I has something really odd with my SVS that happened years ago.
Randomly, and after months of not having any issues, it would randomly go into what I am calling "full power, deep bass" mode. Completely random and freaked us out even when it was during the day. I even would unplug the source cable, and it would still do it. I plugged it in to a different outlet, and a different circuit, and it would still do it.
SVS sent me a new amp, but that did it too. So I just couldn't figure it out. I replaced the amp, I changed the electrical source, and I removed all input...
What ended up fixing it was when I put a small surge protector just for the subwoofer in place. The problem stopped and never came back.
My best guess was that some sort of interference was coming through the power line and telling the sub to "wake up" and play the super loud and low sound that was filtered out with the surge protector, but that is just speculation. I have since moved and never had the problem with or without a surge protector.
Just something to try (the surge protector). Keep in mind that a power strip is NOT a surge protector. One will cost you as low as $3 and no nothing but add outlets, the other will actually have some sort of Joules rating on it.
