is the subwoofer plugged into an outlet on the same AC circuit as the other components? It also can be a result of other equipment in the mix, for ex., direct tv receiver.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85