Just moved into a new house. Sub was moved in original box/packing, and I took meticulous care. The UPS says my wall outlet is grounded, no faults. But when someone turns on a light somewhere in the house, a loud, constant hum usually suddenly eminates from the sub. Using the hammer methodology (slapping the side) silences the hum...and all seems well, movies sound fine, etc, until another light is turned on. My old house didn't have a grounded outlet for the sub (most was still old knob-n-tube), but I never experienced this, except when I had the sub right next to the sound system, which WAS on a grounded outlet (romex)...so for the last five years, I had the sub on the other side of the living room, and everything was fine. But in this new house, I kinda have to have the sub near the sound system, using the same outlet. Any ideas of what's wrong? If you need additional config info, lemme know. One thing to point out that may be of interest is that many lights are controlled by reostats.