2 Subwoofers combined in miniDSP alignment with mains

[Baku]

I need an advice for the my stereo setup.
I am using a 7.2.4 system that is used for HC and music in a dedicated room. Rough dimensions : 540 cm x 330 cm. Ceiling 260 cm.

The stereo path of my system :
DAC: Denafrips ARES 12TH
Pre/Pro: Emotiva XMC-2
Power: Emotiva XPA-2
Speakers : KEF R3
Subwoofers : 2 x SVS SB-2000 Pro combined with MiniDSP 2x4HD
HTPC with local lossless collection streamed to the DAC exclusively through JRiver with USB connection.

PC with Jriver -> usb to DAC -> balanced to XMC-2 as a pre Amp with bass management -> bass goes to miniDSP with mono single unbalanced connection (both subwoofers connected to miniDSP) - stereo balanced to XPA-2 amp with R3 connected.

Since XMC-2 has several slots for speakers setup, this way I manage the easiest transition between music and HC when needed with a push of a button. Considering every setup is configured properly.
In the past I was using the automatic room correction for both the music and the HC with some tweaks here and there. Audyssey (Denon), ARC (Anthem) and Dirac since Emotiva XMC-1.
I have some knowledge and experience with REW over the years and the calibrated Umik-1 mic I have purchased in the past from the Cross Spectrum. So now I would like to try the manual path for the stereo path.
The MLP for the music is a static single position ( focused ).
The subs are located in opposite side of the room. One is in front of the MLP on the plane of the mains - front short wall - about 1/4 room width, and the second is about middle back wall. Considering the room response this gives the best result on the MLP area.
The subs are aligned between each other in order to maximize the MLP frequency response with 16ms delay for the back wall sub in the miniDSP as simulated inside the REW with the alignment tool.

For a couple of days now I am, trying to align the combined subwoofers response with the mains - but can't figure out what is it exactly I am aiming for and how to address the time domain properly. I got used that Dirac manages the phase issues and now after about 20 hours of reading the theoretical papers, posts on different boards, watching youtube, then trying and getting lost again again and again I was thinking to forget about the manual path, to kick in Dirac live and get back to the music enjoyment I am missing... Nevertheless I am enjoying the learning curve and maybe with some help I'll progress sooner.
I understand that the IR is not the tool for the bass alignment. Phase alignment is the way to go. But how exactly ?
I saw many suggestions from simply using the REW time alignment tool to more complex ones but nothing I tried brought the result to the the aligned step/phase/ir. Focusing on one taking the result far from another and vice versa. Remeasuring with the delays applied after the REW simulation brings wrong results in the time domain. Maybe this does not work for my case because I have aligned 2 subs with a quite big delay between each other and now trying to align 1 virtual sub makes all the calculation predictions to collapse. But on the other hand what is the difference in terms of the response and the time domain ? The phase is the phase is the phase. Maybe I am mistaken...
What are the preferred tool(s?), order, goal, verification method... As far as my knowledge goes it should be approximately:

• Measure 1, 2, 3...
• Calculate 1, 2, 3...
• Apply x' delay

** Remeasure, recalculate, apply y' delay probably
...
My toolbox is full, but I feel empty handed...
Please advice.

 

[John Mulcahy]

I understand that the IR is not the tool for the bass alignment. Phase alignment is the way to go. But how exactly ?
I saw many suggestions from simply using the REW time alignment tool to more complex ones but nothing I tried brought the result to the the aligned step/phase/ir. Focusing on one taking the result far from another and vice versa. Remeasuring with the delays applied after the REW simulation brings wrong results in the time domain.

What is it you consider wrong about the time domain result? The aim of the alignment is to have a good transition from subs to mains, which is achieved by having their phases aligned around the crossover frequency. A good alignment will avoid dips in the response through the crossover region. You can do that using the alignment tool for phase alignment or, if using the 5.20.14 early access build, filtered impulse response alignment. Either should give much the same result. What you won't get from alignment is phase correction of the combined IR, which I'd guess is what you may be looking for. You need Dirac (easy) or a separate manual process (hard ) to achieve that.

 

[AudiocRaver]

Maybe this does not work for my case because I have aligned 2 subs with a quite big delay between each other and now trying to align 1 virtual sub makes all the calculation predictions to collapse

I believe that to be your problem.

Here is an approach that would work really well in your situation. Place both of your subwoofers against the front wall, one directly behind each of your two front Main bookshelves. Think of each of the subwoofers as the low frequency part of the front Main that it is lined up with. You won't even need to tie the subs together like everyone usually says you must.

You will want to pull your front Mains out away from the front wall in order to achieve the best soundstage and imaging (SS&I) anyway. Pull them out far enough so the boundary reflection cancellation frequency falls into the frequency range that the subwoofer will be handling, and put the subwoofers close enough to the wall so their boundary reflection cancellation will fall into the frequency range that the mains are handling. Then use your miniDSP 2x4 to create 48 db/octave crossovers right in between those two frequencies, around 120 Hz is a good first try. That sounds high to run a sub, but if you don’t tie the two together, there are no localization problems.

Let Dirac Live flatten everything out and calculate the delays for you. The REW phase and frequency response plots (with Dirac applied) will help you find the right frequency for the crossover. The left-right room symmetry makes it a lot easier.

I have my subs facing the front wall for some room gain for the Dirac Live filters to work against to really flatten out the low frequency response. Then the two subs can work together beautifully as a stereo pair of woofers. With a little care, you can get a smooth response at the crossover and everywhere else, including near perfect L/R phase alignment from 20 Hz to above 10 kHz.

If you are interested in giving it a try, we can get into some of the math. Let me know.

----

By the way, plan on tons of absorption, it will help dampen the LF range and will improve image clarity.

 

[deercreekaudio]

I need an advice for the my stereo setup.
I am using a 7.2.4 system that is used for HC and music in a dedicated room. Rough dimensions : 540 cm x 330 cm. Ceiling 260 cm.

The stereo path of my system :
DAC: Denafrips ARES 12TH
Pre/Pro: Emotiva XMC-2
Power: Emotiva XPA-2
Speakers : KEF R3
Subwoofers : 2 x SVS SB-2000 Pro combined with MiniDSP 2x4HD
HTPC with local lossless collection streamed to the DAC exclusively through JRiver with USB connection.

PC with Jriver -> usb to DAC -> balanced to XMC-2 as a pre Amp with bass management -> bass goes to miniDSP with mono single unbalanced connection (both subwoofers connected to miniDSP) - stereo balanced to XPA-2 amp with R3 connected.

Since XMC-2 has several slots for speakers setup, this way I manage the easiest transition between music and HC when needed with a push of a button. Considering every setup is configured properly.
In the past I was using the automatic room correction for both the music and the HC with some tweaks here and there. Audyssey (Denon), ARC (Anthem) and Dirac since Emotiva XMC-1.
I have some knowledge and experience with REW over the years and the calibrated Umik-1 mic I have purchased in the past from the Cross Spectrum. So now I would like to try the manual path for the stereo path.
The MLP for the music is a static single position ( focused ).
The subs are located in opposite side of the room. One is in front of the MLP on the plane of the mains - front short wall - about 1/4 room width, and the second is about middle back wall. Considering the room response this gives the best result on the MLP area.
The subs are aligned between each other in order to maximize the MLP frequency response with 16ms delay for the back wall sub in the miniDSP as simulated inside the REW with the alignment tool.

For a couple of days now I am, trying to align the combined subwoofers response with the mains - but can't figure out what is it exactly I am aiming for and how to address the time domain properly. I got used that Dirac manages the phase issues and now after about 20 hours of reading the theoretical papers, posts on different boards, watching youtube, then trying and getting lost again again and again I was thinking to forget about the manual path, to kick in Dirac live and get back to the music enjoyment I am missing... Nevertheless I am enjoying the learning curve and maybe with some help I'll progress sooner.
I understand that the IR is not the tool for the bass alignment. Phase alignment is the way to go. But how exactly ?
I saw many suggestions from simply using the REW time alignment tool to more complex ones but nothing I tried brought the result to the the aligned step/phase/ir. Focusing on one taking the result far from another and vice versa. Remeasuring with the delays applied after the REW simulation brings wrong results in the time domain. Maybe this does not work for my case because I have aligned 2 subs with a quite big delay between each other and now trying to align 1 virtual sub makes all the calculation predictions to collapse. But on the other hand what is the difference in terms of the response and the time domain ? The phase is the phase is the phase. Maybe I am mistaken...
What are the preferred tool(s?), order, goal, verification method... As far as my knowledge goes it should be approximately:

• Measure 1, 2, 3...
• Calculate 1, 2, 3...
• Apply x' delay

** Remeasure, recalculate, apply y' delay probably
...
My toolbox is full, but I feel empty handed...
Please advice.

Electronic Delay Measurement Method​

Using REW to electronically calibrate delays is the most accurate method for ensuring the acoustic wavefronts of all speakers are coincident to the listening area. These delays should be calculated prior to running an REW or Dirac Live room correction project. Having delay settings in place will provide better results for your room correction project. As you proceed, be sure to check your work and verify it with physical measurements. Keep in mind that sound travels at 1.11 feet per millisecond.

Typical Measurement Layout

The diagram below depicts the physical layout and center listening position for making typical measurements. This example is for a 2.2 stereo system setup.

Diagram 4. Typical layout for electronically measuring delays in a 2.2 stereo system

Crossover and Equalizer Settings

Electronic delay measurements will be performed with all crossover and equalizer settings set to off or bypass. This ensures the most accurate delay measurements. Be sure to save your XML configuration files prior to bypassing and removing the crossover settings. Once you have completed all measurements and are satisfied with your delay settings, you can reinstall your basic Device Console XML configurations.

Diagram 5. All crossovers bypassed or turned off in Device Console

Acoustic Timing Reference Signal

An acoustic timing reference signal allows you to electronically measure the relative delays between the four speakers in a 2.2 system. The first step is to determine which of the speakers is closest to the listening area. Keep in mind that speakers with additional digital signal processing, such as subwoofers with DSP or wireless interfaces, can have significantly greater delay.

It's required that the test signals have sufficient bandwidth, preferably at least 250 Hz. In order to achieve this you need to turn off all crossovers or ensure they are set to their maximum frequency. The greater frequency range you can get out of the subwoofers, the more accurate the measurements.

Setting REW Preferences

On the REW preferences page, set the timing reference output to the left channel and set the speaker output (delay measurement signal) to the right channel. This corresponds to channels one (1) and two (2) on Device Console.

Diagram 6. The REW Preferences Soundcard tab showing timing reference signal on the left channel (1) and delay measurement signal on the right channel (2)

Measurement Reality Check

Before making actual delay measurements from the listening position, start out with the microphone near the acoustic timing reference output, in this case the left main speaker. Next, make measurements of all the other speakers and subwoofers in the system that are farther from this point. You should be able to confirm with a tape measure that your electronic measurements are true (sound travels at 1.11 feet per millisecond).

Electronic Delay Measurement Workflow

1. Verify the presence of the timing reference signal
2. Place the microphone in the center listening position
3. Measure each speaker / subwoofer delay relative to the timing reference source
4. Calculate the delay settings for Device Console
5. Enter the required additional delays into the Device Console delay row
6. Verify your delay corrections

Speaker Delay Measurement Selection

With the mute and routing matrix functions of Device Console, you can select which speaker / subwoofer is being measured for delay. In this first example, the leftmost main speaker (our acoustic timing reference) is generating both the timing reference signal on the left channel and the delay measurement signal on the right channel. The expectation is for this number to be close to zero, as the signals are coincident.

In the first measurement below, Device Console shows the timing reference signal and delay measurement signal coming from the left main speaker.

Diagram 7. Measuring delay on the same speaker that is generating the timing reference signal

In the second measurement below, Device Console shows the timing reference signal coming from the left main speaker and the delay measurement signal coming from the right main speaker.

Diagram 8. Measuring the delay of the right main speaker relative to the left main speaker (timing reference)


Once you have completed the delay measurements of the remaining speakers and subwoofers, the resulting REW display will have all of the delays listed on the left.

Diagram 9. Delay measurements of all speakers shown together, with the individual delay values on the left (see Diagram 10 for close up)

Diagram 10. Close up of REW delay readout

Calculating Delay Settings for Device Console

Once all your delay measurements are complete, transfer them from the REW page into a spreadsheet. You can then determine which speaker / subwoofer is the farthest away (physically and electronically) by identifying the largest delay value (right subwoofer in our example). In your spreadsheet subtract the largest delay value (6.1 ms) from all of the other delay measurements. See last row of spreadsheet below.

Diagram 11. Electronic delay measurement calculation spreadsheet

After completing your calculations, the resulting delay figures will be added as positive numbers in the Device Console delay settings row, highlighted in red below.

Diagram 12. Delay values are entered into Device Console

Verify your Delay Corrections

You should now have time aligned all of the speakers and subwoofers in your system to the center listening area. You can verify this by going through and repeating all of the delay measurements. You should expect to see variances of a few milliseconds or less.


Next Steps

Now that you have inserted your delay measurements in Device Console, you will complete or reinstall your crossover and relative level settings. It’s now time to move on to either your REW or Dirac Live room correction project.

Please see our Tech Blogs which can apply to this situation

Deer Creek Audio is an authorized miniDSP dealer.

 

[Sonnie]

Wayne has a great suggestion to try. I have 6 SVS subs in my room. I use 4 SB16's for music with two in the front near the mains and two in the rear. Then for movies the PB16's kick in. I use REW to time align the subs with no issues whatsoever. Wayne has heard my system and can confirm.

 

[AudiocRaver]

No kidding, Sonnie's system is absolutely killer (in the good way).

The approach I suggested might sound outlandish, but the main ideas were reverse engineered from published works by Carl Tatz, who sets up mastering and mixing rooms in Nashville following that method, which he developed.