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

Rix, I would forget about open baffle subwoofers. Hold on to your opposed driver balanced force design. Work on creating a very stiff, heavy enclosure design of the right size to support the two drivers. What is the stiffest enclosure shape you could use? If you have more or less advanced woodworking capabilities give me a shout and we can discuss it:)

@mijostyn -
I have full access to a cabinet making shop. I've been splitting planks on a band saw, running them through a thickness planer (before and after), joining the solid cherry wood (often with a biscuit joiner). Attempting to build four units from AcousticFields QRD 17 diffusers plans. I have only just managed to get the materials list for the diffusers, and I am going to have to let my friend program the CNC so I can get table time to cut the panels for assembly. I have some skills, always learning more.

I worked for a loudspeaker designer, my system page has photos of my current two pairs of speakers during glue up. I'm probably not going to do steel lined sub woofer enclosures though (so far the most rigid enclosure I have made is high density fiber board, 1.6 times denser than MDF, laminated to steel plate). My larger stand mounts are in the high 90lbs each. Stiffest enclosure shape might actually be a tube with baffles on the ends, not the most practical of shapes though without creating a stand of sorts.

I have a Tympnay LAT, it was controlled by a DSP, and I have to say I love the sound and without vibrations. Personal taste obviously, I was hoping a slot loaded W frame would do similar to the LAT.

The more I read, the more I want to both elevate and maybe try more subs as well.

Sorry I went off SWARM topic, but today whilst trudging through a quagmire I was considering the GIK bass traps and not affecting the SWARM sound.
I wondered if it was possible the bass traps simply didn't have the absorption (grunt) power to transform the energy from the subs, though enough to deal with the midbass??

From what I have been reading, and researching, the claims are by many that low frequency waves are very challenging and often traditional fiberglass traps simply don't have the power to deal with them as well as other frequencies.

Speculation of course.

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.