the pre-Dirac configuration, all APF filters must be removed.


Post-Dirac - Inputs & Bass Mgt tab
Since I am using Bass Management for my subs, I enter the sub-to-midbass crossover filters here. My crossover points are 70 Hz, 200 Hz, and 2500 Hz. The 70 Hz crossover is handled in the Inputs & Bass Mgt tab. The HPF side applies to the main speaker channels, while the LPF side applies to the subwoofer channel. Since I used APFs with a Q of 0.7 for the 70 Hz crossover during the pre-Dirac configuration, I now set the actual crossover filter type to LR24dB.

For reference, the APF Q values that correspond to the crossover types are:
  • BW18 = APF Q of 1
  • BW24 = APF Q of 0.865
  • LR24 = APF Q of .7
  • LR48 = two APFs, with Q values of 1.4 and 0.5
I enter these settings for the left input channel, TOS-L, and link it to the right input channel, TOS-R. Once linked, changes made to either channel are automatically copied to the other. When the HPF settings for TOS-L are entered, they are automatically applied to TOS-R as well.
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I then repeat the same procedure for the LPF, as shown below.
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Post-Dirac - Routing tab
The routing is unchanged from the pre-Dirac configuration, but it still needs to be included in the post-Dirac configuration file. This ensures the same input-to-Dirac-channel assignments are preserved after the final operating configuration is loaded.
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Post-Dirac - Rear Differential Fill
The routing shown above is for my 3-way front stage plus subwoofer setup. With a 2-way front stage, I would not need as many Dirac outputs for the front speakers. That would free up Dirac 5 and Dirac 6 for rear fill. In that case, the rear-fill routing could be configured as shown below using the rear differential method. With this method, the rear-fill signals are derived from the left and right stereo channels, but each rear-fill pair is combined in mono with one side inverted in polarity. This creates a differential fill effect rather than simply playing a normal left/right copy behind the listener. In simple terms, common information shared across both channels tends to cancel out, while the differential information remains. That is the opposite of what is normally desired for the front stage, where center information should remain strong and focused.

A good example is sitting centered between the two rear-fill speakers and playing pink noise. When I tried this, I could barely hear anything and thought for a minute something was wrong… then I remembered the setup. The common signal was canceled as intended. The rear-fill speakers are not supposed to create a strong center image behind the listener. They should add spaciousness and ambiance without pulling attention to the rear.

In the miniDSP software plug-in, level and polarity can be changed by right-clicking the routing button. For this example, the rear-fill levels are reduced to -6 dB, with one side of each rear-fill pair inverted as required. The final rear-fill level still needs to be adjusted by ear. Rear fill should not draw attention away from the front stage. When set correctly, it should add a sense of space without making the rear speakers easy to locate. Proper delay would also need to be set in the Outputs 1-6 tab.
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Post-Dirac - Mixer tab
The Mixer tab also remains unchanged from the pre-Dirac configuration. The speaker labels and Dirac-to-output assignments are preserved, so each Dirac channel continues to feed the correct speaker output after the post-Dirac configuration is loaded.
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Post-Dirac - Outputs 1-6 tab
This is where the APF filters were entered for the pre-Dirac configuration. If the post-Dirac configuration is created by modifying the pre-Dirac file, the APF filters must be removed before entering the actual crossovers.
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This is also where the speaker crossovers are entered. I click the Xover button for the left dash midrange and set the HPF to 200 Hz and the LPF to 2500 Hz, with both filter types set to LR24dB. I also link L DASH to R DASH, so the same crossover settings carry over to the right dash midrange.
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Next, I click the Xover button for the left front door speaker and set the LPF to 200 Hz with the filter type set to LR24dB. I bypass the HPF because the sub-to-midbass crossover HPF is already handled in the Inputs & Bass Mgt tab. I then link LF DOOR to RF DOOR so that the same crossover settings carry over to the right-front door speaker.
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Moving on… I click the Xover button for the front tweeters, set the HPF to 2500 Hz with the filter type set to LR24dB, and link the left and right tweeter channels.
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1780370108699.png


As mentioned earlier, linking left and right channels is fine when the crossover settings are identical. However, if PEQ filters are used in the C-DSP to correct each speaker individually, the channels should not be linked, as the PEQ filters will usually differ from one side to the other. In that case, the crossover settings can still be entered manually for each speaker.


Post-Dirac - Outputs 7-12 tab
There is no crossover setting needed in the Outputs 7-12 tab for the subwoofer output because the subwoofer LPF is handled in the Inputs & Bass Mgt tab. The HPF and LPF in this particular Outputs tab remain bypassed. However, I do use the PEQ filters here to help shape my house curve rather than building that entire curve into the Dirac target. I’ll show that setup in the next section.
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Post-Dirac - House Curve with PEQ Filters (Outputs 1-6 tab / Outputs 7-12 tab)
Rather than creating my entire house curve within the Dirac Live target curve and rerunning the calibration whenever I want to adjust it, I prefer to build the final house curve using PEQ filters in the miniDSP. Most of these filters are low-shelf filters, although the subwoofer section may also use a peak filter depending on the response I am trying to shape. This lets Dirac handle the main correction work first, while the miniDSP PEQ filters provide the final house-curve layer afterward.

These post-Dirac filters may include a meaningful amount of boost, especially in the subwoofer range. However, the purpose is not to randomly undo Dirac’s correction or chase every small dip and peak after calibration. The purpose is to apply a deliberate house curve after Dirac has completed its main correction work. Dirac is still responsible for the primary calibration work: timing, impulse response correction, left/right matching, and smoothing the system toward the selected target. The C-DSP PEQ filters are then used as a controlled final house-curve stage. Some may argue that making PEQ changes after Dirac defeats the calibration, but I do not see it that way when the filters are used intentionally. There is a difference between using narrow filters to fight Dirac’s correction and using broader filters to shape the final house curve. I am not using post-Dirac PEQ to re-correct every speaker or undo the calibration. I am using it to adjust the house curve to my preference.

This also makes the tuning process much more practical. If I want more or less low-end weight, midbass impact, or warmth, I can adjust the C-DSP PEQ filters without going back into Dirac Live, redrawing the target curve, exporting a new calibration, and starting the listening process over again.

While this could certainly change, below are the two filters I am currently using and favoring for my subs after a lot of experimentation. EQ1 is set to a 30 Hz peak filter with a Q of 0.7 and 7.5 dB of gain. EQ2 is set to a 55 Hz low-shelf filter with a Q of 1.0 and 7.5 dB of gain. I use a peak filter at 30 Hz rather than a low-shelf filter to reduce the boost below 25 Hz, since the subs and their current location do not naturally produce much output below 25 Hz in my truck.
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1780370147805.png

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To achieve a gradual house curve and give my system a little more warmth, I also apply slight low-shelf filters to the midbass door speakers and the dash speakers. For the midbass door speakers, I have added low-shelf filters at 120 Hz, 240 Hz, and 480 Hz. In the image below, I have overlaid the 2nd and 3rd filters to keep them in a single image.
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For the midrange dash speakers, I have added low-shelf filters at 240 Hz and 480 Hz. Again, the 2nd filter is overlaid for a single image.
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Post-Dirac - Save and Label Configuration
Once the post-Dirac setup is complete, I save the configuration with an appropriate label in the same manner I saved the pre-Dirac configuration. I labeled this file as POST-DIRAC-70-200-2500-XOVERS.xml.


Post-Dirac Verification Measurements - REW
Now that I've finished the Dirac calibration and I am ready for the post-Dirac configuration, I want to verify the measurements of each speaker. I will not load my final post-Dirac configuration file for these measurements; instead, I've created another configuration named POST-DIRAC-70-200-2500-XOVERS-LOW-SHELF-DEFEATED.xml. This configuration is the same as my final post-Dirac configuration file, less the low-shelf house curve PEQ filters. Those filters are bypassed initially so I can see the exact Dirac correction based on my target curve. Then, later, I can load my post-Dirac configuration with the low-shelf PEQ filters and measure them if I so desire.

Having loaded the POST-DIRAC-70-200-2500-XOVERS-LOW-SHELF-DEFEATED.xml file, I will proceed to measure each speaker's response in the same way I did at the beginning. I will use REW’s RTA and the periodic pink noise file I created earlier. Once REW is loaded and the RTA screen is ready to record the measurement, I'll select the first speaker and start playing pink noise to capture it in the RTA window.

In the mixer tab, I'll turn off all but the LF DASH midrange speaker and measure it first. I could start with either speaker... the order is not critical.
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I then measure each speaker individually. Once finished, I can view all the measurements in REW. The image below shows the results of my subs and each speaker on my left side, front stage.
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I'll measure the left and right side speakers, then measure them as a combined group with LF DASH, LF DOOR, LF TWTR, and SUBS selected in the mixer tab. The second image shows the results of this measurement. Then I repeat the same measurements for the right side.
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While this result was initially quite good, I noticed a slight dip near the 200 Hz crossover region in the combined response. During Smaart verification, I found that lowering the dash high-pass crossover from 200 Hz to 180 Hz improved acoustic summation in that region (shown above). That change became part of the final post-Dirac configuration before I later experimented with additional Smaart-based delay adjustments.


Post-Dirac Verification Measurements - Smaart
In addition to the REW RTA verification measurements, I also used Smaart to take a closer look at what was happening through the crossover regions, including acoustic summation and phase alignment. This was my first serious run with Smaart, so I am not presenting this as an expert-level Smaart tuning guide. I was learning as I went, and after a shaky start, dumdum and doiter from DIYMA were extremely helpful in getting me pointed in the right direction. Their input helped me better understand the importance of setting the reference delay correctly and reading phase around the crossover regions.

My goal with Smaart was not to replace Dirac or to prove that I could manually tune the system better. I wanted to verify what REW magnitude response alone does not fully show... how the phase behaved through the crossover regions after Dirac, especially the sub-to-midbass handoff. I also wanted to make sure the post-Dirac house-curve PEQ filters, Helix Conductor Pro adjustments, and Helix tone-control processing path were not creating acoustic summation problems.

One thing I found during the process is that measurements must be taken with the system in the same state in which it will actually be used. That seems obvious, but it became very important in practice. In my system, the Helix Conductor Pro tone control still had an effect even when set to 0. It changed the measured timing/phase behavior enough that the Smaart reference delay had to be reset. In other words, if the tone control is normally active during listening, it must remain active during verification. I initially had it completely defeated, set the reference delay, and later turned it back on, and things went haywire in Smaart.

I initially used Smaart to verify the Dirac/APF tune. In my truck, the Dirac Live calibration process, along with the all-pass filter method used during the pre-Dirac configuration, appeared to do a very good job preparing the system for the final crossover implementation. Thanks again to Andy (oabeieo from DIYMA) for the idea for that approach. The sub-to-midbass handoff, which was my primary concern, was already summing well with the Dirac/APF tune. That was an important finding because it showed that Dirac and the APF method had not left me with an obvious crossover-region problem to fix.

The Smaart capture below is not intended to show every measurement I took or every variation I tried. It is included as a brief look at the raw Dirac/APF configuration and the crossover-region behavior I was most interested in evaluating. The main point was to assess whether the drivers were summing properly across the handoff regions and whether any obvious phase or timing issues remained after the Dirac/APF process. After verifying the crossover behavior, I also experimented with additional Smaart delay adjustments, which are included in the capture below.
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1782314289269.png


This was a separate exercise from the crossover change described earlier, in which lowering the dash high-pass crossover to 180 Hz improved the midbass-to-dash handoff. With the delay adjustments, I was able to make some of the phase relationships appear better aligned, particularly around the sub-to-midbass crossover. However, that did not automatically translate into a better overall result. In fact, the version with additional Smaart-based delay adjustments reduced some of the bass and midbass authority I preferred from the pure Dirac/APF tune.

The comparison graph below clearly shows the difference. Both REW measurements include my post-Dirac low-shelf house-curve filters. The pure Dirac/APF version retained more energy through the upper-bass and midbass region, while the Smaart-adjusted version was lower through much of that same range. That matched what I heard. The Smaart-adjusted version sounded less authoritative in the bass and somewhat affected the “bass up front” character I normally enjoy with the Dirac/APF tune. With the Smaart-adjusted version, I found myself turning up the Conductor Pro bass control much more than usual, but it still lacked the weight and fullness I preferred.
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1782314219405.png


Please do not mistake this for me suggesting that Smaart is a waste of time or that it cannot be used to produce an excellent tune. I also do not want this to come across as discrediting professional tuners. There are many experienced tuners who understand Smaart far better than I do, and I have no doubt a seasoned tuner may be able to produce a better manual tune than Dirac alone in many systems. There is certainly more to manual tuning than simply lining up phase traces at crossover points with Smaart. My point is only that, in my system and at my current level of experience, the additional Smaart-based delay adjustments did not yield better results. The pure Dirac/APF tune already summed well across the important crossover regions and retained the bass weight, front-stage integration, and overall tonal balance I preferred.

I cannot say every system will respond the same way to post-Dirac Smaart-based delay adjustments. What I can say is that in my 2025 F-150, the Dirac/APF tune already showed good acoustic summation through the important crossover regions, especially the sub-to-midbass handoff. Smaart was extremely useful for verifying that behavior and for helping me better understand what was happening through the crossover regions. However, after listening to and comparing the Smaart-adjusted version against the pure Dirac/APF version, the Dirac/APF tune without the extra Smaart delay adjustments won me over. The lesson for me was not that Smaart is not useful, but that a better-looking phase trace alone is not always equivalent to a better-sounding system. Driver locations, path-length differences, crossover choices, cabin gain, glass reflections, dash reflections, door reflections, the overall complexity of a vehicle interior, and the experience of a manual tuner can all affect what finally reaches the listener. Smaart is an extremely powerful tool for understanding and verifying those relationships, but the final decision still has to take into account the complete measured response and the listening result.


Listening
Listening to music in my truck is quite different from listening in my dedicated room at home. In my room, I am seated dead center between the speakers. In my truck, I am physically left of center, even though the tuning is trying to create a centered image from the driver’s seat. I’m not even sure how I ever became accustomed to listening this way. Nothing in a vehicle will replace, or even come remotely close to, the quality of what I hear in my dedicated room because it is not physically possible. Still, just as I enjoy listening with headphones, I also enjoy listening in my truck. Yes… all very different, yet still enjoyable.

The miniDSP has definitely helped improve several of my vehicle systems over the years. I believe this is my fifth C-DSP unit since giving up my JBL MS-8 processor. I know there are professional tuners who can do a fabulous job without Dirac Live, and I certainly do not mean to imply otherwise. I simply prefer what Dirac Live brings to the table in my own systems. In my experience, it has helped produce a cleaner, tighter, and more enjoyable result than I have been able to achieve without it.

I suspect quite a few car audio enthusiasts know of Steve Cook, former owner of Audio X in Florence, Alabama. Steve is the 2009 MECA World Champion for the Modex class. He won the 2009 World Finals Soundfest "SQ Best of Show." He is also the 2010 Alabama Champion in Sound Quality League Modex SQ. He has competed in SPL contests for quite a number of years and lays claim as a World Champ in dB Drag Racing, IASCA, and USACi. He is the only World Cup winner who is also an SQL World Champ. Simply put… he has serious credentials.

Steve installed a stellar system in my wife’s Lexus, and it was, without a doubt, the best vehicle system we had ever heard at that time. He nailed the tuning. A lot of my audio friends heard that vehicle and were amazed. When my wife purchased a new Lexus in 2020, I did not know much about the Zapco DSP Steve had installed in her previous Lexus, but I already had experience with the miniDSP C-DSP and decided to give it a go. I reused the same amps and sub but replaced the front-stage speakers and DSP. The system with the miniDSP sounds better to us. Granted, that comparison is not entirely fair to Steve because 6-7 years had passed between his installation and mine. It is very possible he could have done just as good a job, or better, with newer technology had he installed it at the same time I installed the miniDSP with Dirac Live. Nonetheless, that is the closest direct comparison I have had in a similar vehicle.

The miniDSP is an excellent DSP, and I do not think I would want to be without it in a custom build. Yes, I use it in conjunction with my Helix Ultra S, and I do not believe my current system would sound nearly as good if either unit were removed. I need both to accomplish what I want. However, the miniDSP C-DSP is what brings Dirac Live into the system, and that is a big part of the magic for me. I will not try to describe the sound too much because that gets subjective in a hurry. There is no way it will ever sound as good as my dedicated room system… yet it seems a bit ironic that I enjoy it almost as much.

Below are some tracks I frequently use to check bass behavior, staging, dynamics, and overall system balance. The noted frequencies are not meant to be laboratory measurements... just simple REW measurements, and are practical listening references that have been useful in my truck.
  • Til Tomorrow – Yello / Till Brönner (50 Hz): Smooth, controlled bass line with excellent trumpet texture and a spacious, polished Yello-style soundstage.
  • Alive – oblyx (40 Hz): Clean electronic bass pulse with good weight and drive; useful for checking punch without excessive boom.
  • Turner’s Ship – Malia / Boris Blank (20 Hz): Deep, atmospheric track with visceral low bass, layered textures, and a large, cohesive soundfield.
  • Stay – Yello (low 20 Hz range up to 60 Hz): Excellent low-end extension test with Yello’s typical deep bass layering and wide electronic staging.
  • Get On – Yello (mid-20 Hz to 60 Hz): Strong rhythmic bass energy with clean electronic punch; good for checking sub-to-midbass control.
  • Bass I Love You Too – Bassotronics (15 Hz and 30 Hz): Pure low-frequency torture test; useful for checking true sub-bass output, excursion limits, and cabin rattles.
  • Colors (Pt. 2) – Halsey (20 Hz): Dreamy, atmospheric instrumental-style track with deep underlying bass and a floating, spacious presentation.
  • House of the Rising Sun – Hanne Boel (30 Hz up to 60 Hz): Rich vocal presence with strong low-end support; good for checking bass weight without overwhelming the vocal.
  • Uninvited – Alanis Morissette (20 Hz and up): Excellent broad frontstage and orchestral swell; great for checking dynamics, vocal focus, and stage width.
  • Queen Mary – Francine Thirteen (30 Hz): Dark, dramatic, bass-heavy track with strong left/right effects and a haunting vocal presentation.

Final Thoughts
The miniDSP C-DSP 8x12 DL is not a perfect processor, but it remains one of the most impressive car-audio DSP products I have used. Its strength is not that it makes tuning effortless. It does not. Its strength is that it gives the user tremendous control and Dirac Live correction in a package that remains reasonably priced compared with many high-end car-audio processors. This is not the processor I would recommend to someone who wants a quick, simple, plug-and-play installation. There is too much to understand: routing, mixer assignments, Dirac channel configuration, bass management, PEQ, crossovers, all-pass filters, target curves, measurement technique, and configuration management.

The C-DSP rewards patience and careful setup. When the processor is properly configured and the system is measured carefully, the results can be "spaceship" excellent. Dirac Live is the main reason this unit continues to stand out for me. There is no doubt that traditional DSP tuning can produce outstanding results in the right hands, but Dirac adds another layer of correction that is difficult to replicate manually, especially at lower frequencies and around crossover regions. In my experience, it helps the system sound tighter, cleaner, more controlled, and better integrated. The C-DSP 8x12 DL also offers useful flexibility within its Dirac-based workflow. I can use separate pre-Dirac and post-Dirac configurations, adjust house-curve filters, and reload known-good settings without rebuilding the setup each time. Other high-end processors may offer more routing options, more outputs, more PEQ capacity, or a more modern interface, but the C-DSP still gives me a workable path to use Dirac Live in a custom car-audio system.

Its main limitations are also clear. Eight Dirac-calibrated outputs can become restrictive in a fully active system with subwoofers, midbass drivers, midrange drivers, tweeters, and rear fill. Ten PEQ filters per channel may be enough for many users, but more complex systems can run out quickly, especially when using filters for both pre-Dirac cleanup and post-Dirac voicing. The software plug-in is sufficient, but it is not the most modern or intuitive interface. It gets the job done, but it assumes the user knows what they are trying to accomplish. For my own system, the C-DSP 8x12 DL is still worth the effort. Even with the Helix Ultra S handling additional processing duties, the miniDSP remains the heart of the calibration process. The Helix gives me additional routing, rear-fill processing, and PEQ flexibility, while the miniDSP provides the Dirac Live correction layer I prefer.

I hope the setup portion of this Review and Setup/Tuning Guide remains useful beyond the first read. Even after becoming familiar with the C-DSP workflow, there are still times when it helps to jump back to a specific section and confirm a setting, sequence, or method before making changes. That is part of why I wanted the guide to be detailed and easy to navigate.

Bottom line: the C-DSP 8x12 DL is a serious processor for users who are willing to measure, experiment, and learn the workflow. It is not the easiest DSP to use, but it is extremely capable and gets easier with each use. For an advanced active car audio system where Dirac Live correction is a priority, it remains one of the most compelling options.

Highly Recommended!

Please report errors or broken links... thanks!
 
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