Yes, the Dayton is not operating correctly if there's a thump, buzz or hum. With my AK Debra, I found the overall bass sounded boosted if any of the subs were positioned within about 2 feet of a corner. It won't harm anything even if you put a sub in each corner. I just prefer my bass powerful, dynamic, smooth, fast, accurate, detailed and natural without overemphasis.
I tried wiring 1 of the subs in reverse polarity as the procedures suggest, one at a time, but without noticing a positive effect. I run all of mine in-phase and ported. My goal was to set the level and crossover frequency both as low as possible with the bass still sounding powerful, smooth, detailed and natural to me. My main speakers only have a rated bass extension of 35 Hz so I run them full range with the Dayton's level set at about 11:00 (slightly below half volume) and the crossover set at 40 Hz.
This results in the deep bass being perceived as seamlessly blended or integrated with my main speakers but the bass is still very powerful, dynamic, natural that can even be a bit startling on music and HT when the source content dictates for sudden powerful bass reproduction.
Welcome to the DBA club, dnicol, have you paid your yearly dues yet?
Best wishes,
Tim