More
- Preamp, Processor or Receiver
- Onkyo TX-SR705 Receiver
- Main Amp
- Crown XLS 1502 DriveCore-2 (x2 as monoblock)
- Additional Amp
- Behringer A500 Reference Power Amplifier
- Front Speakers
- MartinLogan Electromotion ESL Electrostatic (x2)
- Center Channel Speaker
- Phantom Center
- Surround Speakers
- NSM Audio Model 5 2-Way (x2)
- Subwoofers
- JBL ES150P Powered Subwoofer (x2)
This post was inspired by my dealings with a number of different listening room challenges, starting with the setup of the LXmini speakers which I built, reviewed, and now own. They can deliver bass down to 50 Hz, but not with much volume. Even while finishing the build process, I was figuring out how to give them an effective boost in volume by using stereo subwoofers. Why use stereo subs? The limiting factor for volume from the LXmini is the amount of DSP boost the LF driver receives to achieve flat response, a 6 dB/oct boost that rises from 120 Hz as the frequency decreases to 50 Hz. Solving the problem without messing up the LXmini’s pinpoint imaging would mean running two subs, one located next to each LXmini, handling the spectrum below 120 Hz, but doing so would not allow the two subs to be run together from a single channel as is commonly recommended for multiple subwoofers in a system.
We are shown from Schroeder’s acoustical research that the average listening room is primarily a modal environment below 200 Hz, and are oft forgetful of the exceptions and complications to be dealt with in that modal region. Non-modal LF reflections can mess with frequency response, for one thing (sometimes called Speaker Boundary Interference Response, or SBIR, although any strong early reflection can cause problems), and the range from 80 Hz on up can be localized by our hearing and must be handled with SS&I goodness in mind, for another.
When I first built the LXmini pair, I ended up with a hacked-together version of the more refined solution described in this article, a Dual Band Bass Management (DBBM) approach which solves the localization issues with a single pair of subs, allows Dirac Live to work with the DDRC-88BM’s bass management features, and allows the 88BM to pitch in with delay and pre-EQ (before calibrating and activating Dirac Live room correction) on a per-sub basis where needed.
The DBBM approach is not likely to find its way into use for many applications because applications with full-range speakers will not benefit from it, and for those that do benefit, the improvement is subtle. But for those who are obsessively perfectionistic about soundstage and imaging (SS&I) for their 2-channel listening, the foundation of imaging starts with the lowest tones localizable, around 80 Hz. A small point-source two-way speaker, for instance, can be unbeatable for imaging, but might have a low end that needs some boost above 80 Hz. This DBBM approach can help provide that boost while preserving the fine details of SS&I in that application.
Enter The miniDSP DDRC-88BM
The DDRC-88BM is a virtual audio Swiss army knife when it comes to taming the performance of a two-channel or surround system, with its 8 channels of Dirac Live, analog inputs and outputs, complete bass management, per-channel delay, EQ, and crossover controls. Although this article will focus on the Dual-Band Bass Management concept, those capabilities naturally overlap and synergize, so I will cover them as well, albeit briefly. After all, a system that has great bass but lousy SS&I will still be considered a lousy sounding system by most.
The DDRC-88BM can aid with the following common speaker setup issues:
The Modal Room
Below about 200 Hz, a room’s modal character makes it important to measure the delay/eq results of multiple subs together, since they tend to work as a single acoustical energizing unit for the room in that frequency range. I have watched subwoofer experts like Mark Seaton and Sonnie Parker fiddle with individual sub delays and EQs, then measure the conglomerate result, then fiddle and measure some more, a bit lost as to how they end up making a big dip or peak in the bass response disappear through a process they have obviously practiced many times and learned to apply intuitively.
It makes perfect sense to tie multiple subs together below 80 Hz, since the wavelengths in question are far too long for the ear to localize. But between 80 Hz and 200 Hz, sounds become more and more easily localized. And while it is true that our psycho-acoustical brains are quite adept at integrating the harmonics of a sound with its fundamental bass tone to present us with a decent image, decent imaging becomes great imaging when a sound’s components are delivered pre-aligned in the acoustical realm. “Other-worldly,” “I got chills,” “it messes with your head,” “Carved in space,” are image descriptions that I have heard. Subtle differences, but the kind that can contribute to a transformative listening experience.
LXmini Results
I started out working with the LXmini for proof of concept because they were the speakers that drove the development of this idea.
LXmini frequency response with no Dirac correction, no DBBM.
LXmini Impulse response showing time alignment at the LP.
LXmini frequency response with Dirac Live but no DBBM.
LXmini frequency response with DBBM. The audible difference does not show up in such plots, but can be heard with the right program material.
Here the contributions from the different parts of the DDRC-88BM are shown. The lowest band, below 60 Hz, is mono. The stereo band, from 60 Hz to 120 Hz, is muted for two measurements in this plot so it can be easily seen.
Implementation details will be added shortly,
LXmini speakers courtesy of Madisound and Linkwitz Labs
DDRC-88BM courtesy of miniDSP
NOTE: This thread will be completed in stages, since there will be several speakers involved in the testing and evaluation. As more information is added, I will amend this first post and then post a new entry indicating the amendment.
We are shown from Schroeder’s acoustical research that the average listening room is primarily a modal environment below 200 Hz, and are oft forgetful of the exceptions and complications to be dealt with in that modal region. Non-modal LF reflections can mess with frequency response, for one thing (sometimes called Speaker Boundary Interference Response, or SBIR, although any strong early reflection can cause problems), and the range from 80 Hz on up can be localized by our hearing and must be handled with SS&I goodness in mind, for another.
When I first built the LXmini pair, I ended up with a hacked-together version of the more refined solution described in this article, a Dual Band Bass Management (DBBM) approach which solves the localization issues with a single pair of subs, allows Dirac Live to work with the DDRC-88BM’s bass management features, and allows the 88BM to pitch in with delay and pre-EQ (before calibrating and activating Dirac Live room correction) on a per-sub basis where needed.
The DBBM approach is not likely to find its way into use for many applications because applications with full-range speakers will not benefit from it, and for those that do benefit, the improvement is subtle. But for those who are obsessively perfectionistic about soundstage and imaging (SS&I) for their 2-channel listening, the foundation of imaging starts with the lowest tones localizable, around 80 Hz. A small point-source two-way speaker, for instance, can be unbeatable for imaging, but might have a low end that needs some boost above 80 Hz. This DBBM approach can help provide that boost while preserving the fine details of SS&I in that application.
Enter The miniDSP DDRC-88BM
The DDRC-88BM is a virtual audio Swiss army knife when it comes to taming the performance of a two-channel or surround system, with its 8 channels of Dirac Live, analog inputs and outputs, complete bass management, per-channel delay, EQ, and crossover controls. Although this article will focus on the Dual-Band Bass Management concept, those capabilities naturally overlap and synergize, so I will cover them as well, albeit briefly. After all, a system that has great bass but lousy SS&I will still be considered a lousy sounding system by most.
The DDRC-88BM can aid with the following common speaker setup issues:
- Image clarity is improved with small speakers through accurate bass tone localiation.
- More placement options become available with multiple subwoofers, for the user who is struggling with room modes or SBIR reflection/cancellation issues.
- Each subwoofer’s signal can be given custom delay and EQ treatment as needed for further evening out of combined sub frequency response.
- Dirac Live room correction provides the final SS&I polish.
The Modal Room
Below about 200 Hz, a room’s modal character makes it important to measure the delay/eq results of multiple subs together, since they tend to work as a single acoustical energizing unit for the room in that frequency range. I have watched subwoofer experts like Mark Seaton and Sonnie Parker fiddle with individual sub delays and EQs, then measure the conglomerate result, then fiddle and measure some more, a bit lost as to how they end up making a big dip or peak in the bass response disappear through a process they have obviously practiced many times and learned to apply intuitively.
It makes perfect sense to tie multiple subs together below 80 Hz, since the wavelengths in question are far too long for the ear to localize. But between 80 Hz and 200 Hz, sounds become more and more easily localized. And while it is true that our psycho-acoustical brains are quite adept at integrating the harmonics of a sound with its fundamental bass tone to present us with a decent image, decent imaging becomes great imaging when a sound’s components are delivered pre-aligned in the acoustical realm. “Other-worldly,” “I got chills,” “it messes with your head,” “Carved in space,” are image descriptions that I have heard. Subtle differences, but the kind that can contribute to a transformative listening experience.
LXmini Results
I started out working with the LXmini for proof of concept because they were the speakers that drove the development of this idea.
LXmini frequency response with no Dirac correction, no DBBM.
LXmini Impulse response showing time alignment at the LP.
LXmini frequency response with Dirac Live but no DBBM.
LXmini frequency response with DBBM. The audible difference does not show up in such plots, but can be heard with the right program material.
Here the contributions from the different parts of the DDRC-88BM are shown. The lowest band, below 60 Hz, is mono. The stereo band, from 60 Hz to 120 Hz, is muted for two measurements in this plot so it can be easily seen.
Implementation details will be added shortly,
LXmini speakers courtesy of Madisound and Linkwitz Labs
DDRC-88BM courtesy of miniDSP
NOTE: This thread will be completed in stages, since there will be several speakers involved in the testing and evaluation. As more information is added, I will amend this first post and then post a new entry indicating the amendment.
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