Anybody else using a distributed array sub system?


     I was just about to respond to zardozmike's forum post titled 'subwoofers' about suggestions for subs for Magnepan MGIII speakers but decided a new post might be more useful for him and others.  I have Magnepan 2.7QR speakers and posted a similar question about a year ago.  After reading his thread, I realized he was getting about the same responses I had received.  All were very good responses but I thought a new thread detailing my effective solution may be more relevant and attract responses from other users of a distributed array sub system.    


     About a year ago I purchased the Audio Kinesis DEBRA (Distributed-Eq Bass Reflex Array) sub system from James Romeyn Music and Audio in Utah. Here's a link describing the system:


http://jamesromeyn.com/old-pages/home-audio-gear/dsa-1-0-distributed-subwoofer-array-5-pieces-4k-usd...

 

       This system is expensive at $2,990 but well worth the investment.  I rationalized the price by noting it's about the same as a pair of very good regular subs.


     The performance of this system in my 23' x 14' living room is excellent.  The bass can be fast, tight and tuneful for music or loud and impactful for music and home theater.  The subs seem to disappear since there are no audible clues to their locations; the bass is very well integrated into the music and movies. From my personal experience, I'm not convinced of the reality of stereo bass but was willing to give it a try.    I was originally thinking of buying 2 high quality subs such as Rhythmik, SVS, JL, Martin/Logan, Vandersteen or REL.  I was skeptical of the DEBRA system at first but, after reading a lot of research about multiple sub systems on the internet, I decided to give it a try and I'm now very thankful that I did. 


     Because it is such an ideal system for me, and because I think it would work well in almost any room or system, I want to go into more detail about the system, its setup and the theory behind it. I have no affiliation with the company but will admit, after considerable phone and email time with the dealer, that I now consider James Romeyn a friend of mine but don't know if he feels likewise.

     The system consists of the following:

A dedicated Dayton Audio mono class A/B amp rated at 950 watts @ 4 ohms with dual A&B spkr output terminals.

4 67lb. bass-reflex  subs that measure a relatively small 23.75" H x 14.5" W x 10.375" D.

Each sub is ported on the bottom, supported by 3 spiked cones and contains a single 10" 4 ohm driver. The subs are designed to be facing, and within 2" of, the room walls.

     The setup procedure is:

Sub#1 is hooked up and placed on its back  (driver facing the ceiling) at the normal listening position.  Music is played that has good and repetitive bass.

Walk around the edges of the room and determine exactly where the bass sounds best to you.

Attach the 3 spiked footers to Sub#1 and position it upright facing the nearest wall to the spot you determined the bass sounded best.

Sub#2 is hooked up and placed on its back at the primary listening position. With sub 1 & 2 playing, continue walking around the edges of your room and determine again where the bass sounds best to you.

Attach the 3 spiked footers to Sub#2 and position it upright facing the nearest wall to the spot you determined the bass sounded best.

Repeat this procedure for sub 3 & 4.

Small positioning adjustments may need to be made for each sub due to avoiding furniture and the WAF. 

Once completed, final sub hook up is done in parallel:

Attach a single wire from the amp's speaker A's pos. output terminal and to Sub#1's pos. input terminal.

Attach a single wire from the amp's speaker A's neg. output terminal and to Sub#2's neg. input terminal.

Attach a single wire from Sub#1's neg. input terminal to Sub#2's pos. input terminal.

Attach Sub 3 & 4 using this parallel method on the amp's speaker B's output terminals.

I ordered single, high quality and low gauge speaker wire along with the sub system for a very reasonable price. Once the ideal locations for the subs was determined, I drilled holes in my room's floor to the crawl space below, and was able to hide the connecting wires. 

     I'm definitely not an expert on subs or room acoustics but, from my reading, here is how I understand the theory behind the distributed array sub systems:


The lower the frequency the longer the sound wave produced, or launched,  into a room. 

Since these waves can be even longer than the actual dimensions in many rooms, these low frequency waves bounce off room surfaces and the music may dictate subsequent bass waves being launched into this acoustic environment. These initial waves, their reflections and subsequent bass waves inevitably collide and cause 'standing waves'.

Areas in the room where sound waves meet can make the bass sound under emphasized, over emphasized or even totally missing (nulls caused by wave cancelation).

When one sub is launching low frequency waves from 1 specific location, areas in a specific room where bass response is not accurate will be numerous and predictable based on sub location and room dimensions.

Adding a 2nd sub to the room will decrease standing waves and increase bass accuracy and bass dispersion.

According to scientific studies I read, standing waves are reduced, and bass accuracy and dispersion increased, as more subs are used in a given room.  Their experiments utilized more subs than anyone would even consider for home use. They basically concluded that the more subs in a room, the fewer standing waves are perceived and the better the bass quality and bass dispersion results.

However, they determined that most of the benefits are gained with the use of 4 subs, with only minimal and incremental gains in performance attained through additional subs.  Due to practical room considerations, the researchers recommended 4 subs for an effective distributed array bass system.


     So that's the equipment, set-up and the theory behind the DEBRA system and I can personally attest to its effectiveness in my room.  I have 6 listening/viewing positions in my combination music and ht system in my living room.  Bass response is equally good at all 6 positions without the use of acoustic devices (no absorbing or diffusing panels or bass traps) and without any electronic  equalization (room analysis/correction equipment, software or eq).  I should mention I've never had my system/room analyzed using a mike and software.  From my purely subjective perspective, however, I'm confident the results would be good since I spent hours on the setup and critical listening from all six listening positions in my room.  I would suggest this type of sub system as a viable alternative for anyone considering investing in one or more quality subs.  The system is rated clean at 113 decibels at 20 hz.  I've often heard and felt it go much lower.  It feels and sounds clean and right but I can't verify the decibels or lack of distortion.


Sorry this turned out so long and windy,

  Tim

Also, my system photos are old but I'll try to update them showing my current system (with the subs and new electronics) soon.



     


  

128x128noble100
wolf garcia,

     I'm definitely not an expert on bass systems or acoustics but I have a few thoughts on your situation based only on personal experience and sub research:

1. I think your outdoor deck setup may work well since there are no standing waves created on your deck since there are no room boundaries that create them.  You're listening likely to only the direct sound waves from both your speakers and sub.

2. Your indoor setup may not work as well because there are standing waves created in your listening room since there are room boundaries that create them.  

I suggest you try the following to see if it improves the sound in your in-doors listening system:

Place your Q150 sub at your normal listening position and play some music with good and repetitive bass at a medium volume.

Starting near the front right corner of your room, walk around the perimeter of your room completely and determine exactly where the bass sounds best to you.  For best results, you may need to crouch down to approximate your ear height when seated at your normal listening position.

Move your Q150 to the spot you determined the bass sounded the best to you.

 Place your Q108 at your normal listening position.and continue playing the music with repetitive bass

Starting  at the newly sited Q150, continue walking the perimeter of the room and determine again where the bass sounds best to you.

Move the Q108 to the spot the bass sounded best to you.

Done.  

 I think the above process will allow for the best bass in your room  using both your subs.  I think it'll reduce standing waves (bass peaks and nulls) and give you good, smooth bass response at your normal listening position and possibly throughout most of your room.

Hope this helps,
 Tim
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Harumph! (heh) I actually AM an expert in bass and acoustics (pro musician and live sound mixer for 5 decades or so), although my opinions on sound aren't necessarily driven by anything beyond personal taste. I wasn't complaining about my indoor setup, just describing it. There are no standing waves at the sweet spot I listen from as I set up the first (Q150e) REL carefully initially…I also highly recommend spending the time to do that. Bass intensity is of course more powerful in the corners (normal), and I was merely noting the fact that REL #2 does mitigate the standing waves near it by providing an in phase sound wave to eat the bass that crawls along to the corner it's near. I think that's why "swarm" subs are a great idea and work so well. A note on my outdoor sound…the little 8" woofer in the Q108 II when locked into its spot (the window and a rubber foot hold it in place) does use the rest of the window and outside walls to provide an interesting gigantic baffle…the design of this speaker is floor firing normally, but firing out to the deck works really well when combined with the coincident tweeted KEFs also stuck in the windows for deck duty. Plus I think the plants like my choice of music…I could be imagining that…jazz plants…
I'm using Duke's Swarm system with five subwoofers and two Vandersteen Quatro Woods which have built in subs of their own.  In my previous set-up I used a single Vandersteen V2W sub with the Quatros.  I use a Meridian G68XXD with MRC room correction below 250 hz.  The previous system required 16 filters between the Vandersteen speakers, the V2W sub and the Vandersteen center and surround speakers (ITU spec. 5.1 set-up).  The Swarm setup required only 2 filters, and only for the two Vandersteen surround speakers (VSM-1s), which are close to the rear ceiling / wall corners.  The room, wherever you set the calibration mic, is very flat and uniform.  

The sound, particularly with large-scale symphony music, is utterly realistic, with the acoustics of the hall the recording comes from.  (I regularly attend the St. Louis Symphony Orchestra classical series, so I know what it should sound like.). My previous set-up (single sub) sounded like a very good hi-fi system in my medium size room.

Anyone who dismisses these multi-sub systems doesn't understand the acoustics of small rooms, and is really missing something special.  As added bonus, the power response of the swarm and similar systems is uncanny.  You really haven't heard "bass slam" until you experience one of thes set-ups.

Noble100 wrote:
johnnyb53,

    Yes, the Magnepans do have an advantage over box spkrs in terms of quality of bass. I have much older 2,7 Magnepans than you but, when I switched amps fro an older Aragon class A/B amp (200 watts@4ohms) to a new pair of class D monoblock amps (1,200 watts @4ohms), I was quite impressed with the amount and quality of the bass produced.
I didn't mention it in this thread before, but actually I also have a pair of small subwoofers to add some depth and slam to the Maggie 1.7s. The self-canceling nature of the 1.7s minimizes the upper bass hump that's so pervasive in room matching, and why many audiophiles have bass traps. 

Another advantage, however, is that it also makes it *easier* to match  subs with Maggies. I have a pair of Mirage MM8s. These now-discontinued mini-subs were little gems--long-throw 8" drivers with twin passive radiators. The active driver occupied the entire sub enclosure except for the plate amp, which packed 1400 watts peak (340 rms) power. Controls were granular--continuous knobs for crossover (50-200 Hz), phase (0-180deg.) and volume. 

To dial in the phase, I put on "With a Little Help from My Friends" from the recent Beatles Mono reissue. I know the bass line from this song note for note and it dances frequently across that 50Hz crossover line. I played it one channel at a time and twisted the phase knob until it sounded right. Then I did the same thing with the other channel. At that point I had excellent-to-perfect (sounds perfect to me) integration between Maggie panels and subwoofers. 

You might say I dialed in perfect subwoofer integration with "A Little Help from My Friends."



wolf garcia,

 My mistake, I thought you were looking for assistance.  With your experience, I now realize you don't need it.

Tim