Anyone Else Using an Audio Kinesis Swarm or Debra Distributed Bass Array System?
I have Magnepan 2.7QR speakers and posted a similar question about 2 years ago on whether others were using an Audio Kinesis Swarm or Debra or any similar multiple sub distributed bass array system. I thought it might be useful for members to learn about this type of solution for attaining excellent bass performance in virtually any room and with any main speakers for both 2-ch stereo music and ht. I thought a new thread detailing this effective solution may be helpful and attract responses from other users of a distributed array sub system. I’m also wondering if there are any more members using one of these bass systems since I posted my original thread 2 yrs ago.
About 3 years ago I purchased the Audio Kinesis DEBRA (Distributed-Eq BassReflex Array) sub system from James Romeyn Music and Audio in Utah. Here’s a link describing the system:
This system is a bargain at $2,500 and 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 was not convinced at the time of the reality of perceiving 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.
Four 44lb. 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 (flat adapters are also supplied for use on non-carpeted floors) 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 series/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 (mainly Dr.Earl Geddes and Dr.Floyd O’Toole White Papers), 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 produced/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 bass array system. Here’s a link to an Absolute Sound review of the Audio Kinesis Swarm system which is almost identical to the Debra system I own:
http://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-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 updated showing my current system with the subs and new electronics.
Hi, Tim! Thanks for posting your lengthy set up description and experiences with The Swarm. I have been intrigued by this approach and will have a room sized big enough to permit it soon, so I am eager to learn more about it. It sure sounds like you like it it quite a lot. I am hoping others chime in with their experiences, too. |
Hello jrp1, Yes, I'm very glad I took a chance and went with this setup as opposed to my initial intention of 2 very good traditional amplified subs. The Debra system is about the same price but I honestly cannot think of how the bass performance could be improved in my 23 x16 ft. room for music or ht. I was just watching an Epix original series called Get Shorty and many of the episodes have a drum soundtrack. It's basically a jazz type rhythm that consists of a combination of kick drum, snare drum and tom-toms with an occasional hi-hat played. It's very well recorded and the Debra system, with a bit of upper bass and above frequencies supplied by my main panel speakers, results in such an exceptionally realistic, solid, and stable sound stage illusion that the entire drum kit seems to be in the room. The various drums being struck are easily discernible because the bass is so tonally accurate. The bass depth seems to go as low as the content calls for. For example, the kick drum being pedaled is clearly identified not only by its deep and accurate tonal qualities but also by it being felt as well as heard. The snare and tom-toms are also clearly identifiable but more by the accuracy of their tonal and texture qualities alone since the bass is felt less by the body than the kick drum. I think I could probably write a book on how well 4-sub distributed bass arrays actually perform but will spare you and stop short of that on this post..... You're welcome. However, I know actually listening to a properly setup Swarm or Debra bass system, even for a few songs or a movie, would be more convincing to you that it's a state of the art system than a book full of platitudes and superlatives would be. If you haven't already, I'd suggest you read The Absolute Sound review I linked to in my original post. I think it's the best summary of the Swarm/Debra bass system I know of. Hopefully, other users will chime in but, meanwhile, I'd be glad to answer any questions you may have. Tim |
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IMO/IME the Swarm is one of the best subwoofer systems available." Hi Ralph/atmasphere, I've been singing the praises of the Audio Kinesis Swarm/Debra distributed bass array systems ad nauseam ever since I began using one in my system about 3 yrs ago. I had no idea that you're so familiar with the virtues of the Swarm subwoofer system and that you've used it at some shows. Of course, I recognize that my often stated opinion of how well the distributed bass array concept actually works in virtually any room can be, and likely is, often easily dismissed as just the endorsement of a 'fan boy' attempting to rationalize a significant system purchase. I believe your opinion and comment that "the Swarm is one of the best subwoofer systems available", however, understandably carries more weight and may result in more individuals taking the distributed bass array concept more seriously and consider its use in their own systems. It's continued to be perplexing to me why the DBA concept is not more widely known and utilized, especially by members of an audiophile forum and the fact that the concept has been scientifically proven while also being validated repeatedly since both scientifically by many and anecdotally in their own systems by apparently just a handful. Most are aware that good bass response is typically harder to attain in most systems and rooms than good mid-range and treble response. Using and knowing that a DBA is such a good universal solution that seems to improve bass response almost magically, I was motivated to try to spread the word. But I remain a bit confused and frustrated that more individuals are seemingly not embracing the DBA system solution. Thanks, Tim |
I had used Duke’s AudioKinesis Jazz modules for many years and was always intrigued by the Swarm. I actually took a slightly different route. I use a 4 woofer array the concept of which came from Roger Modjeski at Music Reference. The boxes have a smaller footprint (1.4 cu. ft. internal dimensions), use 8" drivers, and are sealed. Their resonance is 100 Hz. I use the Beveridge RM-3 active crossover with 4th Order Linkwitz-Riley 100 Hz high and low pass filters. The amp is a Luxman M-02 which I like because it has two sets of speaker outputs so I can attach one pair of woofers to the speaker A binding posts and one pair to the speaker B binding posts. I just placed the woofers asymmetrically around the room and was done with it. Occasionally I like to invert the leads on one or more of the woofers to hear the different effects, but I just end up switching them back. I am curious about your series/parallel set up and the reasoning behind it. It may be something I might like to try. |
Hi clio09, The series/parallel hookup for the Swarm/Debra systems is what Audio Kinesis instructs in the manual. I had never heard of series/parallel connections and always thought wiring connections could be done either in series or parallel but not a combo of the two. As I understand it, the series/parallel connection method is used because the amp operates under a recognized single 4 ohm load even though the amp is actually powering four 4 ohm subs, 2 each on both the A and B speaker outputs on the class AB 1K watt amp. It’s interesting that you occasionally invert the polarity on 1 or more of your subs. The Swarm/Debra manual also instructs to try this on each sub sequentially to determine if the bass sounds better with the polarity inverted one particular sub of the 4. I haven’t bothered trying this yet since the whole system is performing so well as is. Have you noticed beneficial results from doing this? Your system also demonstrates an important factor when configuring an effective distributed bass array system: the critical requirement is using 4 subs so that the vast majority of bass standing waves are eliminated and, therefore, bass response performance is maximized. The main points being that the subs don’t need to be a complete set of 4 Swarm/Debra subs, of the same brand or even of the same size. The critical points being that 2 subs will perform better than 1, 3 will perform better than 2, 4 will perform best and any subs added beyond 4 will result in only smaller marginal improvements in in-room bass response Tim |
Tim, My understanding is that inverting one of the woofers would further reduce bass energy. I did try it but did not notice a difference. Probably because I lucked out and placed the woofers in proper positions from the get go. Inverting two woofers was noticeably worse. I doubt I will try the series/parallel connection. My woofers are 8 ohms and the amps speakers connections when using the A & B speaker connections recommend an 8 - 16 ohm load. |
Hi clio09, I'm with you, I don't perceive a need to experiment with the polarity on any of the 4 subs. I could be wrong but would expect if there are any benefits to inverting polarity, they'd probably be very subtle. It sounds like you placed your 4 subs in the most convenient spots in your room and think you lucked out because the bass performs so well. If this is the case, you may be surprised with some more obvious and significant bass improvements possibly attainable through the Audio Kinesis recommended setup method (detailed in my initial post) that positions each sub sequentially and more precisely. Just to be clear, however, I cannot definitively state better bass response will result in your system from following the Audio Kinesis recommended procedure than your more random current setup. I have no experience with comparing the two methods since I've only positioned my 4 subs using the recommended method and have never used the random method. It may be worth a try, though, if you have the time and inclination. But, on the other hand, I know through reading the results of research on this subject that even randomly placing 4 subs in a given room consistently results in improved bass response; just the existence in the room of 4 subs will decrease the quantity of bass standing waves and thus improve bass response. I believe the only way you're going to know which method produces the optimum bass response in your room is to try the recommended method and determine if you perceive an improvement. I can definitely state that the recommended procedure resulted in a couple obvious improvements in my room: - High quality bass response not only at my listening position but at all 6 seating positions in my living room. This may not be important to you but, if it is, you can test your current distributed bass array system's performance by comparing the bass response at other seating positions in your room (or just at various spots walking around your room) with the response at your preferred listening seat. - Of course, even if bass response is optimized throughout the entire room, the remaining frequencies and the sound stage illusion can only be optimized at a single 'sweet spot' listening position. The recommended method, fortunately, did allow the bass to be perceived as originating from the proper position within the sound stage illusion in my room. Whether you decide to try the recommended method or not, I think we're both in the cutting edge realm of in-home bass response performance. My experience is that upgrading from the good and acceptable bass response of a dual sub setup to the state of the art bass response of a 4 sub distributed bass array setup is a significant improvement that I would describe as revelatory and stunning. I've found it hard to accurately describe how exceptionally well this concept actually works. I believe just listening to one for only a few minutes would likely be a more effective method of convincing almost anyone. I was convinced after listening to a single song after setting up the Debra system. Tim |
Hello clio09, Good point about not needing any bass room treatments when utilizing a 4 sub distributed bass array. The entire concept of producing bass in your room and then trying to reduce the bass and inevitable bass standing waves (that cause mathematically predictable spots in any given room where the bass is perceived as over or under emphasized and even completely absent) by using large and expensive bass traps has always struck me as wasteful, ugly, generally ineffective, hit or miss and extremely silly. Properly positioned 4 sub distributed bass array systems not only eliminate the need for these ridiculous bass room treatments but also eliminate the need for any equalizers, mics and room correction software and hardware. Tim |
@atmasphere - I got my first exposure to the swarm" set up I have today in one of my rooms at Newport a few years ago, so I know exactly what you mean. First time I could set up a room and not have to fiddle around all day or night getting the bass to sound good. I didn’t know what to do with all the extra time on my hands. It seems digital room correction is quite the rave now. I can’t say I have any measurable level of experience with it, but glad I can bypass it altogether. |
I run these systems: 1. Biamp: Acoustat Model 2 (modified panels) with Acoustat servo amps (direct drive, no transformer interface) driving the panels, Beveridge RM-3 active crossover (100 Hz 4th order Linkwitz-Riley high and low pass filters), Luxman M-02 powering the woofers. So the panels play everything over 100 Hz and the woofers 100 Hz and below. 2. Biamp: Same as above except Quad ESL-57 powered by Atma-Sphere M-60s. I also run the ESL-57 and M-60s without biamping and the bass is quite good in that set up as well. |
Hello amg56, Welcome to the party. The reason I, and I think the other users of 4 sub distributed bass array systems on this thread, have not mentioned or discussed their main speakers and amps is because we understand it's irrelevant; this concept performs and integrates exceptionally well regardless of the main speakers and the amp(s) driving them. My system is a fairly good example of this benefit. My main speakers are 6 x 2 foot Magnepan 2.7QR planar panels driven by a pair of 1,200 watt class D mono-blocks. Planars and electrostatics are considered to be 'fast' speakers that are difficult to integrate conventional subs with because they' usually are much slower, have difficulty keeping pace with 'fast' type speakers and the bass tends to lag behind, making the bass sound disconnected and poorly integrated with the mids and treble from the 'fast' main speakers. The Debra system I use integrates seamlessly with my mains panels both with music and ht. I hope this cleared things up for you, Tim |
Thanks for the awesome and informative post! I started on another thread discussing woofer size and followed your link here. Great info and nicely presented. You got me thinking...! I’m a little unclear on the amplification end though. Forgive me, you probably clearly addressed this but I got really focused on the acoustical aspects and now instead of re reading I’m being lazy and asking.haha Does this involve a special and dedicated amp or a receiver equipped with the technology? I remember reading "any four subs" ; does that mean the size and type don’t matter? My room is kind of small. It’s 14×22 but due to doorway/closet configuration I’m forced to orient front/rear on the 14’ and only able to use 16’ of the 22’ for speaker placement and that leaves 6’ of space on the left channel which is sonically killing me!!! This (one of a few ) system is in the main living room and therefore used for music and theater. It mainly consists of an older and higher end Onkyo THX 5.1 reciever, Definitive BP-2000 (each speaker has its own powered 300 watt 15" sub) mains, Definitive surrounds, an Atlantic Technologies center (that I couldn’t be happier with!) and until recently a high end Polk 10" sub that was tuned to its lowest (until recently) pass. I couldn’t understand how I blew it up until reading your post and I’m not at all unfamiliar with acoustics but you described exactly what I believe happened! I guess I should have mentioned that I recently moved in to a new home... After setting up the system and being nothing but disappointed I started trying different tunings and settings...no matter what I did/do I’m disappointed in a system I have loved for years! Now I know after reading your posts that the dynamics of the room were cancelling out frequencies that I knew were missing so I just kept feeding it more power and turning the crossovers up until the Polk could take no more even though there was no audible distortion. Sorry for rambling on, ultimately my question is about the amplification and do you know if I could incorporate my main speakers as part of the array or is that 6’ void in my available space going to wreak havoc no matter what I do? The mid and high frequencies sound perfect as they are directional but I’m a full range fanatic and I NEED my bass! If I could afford them I'd have subs that went all the way to 14htz even though you can't hear it, you can feel it! In the past I had a perfect blend of pop and boom but now it’s completely lack luster... |
Here is the amplifier used in the Swarm/Debra set up. You just need 4 passive woofers to connect to the amp. https://www.parts-express.com/dayton-audio-sa1000-subwoofer-amplifier-rack-mountable--300-811 I use a different set up as described in one of my posts above, but the objective is the same. Also, I built my own woofer boxes and bought off the shelf 8" drivers. My goal in a 12 x 20 room was a more compact footprint for the woofers. Then for aesthetics I had the boxes painted with Jaguar black automotive paint. |
magzxi, Sorry, I just noticed your post requesting advice from 8/19/18. But it looks like clio09 covered for me with accurate info on the amp supplied with the Debra system. Yes, the 15" subs built into your BP-2000 main speakers would count as 2 of the 4 subs used in a custom DBA (distributed bass array) system. But there’s a specific setup process you need to follow for best results that I can explain to you later. You’ve stated the mid and high frequencies sound perfect to you in your current system setup. This is very good but I need answers to a few questions before I can help you further: 1. Do you have only 1 listening and viewing position/seat in this room or multiple seating positions? 2. Do you plan to build or buy the additional 2 subs required? Remember, the Dayton amp requires 4 Ohm subs, not 8 Ohm. 3. Is there anything along the 2 long side walls and shorter back wall in your room? Tim |
Thanks for the help! I've read the thread over again quickly and don't see the difference between SWARM and DEBRA. What am I missing??? It seems as though any good sub amp could be used. Is that correct? Thanks Tim, to answer your questions in order... 1) There are two couches and one recliner in the room. I have a sweet spot and everybody else gets what is left! Haha! 2) I'd have to do some serious research about that! First of all I'd have to wire the BPs passively which is forsaking a 300w rms class a/b amp on each speaker. The BPs dig all the way down to 15hz as they are. I'd want to be able to match that with the DEBRA. The other two speakers... good passive subs are not hard to build but if I could find a nice set of equal caliber for the right price... 3) As for the room dimensions it sounds like you are interpreting them 90° out of actual orientation. The long walls are front to back and the short walls are left to right. That automatically sucks but to suck it up even more; due to passageway and door configuration there is a 5' unusable space front to back on the left side! That's what is killing me!!! Highs are directional frequencies while lows are omni directional and radiate from an epicenter as you know so that void on the left is KILLING my bass response! What intrigued me about your post was the explanation of how these unequally refracted bass frequencies could cancel each other out. I can attest! Thanks for your help Tim! |
"Thanks for the help! I’ve read the thread over again quickly and don’t see the difference between SWARM and DEBRA. What am I missing???" "Hello magzxi, The AK Swarm and Debra dba systems are basically identical. The Swarm is retailed by AK founder and owner, Dick Lejeune who I believe passed away in 2017, and the Debra is retailed by his associate and AK dealer, James Romeyn, founder and owner of James Romeyn Music and Audio LLC. If interested, I’d suggest calling James Romeyn in Utah to verify I’m not missing something. and if he sells both now They both look the same, perform equally well,are the same price and I believe have the same setup procedures. " 2) I’d have to do some serious research about that! First of all I’d have to wire the BPs passively which is forsaking a 300w rms class a/b amp on each speaker. The BPs dig all the way down to 15hz as they are. I’d want to be able to match that with the DEBRA. The other two speakers... good passive subs are not hard to build but if I could find a nice set of equal caliber for the right price..." You can still use the 300w class a/b amps and subs in each of your speakers. These would count as 2 of the 4 subs required in a custom dba system you’re considering. You could research the subs used in your BP speakers and try to find a source to buy j the same drivers and build your own subs, even possibly buying a similar plate amp for each (instead of building passive subs and using the Dayton amp) if you’d like. You could also buy 2 powered subs ( new or used).or buy the Dayton or other sub amp and buy or build 2 passive subs of whatever size and specs you'd like.. The important factor is having 4 subs, they don’t have to be the same brand, size or type. The setup procedure is also important but I can explain exactly how to locate your subs once you make a decision on the above. "3) As for the room dimensions it sounds like you are interpreting them 90° out of actual orientation. The long walls are front to back and the short walls are left to right. That automatically sucks but to suck it up even more; due to passageway and door configuration there is a 5’ unusable space front to back on the left side! That’s what is killing me!!! Highs are directional frequencies while lows are omni directional and radiate from an epicenter as you know so that void on the left is KILLING my bass response! What intrigued me about your post was the explanation of how these unequally refracted bass frequencies could cancel each other out. I can attest! " Yes, I was misinterpreting your system configuration but now understand the long walls are front to back and the short walls are the side walls ( my 23 x 16 ft room is configured short walls front to back and mistakenly thought your’s was the same.) As far as bass response, either way will result in great bass response as long as they are properly positioned according to the 4 sub dba recommended positioning procedure. I’m not certain, but I don’t believe the 5’ of unusable space will negatively affect the bass response. You already stated that you’ve got the more directional mid and high frequencies sounding very good so you should be good if the bass response improves. You just need to decide what 2 additional subs to buy or build and how to power them. Tim |
Hi Tim, Thank you very much for your enthusiasm and expertise about distributed multi-sub systems. I would however like to take issue with one thing you said: "The Swarm is retailed by AK founder and owner, Dick Lejeune who I believe passed away in 2017..." Far as I can tell I haven’t passed away yet, or if I have, I’m stuck in a limbo that is thus far indistinguishable from an Audiogon thread. Fortunately it’s a thread where people are saying nice things about my stuff! Just for the record, I got the distributed multisub idea from Earl Geddes. It happened like this: I was driving Earl to the airport after CES in January of 2006 and we were stopped at a stoplight. He said to me "Duke, I’ve figured out how to get good bass in a small room. Use four small subs and distribute them asymmetrically. Each will produce a different room-interaction peak-and-dip pattern, and the sum of the four dissimilar peak-and-dip patterns will be much smoother than any one alone." A lightbulb went off in my head as I immediately realized this was "the answer", so I said, "Can I license that idea from you?" He replied, "You can just use it." And then the light changed. It was that fast. Now let me explain what I meant by "the answer": For years I had been trying, off and on, to build a subwoofer that was "fast enough" to keep up with Quads and Maggies. I was a SoundLab dealer, and the SoundLabs are big enough to have good low-end extension, but they are too big and expensive for most people. I figured the first guy to make a sufficiently "fast" sub would have a potential market among Quad and Maggie owners. Being a longtime amateur speaker builder, I tried pretty much everything except for a horn: Sealed boxes, aperiodics, low-tuned vented boxes, transmission lines of many different geometries, equalized dipoles, and isobarics. None of them could "keep up" with Maggies and Quads. I was stumped. But the problem was not the "speed" of the subwoofer - it was the peak-and-dip pattern that the room inevitably superimposed on the sub, which totally dominated the result. Yes some subs were audible improvements over others, but none could blend with Maggies or Quads without there being a distracting disconnect between the subjective lack of "speed" in the low bass and the rest of the spectrum. You see, woofer(s) + room = a minimum phase system at low frequencies. What this means is, the frequency response and the time-domain response track one another. In English: Where you have an in-room response PEAK is where the decay is SLOW, and it doesn’t matter how "fast" the woofer is. The good news is that, when you fix the frequency response you ALSO fix the time-domain response, and vice-versa! So, SMOOTH bass is FAST bass. This is why the lightbulb went off in my head when Earl described his idea to me. A distributed multisub system like the Debra or Swarm or your own set of four subs results in four (inevitably nasty) peak-and-dip patterns, but their sum will be much smoother than any one of them. Actually you will end up with MORE peaks and dips, which will be much smaller and much closer together. This "closer together" part is quite beneficial - the ear tends to average out peaks and dips that are within 1/3 octave of one another. So the subjective improvement is often greater than one would expect from merely eyeballing before-and-after curves. One of the things to be aware of if you’re going to "roll your own" distributed multisub system is this: At the upper end of the bass region the outputs of the subs will be combining in semi-random phase, but at the bottom end of the bass spectrum their outputs may well be combining in-phase or nearly so, if the longest room dimension is a small enough fraction of a wavelength. This results in a rising response as we go down in frequency (and remember that the time-domain response tracks the frequency response). So if you already have two subs that go real deep, you might do better by adding two more that do not go as deep. Or vice-versa. In the Debra and Swarm systems, the subs’ native response curve falls by about 3 dB per octave from 80 Hz down to 20 Hz. This approximately compensates for typical room gain. Then in most rooms we reverse the polarity of one of the subs (usually the one farthest from the main speakers), and this extends that semi-random-phase addition down into the bottom of the bass region, further smoothing the response and offsetting the rising bottom end that we would otherwise have. Also the down-firing ports on the Debra and Swarm modules are pluggable, converting the enclosure into a low-tuned sealed box, to give further adjustability (given that every room is different). And finally, the amp that we use has a single band of parametric EQ, in case there is still a peak at some frequency. Speaking of EQ, why not use a single sub with EQ to fix the frequency response curve, simultaneously fixing the time domain response? EQ works great at a single listening position, and can work well within a small listening area. But the larger the listening area that we try to improve with EQ, the smaller the improvements are going to be. This is because the afore-mentioned room-induced peak-and-dip pattern changes dramatically as we change locations within the room ,so EQing a single subs works best for a single location. Unfortunately when we fix the frequency response in one location, we are making it MUCH WORSE in other locations! This is because the peaks and dips are at different frequencies at other locations. But with a distributed multi-sub system, the spatial variation (difference in frequency response from one location to another) is also greatly reduced. So if by chance there is still a peak with a distributed multi-sub system, chances are it’s a GLOBAL (room-wide) rather than a LOCAL peak, and therefore is a very good candidate for correction via equalization. Big rooms have smoother bass than small rooms because they have a more dense modal behavior: The room-induced peaks and dips are more numerous and more closely spaced. A distributed multisub system can make a small room mimic a larger room in the bass region by doing the same thing. And this will sound counter-intuitive, but the smaller the room, the more it will benefit from a distributed multi-sub system. One other bit of trivia: The other main researcher behind distributed multisub systems is Todd Welti of Harmon International. He investigated symmetrical rather than asymmetrical arrangements. Anyway Earl and Todd were developing their ideas AT EXACTLY THE SAME TIME, but each was completely unaware of the other’s work. So I guess it was an idea whose time had come! Robert E. Greene of The Absolute Sound gave the Swarm a Golden Ear award again this year (It got a Product of the Year award back in 2015). So despite the passage of time, apparently the distributed multisub idea hasn’t become outdated. Duke dealer/manufacturer/caught in limbo? |
Magzxi posted: "Thanks for the help! I’ve read the thread over again quickly and don’t see the difference between SWARM and DEBRA." The Swarm is Duke’s design, square footprint. The DEBRA is Jim Romeyn’s variation on the theme, with a rectangular footprint. Same woofer + very similar internal volume + the same port dimensions = very similar performance, but the DEBRA modules don’t stick out into the room as far, and so in most cases win the aesthetics competition. Jim has an artistic side and Duke does not. My recollection is that the DEBRA modules have a little bit more internal volume, so they might have a little bit more output down around 20 Hz. Jim and I will be showing a system at Rocky Mountain Audio Fest that will draw somewhat on our experiences with distributed multisub systems. Room 3002, in the Tower. Duke |
Hello Duke, First, I am thrilled, as I'm sure you are, to discover that you're still alive and kicking! I am thoroughly embarrassed and want to apologize profusely for my bone head mistake. I wanted to find out a bit more about you and mistakenly googled 'Dick Lejeune' instead of 'Duke Lejeune'. Dick Lejeune passed away on 2/18/2017 and I didn't notice I had renamed you on my Google search until I read your post today. Honestly, I realize my explanation just further demonstrates my stupidity but I couldn't care less because.... YOU'RE ALIVE AND STILL WITH US!!! Secondly, thank you very much for your very interesting post on the AK Swarm and Debra beginnings and the finer points on how and why distributed bass arrays work so well. I was originally very skeptical about whether the Debra dba would work in my room (23' x 16' with 8' ceiling and a 6'h x 8'w window along one of the 23' walls) and my system (combo computer audio music and 5.1 surround ht system consisting of a laptop running JRiver software, 2 TB NAS, Oppo 105, class D amps, 'fast' Magnepan 2.7QR large mains panels and CC3 center along with traditional cone in-ceiling Infinity rear surrounds). My initial bass improvement plan was to get 2 high quality conventional self- amplified subs. I was talking to James Monteyn about having a pair of Hypex NCor class D mono amps built when he first informed me about the AK Debra dba system as an alternative that would provide sota in-room bass response in virtually any room. I recall thinking at the time that the Debra/Swarm dbas, at about the same price as a pair of good quality subs, sounded too good to be true. I was also a bit concerned about accommodating the 4 subs in my combo A/V and living room. But I then read all I could find online about dba theory and practical uses, mainly Earl Geddes and Floyd O'Toole material, and it all began to make a lot of sense to me. I continued to have good discussions via phone and email with James Romeyn and, when he offered a free 30-day in-home trial period with purchase, I decided to give the Debra system a try. I think I'll be eternally grateful that I decided to give the Debra a try. I've posted many times on Audiogon about how well this system has worked in my room/system. I believe I could write a book about how almost magically the Debra dba transformed bass response in my room and system from mediocre to truly excellent.and, as the 2015 Absolute Sound review accurately stated, provides state of the art in-room bass reproduction. In fact, this concept works so well that I have perpetually felt an obligation to spread the word and sing the praises of the Swarm, Debra and really any "roll your own" dba system on almost any posts that inquires about improved bass response or the 'best' sub to use/buy, I'm fairly certain many frequent thread readers likely know my common refrain by now and roll their eyes when they begin reading another of my bass posts. I'm generally not too concerned because the truth is the truth regardless of what Trump and Guilliani may say. My current opinion is that most readers won't be convinced about how well the Swarm/Debra and custom dbas work no matter how many thoroughly honest testimonials they read from myself and others or even rave reviews on the AK Swarm by The Absolute Sound. Yet I'm almost certain that just a few minutes of listening to the sota bass response these distributed bass arrays provide in person would convince virtually everyone. Do you notice this discrepancy between descriptions and actual personal auditioning in your experiences? It continually perplexes me, and it must be constantly a bit frustrating to you and James, why there seemingly aren't more users of high performance dba systems, especially by members of a high performance audio site like Audiogon. I would think they'd be selling like hotcakes and used in many more systems after multiple Golden Ear awards and a rave review along with a Product of the Year award back in 2015. Thanks for telling me about your room at Rocky Mountain Audio Fest, I'm going to try to make it out there to see you guys and check out your room. Sorry again for my idiotic misstatement, I'm so glad you're still with us! I wish you a long and happy life with continued prosperity, Tim |
@noble100 I like the concept of the DEBRA, but unfortunately have pretty much every inch of wall space accounted for (it's a multi-purpose room--listening room, family room, office), and enough openings for doors that running cables is a challenge. Using bass traps and room treatments for bass is also nearly impossible given the layout. But I wanted to experiment nonetheless, and I found two wireless subs from Martin Logan so I could give it a try. (My main speakers extend down into the upper 20Hz range, the MLs into the mid 20s.) Given the challenges, I decided to split the output at my preamp and send one of them to a MiniDSP for now, as one of the subs was in a particularly boomy part of the room, and I also time-aligned them to the main speakers. (The MiniDSP has four outputs, so, I can use up to four subs with it.) Placement--one is off to the side, and the other is to the side/rear in an opening to the kitchen. Even with only two subs, it's a major improvement in bass! My only possible listening position in the room had a major bass suckout, where anything under 60Hz was nothing but wishful thinking. At first the additional subs were way too boomy, but I kept dialing them back until I thought they weren't even working. That was the trick. At the listening seat now, I hear *all* the bass notes in, say, classical or jazz at an even level, much cleaner and deeper than before. Most of the time, I have to walk over to the subs to make certain they are working--they are that low in level. The effect also covers a larger area of the room--I'm finding the bass evened out throughout the listening end of the room. I do plan on adding two more subs and doing this "officially" per the instructions, but even with the two subs, I find it cured a lot of my existing problems in the room. For not much of a cash outlay, I was able to (roughly) try it and see if the concept would work, and it does. I'll probably spring for the "real thing" once we move in a few years and I can have a more flexible arrangement in a listening room. It's definitely worth the investment in time and money. |
Hello shoresaudio, Yes, as the owner of Audio Kinesis, Duke Lejeune, likes to say: "Two subs will sound twice as good as one. Four subs will sound twice as good as two. And 8 subs will probably get you divorced." As you've discovered, the bass response starts to improve (more detailed, smoother and over a larger section of the room.) significantly once you have two subs operating in the room. I'm glad you like the results thus far and you should notice another significant improvement going from two to four subs in your new room. I'd just suggest following the sub positioning procedure as closely as you can. You've already gained good experience realizing how setting the crossover frequency and volume of the subs as low as possible makes the blending of the subs with your main speakers more seamless. I've been trying to spread the word on how well the 4-sub distributed bass array (DBA) concept actually works and I'm glad you're a new member of the DBA Club. Best wishes, |
jdlynch:"Could a system like the HSU ULS15 quad system be made into a swarm array?" Hello jdlynch, The answer is a definite Yes. A custom 4-sub distributed bass array (DBA) system can be created utilizing any four subs one chooses. The subs don't even need to be the same brand, model or even size to produce excellent bass performance results in virtually any In fact, a custom DBA consisting of four HSU ULS15 quad subs would certainly outperform an Audio Kinesis 4-sub Swarm/Debra complete kit DBA in bass power and dynamics as well as likely at least matching it in bass smoothness and integration with your main speakers. It may even equal the Swarm or Debra bass speed and detail, too, but I'm not certain. The main downside of a custom DBA, utilizing four conventional self-amplified subs, is that the three main settings (volume, crossover frequency and phase) would need to be set optimally for each sub individually rather than once for all four subs optimally as a group on the included sub amp/control unit with the Swarm/Debra complete DBA kit. I don't know the price of four Hsu ULS15 subs so I don't know if it has a price advantage over the $3K price of the Swarm/Debra DBAs but it does have the advantage of being wireless. Based on my sub experience with Magnepan main speakers, I can state with certainty and in general that 2 subs sound twice as good as 1 and 4 subs sound twice as good as 2. I believe the threshold for attaining near state of the art in-room bass performance in any room is reached by deploying 4 optimally positioned and configured subs. Fewer subs can definitely perform very well but the bass will likely be compromised and not optimized in all bass performance qualities. Tim |
