"The AK swarm of four is typically run in mono."
This is because virtually all recordings have mono bass. Ford Motor Company wanted to find out how common stereo low bass was in deciding whether they needed stereo subs for their high-end sound systems. They tested hundreds of CD’s and did not find a single one with stereo below 100 Hz. Now they probable overlooked the few audiophile recordings that have stereo bass (which I’ve heard rumors of), but the point is, it is very rare.
That being said, there is some benefit to adding a second amplifier and running the Swarm in stereo or dual mono. The benefit comes from using the phase controls on the amps to put the two subs on the left side of the room 90 degrees apart from the two on the right side of the room. This is called "phase quadrature". The low-frequency phase difference at the left and right ears synthesizes hall ambience, and makes it sound more like you are immersed in a large acoustic space. Credit to David Griesinger for this technique. It also helps with the modal smoothing, so that you don’t need to reverse the polarity on any of the subs.
But you are correct, the normal configuration is mono, and when using a single amplifier in most cases the polarity of one of the four mono subs is reversed, which improves modal smoothing a bit. The main point of the Swarm is smoothing of the in-room bass, because "smooth" bass is "fast" bass. It is the (typically room-induced) peaks which decay slowly and make the bass sound slow.
Regarding the number of subs, as a general principle two subs are twice as smooth in-room as one, and four subs are twice as smooth as two, assuming the subs are intelligently distributed. Eight subs are grounds for a divorce, so I stopped at four.
Regarding the Dynastats, I’d be tempted to shove a pound or so of fluffed Polyfill into the cabinet, and then plug the port with an expandable plumber’s test plug, turning it into a sealed box. It will probably still go down to the upper 60’s or so, but my guess is that it will blend better with the sub(s) in sealed-box mode.
Duke
Swarm guy/former SoundLab dealer
