dpocs

My subwoofer (KSW-10) with the quintet system likes to turn itself on to a dull humm in the middle of the night.?!?!? WHY?!?!? I't started after it kind of popped and hummed while listening to Car Talk one Saturday morning. After turning it off and back on, it seems to still work fine. Have done the testing with DVD tests, and it works. Sent it to the shop for repair, and they found nothing wrong. What's going on?!?! it's connected with the single LFE cord. (i'm not too technically inclined)