Help me understand "the swarm" in the broader audiophile world

brownsfan:
" For those of you using DBA combined with room treatments, did you find that the DBA reduced ringing substantially without room treatments, or should I expect my Swarm to primarily rectify nulls at the MLP and expect that the traps will be required to achieve good decay times?"

 noble100:  My negative experiences with decay times in my room and system actually occurred prior to even using a DBA and concerned the opposite of ringing, which was the truncation of decay times.   I've noticed this unnatural and premature cutoff of normal note decay times on both my former pair of Magnepan 2.7QR main speakers, driven by a stereo class D amp, and a pair of 12" subs with built-in class D amps. 
     I'm fairly certain the cause in both cases was the extremely high damping factors characteristic of class D amps in general, which are typically rated in the low thousands as opposed to usually being rated in the low hundreds for class AB amps. 
     The higher the damping factor, the more firmly an amp has control over the starting and stopping of drivers, in my former case the large 623 sq.in. planar-magnetic bass section in each of my former 2.7QR speakers and the 12" dynamic cone woofer drivers in each of my former self-amplified subs.
     Since replacing my dual self amplified subs 4 yrs ago, with the AK 4-sub Debra DBA powered by a 1K watt class AB amp, I've definitely noticed the bass note decay times are somewhat longer, more accurate and more natural with a total lack of truncation or ringing.   I've never experienced boominess or ringing with my DBA, either with zero bass room treatments prior or extensive bass room treatments currently. I seriously doubt you will experience any negative bass performance issues in your room, either.
     

brownsfan:
" I guess my plan would be to remove room treatments and optimize the bass response without room treatment, then add back the bass traps judiciously to further improve frequency response and ringing.  BTW, mains are down 3 dB at 27 Hz, but I have decent response down to 20Hz or so.  Is that a reasonable approach?"

noble100:  It's an approach, but I really don't believe it's necessary.  When I installed extensive room treatments in my room, I just made sure that none of the subs were firing directly into a wall or corner bass trap, ensuring each had at least a small section of bare wall to launch their bass sound waves into and not being in very close proximity to a bass trap.  This produced very good results in my room.
     Your mains already have fairly deep rated bass extension.  I think it would be more beneficial for you to pay close attention to the volume and crossover frequency control settings on your subs, as well as the slopes of the subs' crossover filters.
     Are you planning on using an AK Swarm or Debra complete kit DBA or creating a custom 4-sub DBA using self-amplified subs?   I can better tailor my advice knowing the details.

brownsfan:
" Finally, I've read about the crawl approach to optimal placement on the Audiokinesis site, but I'm thinking of using REW to supplement what I hear.  Anyone find REW useful in Swarm sub placement? "

noble100:  I sequentially and optimally positioned each of my AK Debra subs utilizing the crawl method.  I've never used REW or any room correction software/hardware, room analysis or mics but I do recognize their usefulness. 
     My best advice would be to first locate each sub using the crawl method and then utilize REW to further fine tune and verify optimum positioning.  Ideally, they'll result in the same position but, if not, it'll be at your discretion.

Best wishes,
   Tim
      

@noble100  
Always a +1!

+1 also to millercarbon for his advocacy in addressing the simple, inexpensive (and at times free) tweaks that most of us tend to ignore.  
I would just add for those out there attempting the sub elevation route to do the crawl method for any subs on the floor first.

In my 9' ceiling 14' x 16' room, I varied elevation of the two ceiling facing subs as a simplified "vertical crawl" method.

Latest interesting experiment has been angling the ceiling facing subs to 45 degrees relative to the ceiling.  

Not sure if this is an accurate description but it seems to have further evened out the tonal balance across the mid to lower frequency range.

There is a bit more realism as well in holographics and venue specific acoustics.  

Also apparent is an increase in sharpness (clarity?) in terms of  instrument location and soundstage height.

Lower midrange to low presence ringing that I noticed before are now significantly reduced.

Working on a ceiling mounted subwoofer isolation system that will allow horizontal and limited vertical placement in any direction.

Hanging 2 or more subs from the ceiling would likely exploit the possible sub placements in a truly 3D manner.

@noble100 ,  Thanks for your helpful comments Tim.  In answer to your question, I have ordered a Swarm system.

Interesting comments on your experience with decay times.  In my case, REW shows the frequencies at which ringing is observed correspond to peaks in the frequency response curves, so I am pretty sure that these aberrations are due to room modes and not equipment.  I've got 3 GIK soffit traps, 3 RealTraps Mondo Traps, and 2 GIK Mega traps in the room, and these did a pretty good job of mitigating modal ringing.  What ringing remains is at a very low frequency where trapping struggles.  I've also got some speaker cabinet resonance adding to the delayed decay at the lowest frequencies. 

My thinking on removing the room treatments is that I will likely want to have one sub in a corner, and all of the corners are treated.  None of my corner treatments are permanently installed, so removal will be trivial, and doing so will allow me to select the best corner for placement of one sub.  

My room is dedicated, and I have almost complete freedom to place all 4 subs in all three dimensions. 

@millercarbon --

...  since we all know no one or two subs can ever touch a DBA, then not only do the high-end dealers make money selling you the one sub that can’t work, they get to sell you another. And another. And another. And EQ. And more amps. And room treatments.

There’s simply way more money to be made selling audiophiles things that don’t work than things that do.

Especially if they first sell you on a good story. Which since you already know DBA works, and yet is not widely adopted, then you know how good they are at selling audiophiles on stories.

And that’s the real answer to your question. Why would anyone buy a sub? They don’t. They buy a story.

This is actually an excellent summation, if it weren't for the fact that a pair of subs can work wonders in a more limited number of seating areas. Really, why would you want smooth response most everywhere in the listening room when where you're seated is where you're seated, positioned most likely dead center in front of your main speakers and you're less than a goddamn convention of people? Yes yes, sans DSP and room treatment and what not and just close to an acoustical miracle left for you to savor relatively cheaply, but still; a pair of (not least bigger) subs can do great as well, and not only to the ears of some stubborn dumb asses that don't know any better. I have listened to DBA set-ups, not SWARM's per se but a variety of quad sub systems of greatly different sizes all from 8" DR woofers to 15"-loaded horn subs systems. By far the latter was the best, indeed some of if not the best I've ever heard/felt, but without a shred of a doubt I preferred dual sub set-ups with 2 x 18" ported DR woofers and even more so 15"-loaded tapped horns (from the pro arena), both placed symmetrically to the mains and crossed no lower than 80Hz, compared to asymmetrically placed DBA's with up to 12" DR sealed woofers and crossed somewhat lower.

I, indeed we don't know any better? Excuse me, but that would be plain arrogant, or, better yet: ignorant to presume. You're placing yourself on top of a pedestal taking a piss at what you haven't experienced, or if you have it wasn't your cup of tea (to each their own, perhaps?) - fair enough. However, this never gets through, and instead it's the same condescending diatribe again and again against anytime other or LESS (to your mind) than a DBA.

You guys love selling the DBA approach, but if bass quality and integration is anything to go by it seems I should be even more prolific with the traits of a pair of big, efficient, symmetrically placed and crossed-no-lower-than-80Hz subs. That's something to savor as well, but the same could, to a perhaps even higher degree than the audiophile resilience to DBA, be leveled: who cares?  

Let's be clear: what you're getting at is, essentially, spot on. The physics part of subs integration with a DBA gets annoyingly in the way of the audiophile snooty approach that loves what's more expensive is also necessarily better. It's hilarious as it is sad. 

Mine is not likely typical. I tried to integrate subwoofers with Magnepan 0.7's and the subwoofer or pair of them always call attention to themselves without integrating into Magnepans. I wanted a more full bodied bass and I now use a pair of DWM's. My amplifier output transformers have taps at ground (for safety because the tubes run at 1 kV) 4 Ohms to which I connect the 0.7 : negative to ground and positive to the 4 Ohm tap, and the DWM "woofer" elements connected negative of one of them to the 8 Ohm tap, positive of said element to negative element of the second element of the same DWM (two 4 Ohm elements in series) and positive of the second element to the 16 Ohm tap. If you use an SET to work with Magnepans it takes an AM radio station transmitter tube such as an 833A.But I have heard subwoofers demonstrated at a high end store with dynamic element speakers and they improved the sense of image. My guess is a swarm might work with dynamic cone speakers.