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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
noble100's avatar
noble100 OP
1,093 posts
 
pryso,

I'm not sure if you know, or have heard, how good Vandersteen speakers are.  The Quatro Woods that dcbingaman owns are one of their top models.  They are full-range speakers that are expensive (about $11k) and have been very well reviewed.  Here's a link to one of the reviews I've read:

 http://www.positive-feedback.com/Issue65/vandersteen.htm


     While I agree that price does not always equate to quality performance, in the specific case of the Quatro Woods I suggest it does.  

     You stated:
" This may sound picky but it is a matter of definition.  Most often I've seen subwoofer defined as producing the lowest octave of sound, 20-40 Hz.  So a standard woofer may cover bass as far down as 40 Hz.  The crossover for the Quatro passes over to the lowest range at 100 Hz so that would seem to be primarily a bass driver(s)."

     I don't think you're being picky and I'll define excatly how the Quatro Woods function and let you decide what to call the drivers:

Each tower has a 4.5" midrange driver.

Each tower has a 6.5" mid-bass and lower midrange driver, that Vandersteen describes as a 'woofer', that are limited to a frequency range of 100-900 hz.

Each speakeralso have dual 8" deep bass drivers, that Vandersteen describes as 'subwoofers', that operate from 20-100hz.   Room compensation controls, along with bass level contour controls, allow the speakers to be placed where they image best and the bass to be optimized in that position.  The dual 8" drivers in each cabinet are driven by a dedicated 250 watt class B amp.

I consider any driver that is near flat at 20hz, and utilized for frequencies between 20-100hz,  to be a 'subwoofer'. Both the Vandersteen and Swarm deep bass drivers meet this criteria.  Any differences beyond this,  I would suggest get into the area of definitions, semantics and perhaps nit-picking.

Tim .




pryso
1,501 posts
 
Thanks Tim.  My comment was intended for anyone else reading this discussion as much as for you.

I've been in the audio hobby for decades so am likely considered "old school", if not just an old fart.  That's why I adhere to the traditional definitions -- bass = 20-160 Hz, mids = 160-2K Hz (approx.), and highs = 2K-20K Hz.

The range for woofers certainly varies, sometimes extending as high as 500 Hz, so well into the lower-midrange.  But in my experience the lowest octave, 20-40 Hz, is always considered sub-bass or subwoofer range.

I only "nit pick" because I find it helpful to define terms, particularly when any one of them may be considered vague.  I define subwoofer differently than you or Richard Vandersteen, and that is fine so long as each of us is clear about our intent.

Lastly, I've owned three different pairs of Vandersteen speakers and still admire them, but that was some time ago.  I've heard the first generation Quatro but not the current iteration.  By the way, do you know why it is named "Quatro"?

Happy listening. 

noble100's avatar
noble100 OP
1,093 posts
 
Hi pryso,

      It seems like we've both been involved in this hobby a similar amount of time, myself for over 4 decades.  

     I also generally agree with the traditional definitions you listed: bass=20-160 hz, midrange=160-2k hz and treble=2k-20k+ hz. However, I think bass needs to be further defined between mid/upper bass ( ranging from about 30-40 hz to about 160 hz) and deep bass (I would suggest anything below about 30-40 hz).  I'm not knowledgeable enough to stipulate an exact frequency that divides mid/upper bass and deep bass best reproduced by 'subwoofers'.

     My current opinion, on both ht and music reproduction in home sound systems, is that best results are achieved by utilizing 2 separate systems: one for midrange and treble frequencies (using a pair of stereo speakers optimized for best sound stage imaging) and the other exclusively for bass frequencies (using 1 or more subwoofers and dedicated amp(s) and optimized for best bass reproduction through proper positioning that is tailored to each specific room.  I prefer running the main speakers full range and having the bass system's upper frequency cut-off set at just above the main speakers' deepest clean bass capability.  This cutoff frequency will differ based on the main speakers and the room they're set up in.  There is fine tuning and experimentation required when determining the proper upper cut-off frequency of the sub(s) to seamlessly integrate them with the main speakers.  Some may prefer to limit the bass their main speakers reproduce since this considerably reduces the power required from their main amp and eases the demands on their main speakers.  

     I believe the above works best for me in my particular room.  This dual system approach also makes sense to me since it is has been proven that midrange /treble frequencies interact differently to a room than bass frequencies do to the same room.  This is due to the great differences between the lengths of the sound waves each produces.  The lower the frequency, the longer the sound waves become with bass sound waves often being longer than a room's boundaries.

     Toole, Geddes and Welti, among others, have shown that multiple well positioned subs are able to produce accurate and well dispersed bass in any room smaller than a theater or auditorium.  This creates a solid bass foundation or base (a base for bass?) in the room without the need for bass traps or any corrective digital room processing systems.

     Fortunately, the much shorter mid-range /treble frequencies are more easily accomodated than the much longer bass frequencies in most rooms.  Main speaker positioning, along with the possible need for  acoustic panels to control first sound wave reflections,.are all that's needed to create a solid, well integrated sound stage illusion.  The mono bass system integrates seamlessly with the mid-range /treble system without one detracting from the other.   It is highly unlikely that 2 full-range speakers could be positioned in a particular room and be capable of producing such excellent results.  Either the bass or the mid-range / treble performance will typically need to be compromised. I think getting optimum performance of both at specific locations in a room may not even be possible.

Just my thoughts,
  Tim

    

 

     
noble100's avatar
noble100 OP
1,093 posts
 
pryso,

     I forgot to respond to your question on why Vandersteen calls hiis speakers 'Quatro".

     I don't know for certain, but it may have something to do with the speaker being a 4-way design: treble, mid-range, bass and sub bass.  Quatro is spanish  for four and they probably thought 'Quatro Woods'  sounded a bit better than 'Four Woods'.

Tim

     
pryso
1,501 posts
 
Tim, if curious you might verify this with Richard.  This is my understanding.

The first four models of Vandersteen speakers were identified One through Four.  The Four was the top of the line and similar in appearance to the others with a wood cap and bottom and stretched grill cloth covering the boxes and drivers, except it was much larger.  Then after just a few years the Four was the first model to be discontinued.

The next top of the line model was the Five, leaving a gap in the numbering system.  So when a new intermediate size between the Five and Three was introduced Richard identified it as the Quatro because it was significantly different from the old Four, thus hopefully avoiding confusion.

Just don't ask me whatever happened to his Model Six! ;^)

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