I bought 4 subwoofers and I'm absolutely not doing a DBA! Hah!

Very nice!

Two woofers per enclosure would theoretically give you the option of using a force-cancelling configuration.   Depending on the enclosure width and motor depth, you might even be able to keep the same overall shape, though you would probably need to move the plate amp north so that its isolation chamber doesn't interfere with the woofers. 

@erik_squires, I should have specified that I was thinking of the woofers being side-firing (and therefore back-to-back), and now I understand that the woofer motors are too deep for that. 

I really like your idea of using the subwoofers as speaker stands, that’s a very efficient and elegant use of available floor space.  Ime in this sort of setup the imaging of the mains is improved by the use of spikes underneath the subs.  Even if you can only use one spike (like front-and-center), imo it makes a worthwhile improvement.

The only other (weird) configuration I can think of that might be worth considering is one woofer down-firing and the other front-firing.  Again you’d probably have to shift the plate amp northwards. 

Duke

@scotandholly, I’m pretty sure @erik_squires made his design choices with eyes wide open, and I respect them.  If you want to persuade him to go with a distributed multi-sub system, I guess you can try. 

(To avoid possible confusion I don’t use the initials "DBA" because they can also stand for "Double Bass Array", which is a very different approach.)

Duke

@kevn wrote: "duke, may I ask about your sense of things, all things room and equipment equal, if you feel that a distributed bass array will still give better bass accuracy, depth and cohesion with mids and highs than what erik is working on? Or is there too little known in his particular implementation to say? Thanks much : )"

In my opinion a distributed multisub system offers superior in-room bass smoothness and accuracy, and that over a wider listening area, compared with two subs located underneath the main speakers.  Either can of course be equalized, and either can be used with bass trapping.  In general the more bass sources located in acoustically dissimilar locations, the greater the net in-room smoothness.

Bass extension in a given room depends largely on the characteristics of the individual subs.  If we’re talking roughly equal dollar amounts, a single large sub will usually go deeper than multiple smaller subs.

"Cohesion with mids and highs" is largely a system-integration issue, but @erik_squires’s approach of locating the subs beneath the main speakers allows him to use a higher crossover frequency and/or gentler crossover slopes than a distributed multisub system can get away with.   So Erik can cross over at 300 Hz if that turns out to give him the best results.

We are all constrained in some ways in what we can actually do, so we optimize within those constraints.  I’m quite confident @erik_squires has made fully informed choices to get the best results (acoustically and aesthetically) given his priorities and constraints. 

A few years ago at T.H.E. Show in Long Beach I showed a system which had subwoofers build into the speaker stands.  The woofer itself was angled at 45 degrees to reduce the force vector in the horizontal plane and thereby reduce rocking.  So despite my preference for a distributed multisub system when such is practical, I’ve also done something conceptually somewhat similar to what erik is doing. 

Duke

@clio09 wrote:  "I recall hearing that system in Long Beach and liked the concept. I might like to try something like that. If you don’t mind sharing, what were the dimensions of the cabinet that was used in the set-up?"

The Long Beach version of the "SuperStand" was about 24" tall by 12" wide by 15" deep, base included in the height dimension but not in the others. The footprint of the base was 18" square.  Some of the internal volume was devoted to an up-and-rear firing 10" coaxial driver, and some of the internal volume implied by the outer dimensions was lost to a large "notch" in the back, with the woofer mounted on the upper surface of the notch and the coaxial mounted on the lower surface of the notch.  The woofer was in a sealed enclosure.

The speaker atop the SuperStand was 23" tall by 12" wide by 12" deep.

Link with photos in case anyone wants to see what we’re talking about; scroll down a bit for photo showing the notch:

New gear from AudioKinesis and Resonessence Labs | T.H.E. SHOW 2019 - pt.AUDIO

Duke