I use 3 subs, not 4 because I'm cheap. And they're not matching. Two are PreSonus Temblor T10, 10 inch ported professional subs, 20-200 Hz. The third is a CSS 10 inch sealed mid-bass sub using XBL2 woofer and SD300 amp, Fs=26 Hz. The main speakers were commissioned, the driver Fs = 30 Hz, so I have 5 bass sources down to 30 Hz. The audio room is 8ft x 13ft x 21ft, well insulated, and has (10) GIK 244 panels plus (3) tall randomly filled bookcases on the side walls. The subs are connected to two sub low voltage outputs on my NAD M10, with both outputs split between the CSS sub and one of the T10 subs. Subs are located near room corners and in phase.
The room without subs/absorption has 15 and 18 dB peaks at 53 and 82 Hz as predicted by the primary room dimensions and the speed of sound. With subs/absorption the peaks have been reduced to 5 dB. Note that adding Dirac flattened the response but was deemed undesirable (a good audio friend thought it was "to aggressive"). Perhaps it was the impulse or other parameters being adjusted that negatively affected the sound.
Don't recall how the miniDSP system works. Dirac is simple; just specify none, one, or two subs (I specified two since I was using both sub outputs); take 9 measurements in/around the listening chair (sofa option made very little difference); and it generates a recommended "curve" which you can manipulate and save.
The concept is to distribute bass production. 4 subs would theoretically be better than 3, but the effect should be similar. Again note that the main speakers may or may not contribute the number of bass sources. Suggest reading Floyd Toole's "Sound Reproduction" 3rd edition to learn how speakers behave in-room. In-room bass performance has nothing to do with music versus HT or one versus many listeners. But as HT has to do with "special effects" exaggerated bass that might be desired would be lost if "properly" set up.
Both referenced products should work well, but hardly fit into what I deem to be affordable systems. Heard the swarm briefly at Axpona but can't give an opinion. They were tiny compared to LeJeune's main speakers and what most think of bass versus mid/treble production. Duke has the swarm subs designed to augment room gain.
