Dual vs single sub


Sorry Im sure this is all over the forums but I only found old articles. Situation. I have Two SVS 3000s that arent really doing it for me. Thinking of trading it in on the Big one and adding another in a year or so. Any thoughts on Big single vs 2 Medium?
8871b9f2 ca67 4c66 a5a3 2c6e70d4aaadbryantdrew
Hello hifidream,

    Congratulations on creating your own custom distributed bass array system for your Magnepan20.1 speakers. I know the 20.1s have very good bass performance in stock form with 2 large planar-magnetic bass panels in each speaker that all output down to 25 Hz. Not full extension to 20 Hz like many good subs but close and very respectable.
    Counting each pair of bass panels as a sub, I would suggest you're actually using a total of 6 subs in your room/system. While 2 aren't outputting bass that's fully extended, they're both outputting the exceptionally fast, articulate and smooth bass provided by planar-magnetic panels down to a deep bass level of 25 Hz.  

      Since we've both experienced the amazing seamless integration with even fast planar-magnetic panel speakers (whether mid-level models like mine or top of the line models like yours) and the high quality bass produced using 4-sub dba systems, I think it's safe to assume you'd agree that the dba concept works exceptionally well.

Tim
phusis you are right. A point source system can be wonderful with two subs set up correctly. A line source requires four subs in most rooms (wall up to 16 feet). Now I am going to make some people mad. Distributing the subs through out the room makes no sense. Once the subs are more than 5 to 10 feet apart depending on cross over point they act as two completely separate drivers with 2 separate interference patterns in the room. At 10 feet you would have to cross over below 40 Hz. Systems benefit greatly from high pass filters. It relieves the main amp from having to produce low frequency transients which require a lot of power. They also eliminate Doppler distortion from the satellite low frequency drivers cleaning them up. You get more improvement the higher you cross (but not too high). But with distributed woofers you can't cross above 80 Hz or you screw up the image (some would say lower). If you want the most benefit from multiple woofers, the lowest distortion from your satellites,
A great image and absolute thundering bass with the lowest room interference, set up the four woofers along one wall right up against it symmetrically in regards to the satellites right and left channels. The far woofers should go right in the corners, the near just to the inside of the satellites. Cross over between 100 and 130 Hz 12 to 24 db/octave and use high pass filters. Don't believe me. Try it for yourself if you have the equipment. I do have the equipment and I have been using multiple subs since 1979 and have set them up in every configuration you can think of using every conceivable cross over. Experience is always the best teacher. Aside from listening to music this is where the fun is in this hobby, playing around with your system. Once you have the equipment you can play around with the configuration room constraints allowing. As long as you are a good listener you are in business. Back to Stravinsky! 

@audiokinesis --


The distributed multi-sub approach has nothing to do with whether or not the mains are highpassed. Those are two separate decisions. I’m probably the one who caused the confusion because I’m a distributed multi-sub advocate but not an advocate of automatically high-passing the mains in every situation. I think it depends on the specifics.


I know, Duke re: multi-sub approach and high-passing mains, but I brought this into the mix, so to speak, because it's my impression the general gist with multi-sub use is to cross fairly low to the mains (i.e.: without high-passing them), not least taking into account the directionality at higher frequencies and how this could be seen as an issue with subs scattered throughout the room around the listener. 

I did refer to high-passing the mains as a "potential benefit," which is also a way of saying that I side with your view on how it "depends on the specifics." 


The distributed multi-sub approach apparently works well in many situations, but is not the only approach that works well, and in some situations it would not be the approach I'd choose. It depends on the specific situation. 


I believe this has always come across rather consistently from your writings, certainly implicitly, contrary to other advocates here of the 4-sub approach who seem quite adamant of it being the only true quality solution, so much indeed that considering otherwise is "not getting it." Again, I've heard great 4-sub setups, no contention here, but I believe a symmetrically placed 2-sub setup can make wonders as well.

phusis:
" Why try and make a case with a limited number of CD’s (what genre, age of mix, etc.?) to conclude that there’s virtually no recorded true-stereo bass?"

Hello phusis,
     I don't believe it was millercarbon who tried to make a case that there's virtually no recorded true-stereo bass content.    I think it was Audiokinesis/Duke who mentioned the rarity of recordings with stereo bass earlier on this thread.
    I know that his AK Swarm and Debra distributed bass array systems, with the addition of a 2nd Dayton sub amp, is capable of being positioned in a manner that would successfully reproduce stereo bass.
    If I recall correctly, however, Duke stated he wasn't aware of any content containing true-stereo bass and asked if anyone else knew of any content recorded with true-stereo bass.  I'm not aware of any and apparently no one else reading this thread is, either.  
     You seemed a bit offended when you mistakenly thought millercarbon had tried to make a case that there was just a 'limited' number of cds containing true-stereo bass when there appears to be none.      
     Are you aware of any recorded content with true-stereo bass?
     Just to be clear, I know it's very possible to attain very good bass response at a single sweet spot location using 2 good subs.  My point is that it will be very good mono bass, not true-stereo bass.

Tim

@phusis wrote, about the distributed multi-sub approach: "... not drawing on the potential benefit of high-passing the mains (from ~80Hz or so on up to make the most of it."

The distributed multi-sub approach has nothing to do with whether or not the mains are highpassed. Those are two separate decisions. I’m probably the one who caused the confusion because I’m a distributed multi-sub advocate but not an advocate of automatically high-passing the mains in every situation. I think it depends on the specifics.

"...it’s not my intention to bash the multiple sub approach, which I know can sound great, but for some to ease up a bit on this being the only proper way to implement subs in your home setup."

The distributed multi-sub approach apparently works well in many situations, but is not the only approach that works well, and in some situations it would not be the approach I'd choose.  It depends on the specific situation. 

Duke

@millercarbon --

The Ford Motor Company did a study some years ago, to determine what exactly was needed for really good bass. What they found is that below something like 80 Hz the bass on virtually all recordings is mono.

I just got my Swarm-based distributed bass array up and running last night and so I can now say from factual actual experience there is nothing else like it. If you want really good bass you will use FOUR subs distributed around the room. Period.

Why try and make a case with a limited number of CD’s (what genre, age of mix, etc.?) to conclude that there’s virtually no recorded true-stereo bass? It’s the problem of induction all over again, and a neatly sought closure to support an argument that may know full well the problematic issue of playing stereo information from sound sources (i.e.: subs) that aren’t placed symmetrically to the mains, insofar they’re crossed high enough for it to matter (which, I’d wager, could be an issue even if crossed below the rigidly fixed 80Hz). So, mono is the solution, preferably crossed rather low for the 4-sub approach to make the best of it, timing with the mains being the lesser concern and not drawing on the potential benefit of high-passing the mains (from ~80Hz or so on up to make the most of it). At times this even boarders on the scent of a subwoofer inquisition that calls heresy on anyone who’d dare not to see the divine light of multiple subs.

Fore sure, multiple sub sources scattered throughout the listening room in mono can sound absolutely great - the latest of which I’ve heard comprised no less that 6 Front Loaded Horns each fitted with a 15" driver tuned at ~25Hz (20 cubic feet cabinet volume per horn), and it was a blast both in quality and quantity (that is, 4 of them were placed front center from the ceiling in a cluster with all mouths facing each other to form a single mouth, while the last 2 of them were placed along the rear wall, so essentially this wasn’t a multiple sub approach as advocated here).

What really annoys me though is a prevalence to factualize a sub-approach (i.e.: the 4-sub mono one) as the one and only high quality solution, when there are other viable solutions like a 2-sub approach - in stereo, crossed significantly above 50Hz, and placed symmetrically to the mains. If mono-bass is your thing, or certainly the argument of it, then a pair of stereo-coupled subs will still play a mono signal as such, but if classical material or electronica in particular should muster up a stereo signal here for an intended effect or to support a spatial element, then true stereo-coupled subs placed properly (to the mains) will grant you this aspect of the music additionally.

Further I’d suggest being open to other principles than direct radiating subs, which are by far - dare I say exclusively - the bass principle of choice around here and audiophilia in general, perhaps even blindly. Horn subs aren’t really sold commercially other than from pro vendors, and while also being quite large it’s understandable many mayn’t have been exposed to their traits in a home setting, but this is also the problem: most simply don’t know how horn subs sound, and because of this (and their being used in pro-sector applications) likely make assumptions on their sound that are far removed from their actual imprinting. Quality horn subs, which are mostly available via DIY-solutions, to my ears sport a level of refinement, ease, smoothness and enveloping presence that no direct radiating solution that I’ve heard can equal, and this is obvious whether a multiple sub approach, 2 of them or even singles is used. While you would think first and foremost that a horn sub (some 30Hz extension minimum requirement for it to be called a ’sub’ and not just a bass bin) to be perhaps more of a more brutal, chest-slamming experience than a smaller DR solution (which it can be at elevated levels), you’re likely oblivious to the traits mentioned above that are prevalent at more normal listening levels as well (i.e.: 60-90dB’s, whatever floats your boat) - traits that should be considered and pursued by every audiophile.

So then, it’s not my intention to bash the multiple sub approach, which I know can sound great, but for some to ease up a bit on this being the only proper way to implement subs in your home setup. 

EDIT: one could of course combine a true stereo 2-sub setup with 2 additional subs in mono placed more "freely" in relation to the mains. 
Hi Tim,

    I have two Kinergetics SW-800s (each has five 10” Seas drivers in their own enclosures wired in parallel) driven by a Pass Labs X-250 and two SVS SB-16 Ultras in my room. I have an active set up using a Mac Mini maxed out with SSD drives using JRiver playing lossless FLAC to my mini DSP via optical out. The mini DSP is processing 24/96 with 8 balanced outputs with 12 biquad filters on each channel which were created using REW and MSO. My main speakers (Magnepan 20.1’s) run full range. Highs/Lows of each Maggie have their own channels (4) and each sub has its own channel (4). 

To tackle the Herculean task of attaining perfect base I have spent almost as much money on my subs as my 20.1s. That is how much I believe it is important to get this aspect of the system correct. Proper base is essential to all music, I want a tympani to sound like it and make my chest reverb with a strike as it did when I played in an orchestra. Lower octave listening, even the vibrations you can’t hear but feel are foundational to the live experience. Those waves are dissipated in a concert hall but build up in a room and bloat the sound unless it’s done right. I’ve heard a lot of excellent systems and many top of the line speakers will not tread near 16Hz because they know it will be a mess in most rooms. 

While i get that many people will not go to my extreme to get perfect base having 4 subs of reasonable quality disbursed in the room can really make a system sound complete. When properly set up the bass is tight and integrates seamlessly into the system.

The most common statement upon seeing my set up is, “I bet you could blow out the window with that! Why do you have so many big speakers?” “It’s for accuracy,” I say and then ask to play their favorite piece of music. The first impression in listening to my system from non audiophiles is how “clear” the music is and that has everything to do with proper bass integration and room correction. I can turn up the volume to concert levels and it doesn’t seem “loud.” Yet when watching a movie where a tank rolls by the ground shakes, your gut gets a strange felling and  stomach makes a flip just as you would if you were standing next to it; shots hit you in the chest and make you jump. 

I agree with you. I can talk all day about how important it is but hearing is believing. All of this is not that hard to set up either. I followed a tutorial on REW and made some measurements. Did another tutorial in MSO when I was learning and plugged in my own data after seeing how it worked using the tutorial files. Spent a day having fun adding and refining it. It’s so exciting to experience how big a difference is realized when room correction is done right with an integrated sub system. 

My last piece of my system will be BACCH for Mac. . . Saving up my coins now!  

Happy Listening,
Steve

Hello hifidreams,

     You're obviously well acquainted with the benefits of 4-sub dbas through personal experience. What exactly does your sub system consist of? 4 SVS SB-16 Ultras, a mini DSP with REW and a Multi Sub Optimizer?
     Your post makes me think of a couple other points worth mentioning:
1.  No one using a 4-sub dba, or anyone who has just personally experienced the excellent bass performance of a 4-sub dba for even a short demo, needs any further convincing of how amazingly well this concept works in practical terms, at this point you're just preaching to the choir. The icing on the cake is that it works equally well in virtually any room and the sota bass response integrates equally seamlessly with virtually any pair of main speakers.
2. Once you completely understand how well the dba concept works and you'd like to spread the word to others of this fact, I've discovered that writing or speaking about the virtues of dbas is likely the least effective means of convincing others since it sounds too good to be true and people remain skeptical. I think the most effective method is definitely just sitting down in a room with a decent dba system for a good audition. A good dba demo is worth at least 1,000 words
     I understand the skepticism about 4-sub dbas very well because I initially also thought it sounded too good to be true and I remained skeptical for many months before a free 30-day in-home trial period offer convinced me to give the AK Debra dba a try.
     I had dba skepticism because I had no experience with, or even knowledge of, the concept.  Now that I do, I've been transformed into a complete dba fan and promoter.

Tim,  
I made my secondary subs coffee tables :) An inch thick piece of glass in top with a lamp and no one even knows they are speakers, the WAF went way up at that point.

I agree with many above, four subs is the way to go, independently powered and signal driven through a mini DSP gives you flexibility to add room correction through room measurement via Room EQ Wizard (REW) in conjunction with Multi Sub Optimizer (MSO). My mains are passive subs running off of a Pass Labs X-250 and the secondary subs are SVS SB-16 Ultras which have their own amps built in. All are connected via balanced connections. The bass is accurate, powerful, and adds so much to music and movies. I add a little bass in my movie setting and had friends jump out of the couch a few times during a recent action movie. Pure fun. 
audiokinesis:

"If we agree with Duke's statement that 2 subs in a room provides twice the bass smoothness of 1 sub and 4 subs in a room provides twice the bass smoothness of 2 subs..."

I was paraphrasing my mentor, Earl Geddes.

Not only does the frequency response get smoother at a given location, but the frequency response variations from one location to another within the room also decrease (which follows from the first statement, but it may not be obvious).

Duke"


Hello Duke,

     So to paraphrase my mentor, you, not only does an AK Swarm/Debra or custom 4-sub distributed bass array system's bass sound approximately twice as smooth at a given location than using 2-subs at a given location, but the bass will sound smoother from one location to another within the room, too.  

     It was not initially obvious to me that smoother bass from one location to another within a given room follows from smoother bass at a given location within that room until you emphasized this. Based on my experiences using the AK Debra dba system within my own room, however, it was initially very obvious to me exactly how this bass smoothness manifested itself as sota bass performance not only at a given location within the room (my dedicated listening seat) but virtually my entire 23' x16' room.  

     I have 6 seating positions in my room: a leather recliner centered on the rear 16' wall which is my dedicated listening sweet spot seat, a leather couch with 3 individually reclining seating positions along the right 23' wall and 2 large chairs straddling a 6' x 8' window along the left 23' wall.  

     Of course, only my listening sweet spot seat is positioned for optimum stereo imaging and the other 5 seating positions have compromised stereo imaging of varying degrees.  But, based on my own evaluations and the enthusiastic and very positive non-professional reviews from multiple family members and friends, the bass performance at all 6  seating positions in my room  is perceived as state of the art for music and ht. 

      I've even informally evaluated the bass response at all of the non-seating areas of my room between my main front speakers/hdtv and the back wall, and was unable to find a single spot at which the bass was not equally and consistently excellent.   Perhaps you're thinking I'm too easily pleased or exaggerating, but I honestly can't think of of a single audible bass performance aspect that requires improvement.

     In the spirit of honesty, however, I believe I must make it clear there is a rather obvious and serious downside to using a dba system that has nothing to do with the virtually guaranteed excellent sound of the bass of these systems; it does require the use of 4 physical boxes in the room.  There's no dismissing or ignoring this fact that, in my experience on audio forums describing the sonic virtues of dbas, can often be a deal killer for many potential adopters.  

     I believe the subject of how to best accommodate 4 moderately sized wooden boxes (my AK Debra subs are 12x12x28 inches in size) in a domestic room environment is probably best addressed on a separate thread.  So I'll refrain from discussing this and just refer those to my system pics for those curious.

Tim

 "If we agree with Duke's statement that 2 subs in a room provides twice the bass smoothness of 1 sub and 4 subs in a room provides twice the bass smoothness of 2 subs..."

I was paraphrasing my mentor, Earl Geddes. 

Not only does the frequency response get smoother at a given location, but the frequency response variations from one location to another within the room also decrease (which follows from the first statement, but it may not be obvious). 

Duke

bstatmeister:
" I really only have 1 place it could fit while still having acceptable WAF - in the corner of the room just to the right of the right main. Hopefully, that position will suffice."
Hello bstatmeister,
     Placing a sub in a corner position usually results in a perceived bass boost in the room due to the close proximity of the 2 walls there that bass sound waves can reflect off. 
     The sub crawl is definitely the best method of attaining good bass response at your listening seat when utilizing only a single sub and room positioning options aren't so restricted.
     I'd suggest positioning the sub as many inches as possible away from directly in the corner, given your limited space,  will be less of a bass performance compromise.  You should be able to clearly notice that the bass will sound more natural and accurate in 1 of the 2 positions. 

 lordrootman:
" Your best bet to archive deep clean bass is missing subs together from 2-4 brand
im using SVS PC13 ultra with two klipsch SW-115
way better than using only one brand
also use both red and white outputs with Y adaptor  don’t use only LFE."

 Hello lordrootman,
       While there are no reasons mixing different sub brands or even sub types would be detrimental, there are also no reasons I'm aware of that mixing sub brands or even types would be beneficial.  Perhaps lordrootman could elaborate and enlighten us.

mijostyn:
" For all you people planning subs on a limited budget just buy the first one and add another when you can. For point source speakers 2 subs will get you 90% there. For you panel jockeys, Magnapans and electrostats you are going to have to shoot for 4."

Hello mijostyn,
      I think your idea, for people planning subs on a limited budget to just buy the first one and add another when they can, is a very good one.
      I believe a good approach would be buying the Dayton SA1000 1K watt class AB sub amp for about $300 and buying or building a single passive sub with a 10" or 12" aluminum long-throw driver, in a stiff cabinet that is either sealed or ported with plugs for optional sealing and about a 1sqft footprint.  This bass system could then be improved upon by adding up to 3 more subs as their budget allowed over time.  
       However, I disagree with your statement that using 2 subs with point source speakers will get you 90% of the bass response performance of using 4 subs in a dba system.  If we agree with Duke's statement that 2 subs in a room provides twice the bass smoothness of 1 sub and 4 subs in a room provides twice the bass smoothness of 2 subs, this would mathematically result in an accurate statement being that "using 2 subs with point source speakers will get you 50% of the bass response performance of using 4 subs in a dba system, not 90%.  
     I also agree with your statement of " For you panel jockeys, Magnapans and electrostats you are going to have to shoot for 4."  Planar magnetic speakers like Magnepans and electrostatic speakers like Martin Logans and Sound Labs are considered fast speakers that are notoriously difficult to seamlessly match subs with. Single or dual subs, especially those with 12 or 15 inch drivers, are just not capable of matching the speed of these fast speakers and, as a result, the bass seems to lag behind, be poorly integrated and sound disconnected to the fast and nimble qualities these speakers consistently display.  My experiences using Magnepan panels with the AK Debra dba system with 4 faster and more nimble 10" driver subs, is that there's a very seamless and quality to the reproduced sound that just seems like a very well integrated whole.

     

mijostyn:
"IMH experience the best performance comes from sealed, enclosed 12" subs Q @ 7 with Room control and a high powered class AB amp damping > 500, the higher the better. The only difficult variable is the enclosure itself which ideally should be infinitely stiff and heavy."

     I agree with you in general but I know excellent performance can also come from 4 ported 10" subs powered by a high powered class AB or class D amp with a damping factor >500.  The Debra/Swarm sub enclosures are very stiff and reasonably heavy.
     From my perspective, the primary reason for the sota  in-room bass response performance achieved through the use of dbas is still the fact that there are 4 fast and nimble subs producing bass sound waves from strategically varied positions in the room. 
      There are other important factors but having 4 well distributed sources of bass in any room is the crucial ingredient in creating this delicious psycho-acoustical cake. 
Tim
Yeah I bet it would. Which is why I did it. Details posted just now in my Tech article.

"I’ll take the stereo bass. It sounds better."

If you would be willing to list some recordings that do have true stereo bass, I would appreciate it very much.  I would really like to try some known-stereo-bass recordings on my system and see how they sound. 

What if you could get a realistic sense of immersion/envelopment from recordings that do not have true stereo bass, yet could easily adjust to take full advantage of true stereo bass, in about ten seconds?  Might that have some utility?

Duke

What are considered "bass frequencies"? Below what frequency are the L and R channels summed to mono? One way to hear differences between L and R is to use the Dynaco Quadaptor; it uses the difference (out-of-phase) content in a recording to produce a L minus R signal.
Exactly! I’ll take the stereo bass. It sounds better. It’s like compression. I realize engineers compress the life out of CDs these days. I don’t listen to compressed CDs. 

"I don’t believe that virtually all CDs have bass frequencies summed."

That’s okay. I didn’t either and argued with Earl about it. I forget the details of what he said but he had been sufficiently thorough in his investigation to change my mind.

It’s easy enough to do stereo bass anyway if you want to.

Duke


I don’t believe that virtually all CDs have bass frequencies summed. 

"I don’t believe it. No offense to you personally."

Could you clarify?  What exactly do you not believe? And, no offense to you personally either.


audiokinesis1,922 posts03-31-2019 1:00pm

"The Ford Motor Company?"

Ford hired Dr. Earl Geddes as a consultant. One of the questions he wanted to know the answer to was how common is it for CD's to have stereo bass content. He asked everyone in the department to bring in their CD's. After testing about a hundred CD's and not finding a single one with stereo content in the bass region, he stopped testing.  So no Ford did not test virtually all recordings, but the sample size was large enough for Earl to reliably conclude that stereo bass on CD's is quite rare.

Duke

>>>>>I don’t believe it. No offense to you personally.
noble100
Hello millercarbon,

    Congratulations on getting your custom 4-sub distributed bass array system built and operational! Are you planning on posting some kind of more extensive review of your dba results? How about a new thread devoted to how to build and deploy a custom dba?
    Using an Audio Kinesis Debra 4-sub dba myself for the past 4 yrs, I already knew your results would be spectacular but I think others really benefit by knowing how incredibly well this concept actually performs in virtually any room and with any pair of main speakers.
    If you're anything like me, you're going to find it hard to resist posting about the dba concept as the ideal bass system on the many threads consistently started by members looking for better bass response in their rooms and systems.
    However, I completely understand if you'd rather just enjoy your newly improved system for a few weeks, months, years or decades. The truth is that neither of us will ever need to buy another sub or bass system again.
    I'm just still amazed the dba concept isn't more widely known and used, especially on a high-end audio site like Audiogon. The fact that it's so difficult to overstate how well these dba systems actually perform, whether a complete $2,800 complete dba bass kit like my AK Debra or a custom dba system such as yours, I hope you agree we have an obligation to spread the word to our A'gon brethren and beyond.

Enjoy,
Tim


Thanks and yes, definitely will be writing it up, might even be posted today. Not sure but thinking best fit will be technical. Definitely agree this is a game-changer everyone needs to know about. No one should suffer the anguish of trying to perform the impossible, not to mention the sound of what people pass off as good simply because they don't know and never had a chance to hear. All it takes is a few minutes with a distributed bass array to know it leaves the conventional approach in the dust. I mean its so much better you truly cannot believe it until you try it, and then its just about the most obviously better thing you are likely ever to hear.

"The Ford Motor Company?"

Ford hired Dr. Earl Geddes as a consultant.  One of the questions he wanted to know the answer to was how common is it for CD's to have stereo bass content.  He asked everyone in the department to bring in their CD's.  After testing about a hundred CD's and not finding a single one with stereo content in the bass region, he stopped testing.  So no Ford did not test virtually all recordings, but the sample size was large enough for Earl to reliably conclude that stereo bass on CD's is quite rare. 

Duke


millercarbon The
Ford Motor Company did a study some years ago, to determine what exactly was needed for really good bass. What they found is that below something like 80 Hz the bass on virtually all recordings is mono.

>>>>>The Ford Motor Company? I want to believe them. But did they really listen to virtually all recordings? Maybe the study was back when everything was still mono. Besides, Be that as it may I’m not sure The Ford Motor Company has much audiophile street cred. 😁
Hello millercarbon,

     Congratulations on getting your custom 4-sub distributed bass array system built and operational!  Are you planning on posting some kind of more extensive review of your dba results? How about a new thread devoted to how to build and deploy a custom dba? 
     Using an Audio Kinesis Debra 4-sub dba myself for the past 4 yrs, I already knew your results would be spectacular but I think others really benefit by knowing how incredibly well this concept actually performs in virtually any room and with any pair of main speakers.
     If you're anything like me, you're going to find it hard to resist posting about the dba concept as the ideal bass system on the many threads consistently started by members looking for better bass response in their rooms and systems. 
    However, I completely understand if you'd rather just enjoy your newly improved system for a few weeks, months, years or decades.  The truth is that neither of us will ever need to buy another sub or bass system again. 
     I'm just still amazed the dba concept isn't more widely known and used, especially on a high-end audio site like Audiogon.  The fact that it's so difficult to overstate how well these dba systems actually perform, whether a complete $2,800 complete dba bass kit like my AK Debra or a custom dba system such as yours, I hope you agree we have an obligation to spread the word to our A'gon brethren and beyond.

Enjoy,
Tim 
The Ford Motor Company did a study some years ago, to determine what exactly was needed for really good bass. What they found is that below something like 80 Hz the bass on virtually all recordings is mono.

I just got my Swarm-based distributed bass array up and running last night and so I can now say from factual actual experience there is nothing else like it. If you want really good bass you will use FOUR subs distributed around the room. Period.
http://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/
Stereo bass? Vinyl mixes bass to a single channel for practical reasons. Moreover, localization of low bass is a non issue as you can't really tell where its coming from, only the higher harmonics is a clue, AND most music only have one bass instrument.
More subs is for other reasons, but stereophony it is not.
While most of this is true, the comment about vinyl is not. We don't mix bass at all when mastering. That is a technique used to reduce the time and cost of mastering time but its not something cast in concrete.
@vt4c, a timely reminder. Nice, just before someone suggested 8 or 16 subs!
You want two. Most subs have to cover a range from low bass, which is 'locatable' by a listener, to very low bass which isn't  and the power needed to produce a given spl is only 1/4 as much with a pair than it is with one.

Best test is to play a CD of organ music with low notes with no sub, then with one, and finally with two - makes a big difference and moves you, the room walls and anything in between.

You need pretty decent quality subs to integrate well with hi fi audio. The best bang for the buck I could find was the  VTF-15H MK2 DualDrive 
http://www.hsuresearch.com/products/vtf-15hmk2Dual.html
110 lbs each, 600 watt on board amps and they look pretty decent, not like something that got drop kicked off the back of the band's bus.
Your best bet to archive deep clean bass is missing subs together from 2-4 brand 
im using SVS PC13 ultra with two klipsch SW-115 
way better than using only one brand 
also use both red and white outputs with Y adaptor  don’t use only LFE 

https://www.amazon.com/Mediabridge-ULTRA-RCA-Y-Adapter-Feet/dp/B00KCQSW3E/ref=mp_s_a_1_11?crid=2ENEO...
Stereo bass? Vinyl mixes bass to a single channel for practical reasons. Moreover, localization of low bass is a non issue as you can't really tell where its coming from, only the higher harmonics is a clue, AND most music only have one bass instrument. 
More subs is for other reasons, but stereophony it is not.
Room aucoustics really need to be covered. Buy a measurement mike.
Use REW program, its free.

Oh, by the way I use dipole speakers with sealed subs and have absolutely no problem matching them up
I have made dipole subs using 6 drivers aside. They do not work. Even with huge amounts of power and room control you can not get 20 Hz out of them effectively. IMH experience the best performance comes from sealed, enclosed 12" subs Q @ 7 with Room control and a high powered class AB amp damping > 500, the higher the better. The only difficult variable is the enclosure itself which ideally should be infinitely stiff and heavy. 
For all you people planning subs on a limited budget just buy the first one and add another when you can. For point source speakers 2 subs will get you 90% there. For you panel jockeys, Magnapans and electrostats you are going to have to shoot for 4. 
   As far as my understanding of psychoacoustical bass principles and DBAs are concerned, I think of Duke as Mr. Miogi and he's showing me how to wax his car.


Mr Miyagi? Really? And after he said these are not the subs you are looking for?


I am probably gonna get a Rythmik F15HP after I get my Preamp situation squared away. Although I would love to buy 2 subs, alas, I cannot. I think I would rather buy one very big, powerful, tuneful sub than 2 smaller, weaker subs for the same amount of money. I assume I could get great sounding music from my 2-channel with 1 sub. Especially since I would only be using high level inputs and running the mains full range and only using the sub to fill in right around 40hz and below. I know that placement would be more important here, so I might do a sub crawl, but I am a bit nervous about it since I really only have 1 place it could fit while still having acceptable WAF - in the corner of the room just to the right of the right main. Hopefully, that position will suffice.

"Duke had told him OB/Dipole subs would be a better choice for use with his loudspeakers."

"when I told Duke what drivers I was going to use he said mine will kill his."

Okay that’s it. I’m firing my marketing department!!

Seriously thank you both, and thank you too Tim. I try to promote the distributed multisub concept when I post here rather than my specific product, but that distinction probably doesn’t always come across. My product is really just one possibly way of doing it. I would rather spread a good idea (which Earl Geddes developed and freely shared with me) than sell a lot of subs. (This isn’t as altruistic as it might sound - I have enough orders on the prosound side of my business to keep me busy full time.)

Nor is a distributed multisub system necessarily the most sensible approach for every situation.

If mijostyn takes my posts with a grain of salt, that’s fine. He has every right to be skeptical; I would be if our positions were reversed.

Duke

Hello bdp24,


     I'm not surprised at all that Duke displayed his knowledge and integrity when asked about open baffle dipole subs.  He's displayed to me the exact same vast knowledge of in-room bass sound wave behavior and the explanations of why/how 4-sub distributed bass arrays are such an effective solution with the exact same integrity.
     As far as my understanding of psychoacoustical bass principles and DBAs are concerned, I think of Duke as Mr. Miogi and he's showing me how to wax his car. 

Tim     
bdp24
Hey, when I told Duke what drivers I was going to use he said mine will kill his. How rare is THAT?!?!?!
I have been provided conclusive evidence of Duke's (audiokinesis) integrity. Due to my postings on the subject of OB/Dipole subs (particularly the one by GR Research/Rythmik Audio), I was contacted by an Audiogon member concerning their use with planar loudspeakers. I answered his questions, and a few days later received another email from the member, telling me Duke had told him OB/Dipole subs would be a better choice for use with his loudspeakers. How rare is THAT?!

Several posts above I wrote: "your four subs only approximate a line source; each sub still behaves as an omnidirectional point source."

Presumably in response, mijostyn wrote: "4 subs at 4 foot intervals with the outer two in corners does not approximate a linear array. It is most definitely a linear array up to 125 Hz or so."

Okay, but a line array is not a line source. A line array *approximates* a line source, which is what I said.

"If you review the acoustical properties of linear arrays you will note that they throw very little acoustic energy off their ends almost totally killing any refection off the side walls of the room

Imo their behavior at their ends isn't a potential issue; their behavior out in front of their ends (along the sidewalls, in this case) is a potential issue.

I know how to model line arrays. The spacing you used is not optimal. I can explain why if you are interested.  Because its propagation is not perfectly perpendicular to the line, your array will have increasing sidewall interaction with distance. I’m not saying that’s a fatal flaw, only that it happens.

"No other array does this in any dimension."

A planar array does this in two dimensions. In fact, I think a planar array would make more sense than a line array for your situation, given that your room doesn’t have a back wall (which imo offers you a unique opportunity). Again, I can explain if you are interested.

Duke

"The best you can hope to do in any enclosed space approximating a livable room is to control primary reflections and since they have the most energy that represents 90% of the battle."

I disagree with this statement as far as the bass region goes.

From a perceptual standpoint, speakers + room = a minimum phase system at low frequencies (according to Toole and Geddes and Welti, among others), which means that the ungated in-room frequency response is what matters. Focusing on the first reflections is at least paying attention to room interaction, but imo it’s not focusing on solving the problem that matters the most to the ears in the bass region.

"Putting subs all over the room simply creates more primary reflections."

Primary reflections in the bass region are not the primary problem that needs solving. But having many primary reflections contributes to solving the primary problem.

"... room control [EQ?] frequently has to correct troughs of up to 10 db and more..."

With a decent distributed bass array, you will not begin to have troughs of 10 dB or more. If your technique results in troughs of 10 dB or more then it is not solving the problems that matter. I don’t claim my customers will necessarily get plus or minus 3 dB in-room in the bass region, but many of them have reported that.

"Oh, by the way Duke, I am not trying to sell anything."

Okay. Maybe I’m missing something. How is that relevant? Please clarify because I don’t want to jump to conclusions.

Thanks.

Duke

Oh, by the way Duke, I am not trying to sell anything.
Audiokinesis, It always helps to know what ideal is to make the best compromise in any given situation. 4 subs at 4 foot intervals with the outer two in corners does not approximate a linear array. It is most definitely a linear array up to 125 Hz or so. If you review the acoustical properties of linear arrays you will note that they throw very little acoustic energy off their ends almost totally killing any refection off the side walls of the room. No other array does this in any dimension.  The best you can hope to do in any enclosed space approximating a livable room is to control primary reflections and since they have the most energy that represents 90% of the battle. Of course most people are stuck with a rear wall. My point is that all the room treatment in the world will not stop that reflection in the subwoofer region. The wavelengths are simply too long. Putting subs all over the room simply creates more primary reflections. For most people with normal rooms digital room control is the only way they stand a chance of getting flat bass at their listening position. The horizontal linear array minimizes the problem to a degree no other set up can and it increases efficiency at least 6 db requiring 1/4th the amplifier power which is critical with room control that frequently has to correct troughs of up to 10 db and more. This is why we need so much power when room correction is used particularly with small sealed woofers that have to force response below 40 Hz. The only other ways to achieve flat response at the listening position are to move the listening position to a point in the room where the bass is satisfactory or move the subwoofers around in the room in a trial and error way to accomplish same. Good luck. 
millercarbon,

     From what I’ve read about DBA systems, I believe your asymmetrical sub positioning/distribution plan will create more complex patterns of modal behavior in your room, resulting in decorrelation due to the smaller and more numerous bass peaks and dips present, which will be perceived as smooth, natural and seemingly effortless in-room bass response that is capable of reproducing fast, solid and taut bass just as accurately as deeper, more sudden and more powerful bass.
While I think you should get good results from your planned asymmetrical approach, I think it’s important you know that I’ve never actually tried this configuration with my subs in my room.
Just in case you’d like an alternative positioning plan that I know works, here’s how I positioned mine:


I removed my main speakers from the room, hooked up sub#1 and placed it at my normal listening seat position on its back, with the driver faced upwards.

I played some music with good and repetitive bass at a moderate volume and, beginning at the front right corner of my 23’x16’ room, I walked slowly across my front 16’ wall listening for the exact spot where the bass sounded best to me (the most natural and pitch accurate without being exaggerated or attenuated). I took my time and walked from right to left numerous times to verify the best spot. Once verified, I placed sub#1 at this exact spot with the driver facing, and less than 2 inches away from, the front 16’ wall.

I hooked up sub#2 in-series to sub#1 and placed sub#2 at my normal listening seat position on its back, with the driver again faced upwards. At this point, sub#1 and #2 are both active.

I played some music with good and repetitive bass again at a moderate volume and, beginning at sub#1 (now located about 2’ away from the front-right corner of my room along the 16’ front wall), I walked slowly across the remaining space along the front 16’ wall to the left front corner then turned left and continued walking from front to back along the left 23’ side wall of my room, listening again for the exact spot where the bass sounded best to me. Once verified, I placed sub#2 at this exact spot with the driver facing, and less than 2 inches away from, the front 16’ wall.
This completed the placement of both subs connected in-series to the first of the Dayton amp’s two sets of speaker outputs.

I continued this sequential sub positioning procedure for sub#3 and sub#4, with first sub#3 placed face up at my normal listening position and finally sub#4 just positioned at the exact spot I determined the bass sounded best with the first 3 subs playing the same musical content that had good and repetitive bass. This resulted in sub#3 sounding best along my left 23’ wall about 2’ away from the rear-left corner and sub#4 sounding best along my right 23’ wall also about 2’ away from the rear-right corner. So, subs #3 and #4 are located directly across from each other along opposite and parallel 23’ walls.

The results of this procedure in my room were so good that I never bothered to do the final procedure step of checking if the system sounded better with the phase reversed on one of the 4 subs as Duke and James Romeyn suggest.
I’ve been enjoying the excellent bass of the Debra bass system for almost 4 years now and I still haven’t felt the need to complete this step. The reasons are that I really have a difficult time imagining how the bass this system reproduces could be improved upon for music or ht and I really don’t want to jinx anything. If it’s not broken, don’t try to fix it, right?
Hopefully, Duke or James will chime in on their recommended DBA system setup methods and tips, too.

I’m looking forward to hearing your thoughts on your new custom DBA system.

Tim
millercarbon,

     Yes, you'll be amazed just how well it works. Have you given any thought about positioning your 4 subs in your room? If not, I can detail the process I used that worked out very well.

Let me know,
    Tim  


The one sub I have now was a nightmare to place. Because: one! With one you can move it around forever and never find the right place. I know. I tried. With four though....

From what I read they seem to work best distributed asymmetrically around the room. I'm thinking one front wall near the left corner, one right wall near the front corner but further from the front than the left one is from the side. Asymmetrical. Then one along the left wall further back than the sweet spot but not far enough back to be the same distance from the back corner as the front right is from the front corner. More asymmetry. Finally the right back one same deal, maybe a little further back than the one on the left. More asymmetry, more modes, more better.

As cool as it would be to play 3D asymmetry I think putting one up on a stand near the ceiling is aesthetically speaking a bridge too far.

I don't mind wire on the floor which is good because drilling holes is for me a tunnel too far. 
As I stated earlier I have 4 JL Audio F-113 Subs. The JL mic is placed at the listening position and I calibrate each sub individually. Then a little fine tuning with the DEQX for delay, gain, crossover, phase and crossover slope and then by ear.

ozzy

Editing timed out before I could fix one sentence; here’s how it should read:

"The array you described only tries to provide significant smoothing in one dimension, and it primarily does so at one end of the room (your four subs only approximate a line source; each sub still behaves as an omnidirectional point source).

Duke

"If you create a linear array very little energy disperses off the top and bottom or in this case to the side walls minimizing that interaction."

The array you described only tries to provide significant smoothing in one dimension, and it primarily does so at one end of the room (your four subs only approximate a line . The same number of subs arrayed differently can result in significant smoothing in two or even three dimensions (if you elevate one of the subs so that it’s closer to the ceiling than to the floor), and this smoothing will extend throughout the room.

"The only thing that really works here is just get rid of the back wall. I am fortunate in that I designed my media room without a back wall."

Relatively few people have that option. I have a hard enough time selling four subs without also requiring customers to remove their back wall! In other words, regardless of how well what you are doing works for you, it is not a generally-applicable solution.

"I am not sure if spreading other sub woofers around the room would minimize this or just create more complex patterns."

More complex patterns of modal behavior is how modal smoothing naturally occurs in a large room. The reason a large room has smoother (faster, better, more natural-sounding) bass than a small room is that the larger dimensions result in greater de-correlation of the in-room bass energy. Greater decorrelation = smaller and more numerous peaks and dips. A distributed multisub system mimics large-room modal behavior in a small room.

Duke

Audiokinesis, If you create a linear array very little energy disperses off the top and bottom or in this case to the side walls minimizing that interaction. Because the woofers are up against the front wall there is only the primary wave and no separate primary reflection off the front wall. So, you have eliminated three primary reflections. The reflections from the floor and ceiling are scattered in time. The reflection that will cause the most trouble is the one from the rear wall. The only thing that really works here is just get rid of the back wall. I am fortunate in that I designed my media room without a back wall. It just opens up into the rest of the house scattering the rear primary reflection. The end result is that the bass intensity is even throughout the room and much less equalization is required. If you can't get rid of the back wall you will be stuck with a degree of "comb filtering." I am not sure if spreading other sub woofers around the room would minimize this or just create more complex patterns. In reality it only really matters at the listening position.
The best bass is bass you can feel.
Positioning is one big key

See  yt videos by7 Acoustic Research