There's a lot more bass in a 6.5" driver than most of you think

@erik_squires apologies if you have mentioned it. back to your original post. I wonder how big is your room? 6.5" may be good enough for a medium room, but might be a bit lacking if there isn't enough travel to move enough air to energize a large room.

     The standard procedure for installing a 4-sub DBA system such as the AK Swarm, includes the final step of inverting the phase (simply by reversing the pos. and neg. connections on the sub) on each of the 4 subs sequentially to determine if any individual sub's phase inversion positively effects the overall bass performance in the room of the 4-sub DBA system as a whole.  
       In my 23'x16'x8' room, currently without any bass room treatments and without the use of any DSP or electronic room control/equalization of any type, I noticed no improvements in the overall bass performance in my room of inverting the phase on any of the 4 individual subs comprising my 4-sub AK Debra DBA system.  
      However, this does not mean that phase inversion on a particular individual sub in other 4-sub DBA systems would not be significantly improved in overall bass performance. I believe only a brief audition of a good quality 4-sub DBA system would be sufficient to convince the most ardent skeptic of this concept's near state of the art effectiveness.
      I have no stake in this concept except the $3K I spent to adopt it, my intention is solely to spread the word of how amazingly well it worked for me and will work for anyone else guaranteed, regardless of room or main speakers utilized.

Tim

@jmpsmash

apologies if you have mentioned it. back to your original post. I wonder how big is your room?

The total acoustic space is about 12.5’ x 30’, divided lengthwise into a living room and a second kitchen/dining area.

6.5" may be good enough for a medium room, but might be a bit lacking if there isn’t enough travel to move enough air to energize a large room.

So, again, the point of the post is not that everyone will be satisfied with a small woofer, but to help buyers understand that even relatively small speakers can put out quite a bit, and that room acoustics matter a great deal. For my modest apartment, with the couch 9’ or so from the speakers this is plenty of high quality bass.  Which brings me to another point:

Good room treatment can make speakers sound BIGGER. Going with larger speakers in a bad room may in fact be a bad idiea.

@erik_squires

"

To appreciate what constitutes a good bass, one needs to experience a distributed subs system like the Swarm

Not at all universally agreed to.
https://www.soundandvision.com/content/are-you-putting-subwoofers-behind-viewer "

The author has no idea how distributed bass works. Both Geddes (PhD thesis on bass) and Welti (Floyd Toole’s Harman lab) found in their research that key to distributed bass is asymmetric placement. Geddes believes three sources is enough: one in the corner, two others haphazardly against other walls. Duke LeJeune, Geddes’s coworker and constructor of the Swarm, adds the fourth source. There is no point adding more sources. Phase switching is not really part of the concept. Digital corrections of the whole system can be applied, but already the haphazard placement does most of the job. Digital corrections using counterwaves, such as those used in Kii3 or D&D, don’t really work below 50-60 Hertz. To battle complex phenomena like room modes, randomness is the most optimal way. Here, one can see easily, what problem room modes can be computationally:
hunecke.de | Room Eigenmodes Calculator

One more interesting concept is dipole bass, proposed by Siegfried Linkwitz in his  LX521. The subs are v-frame dipoles and the side wall modes are minimized by cancellations. The bass is incredibly clear and tight.
Finally, one can put the single sub next to his listening position to get at least one good spot with it.