Hello, I have a PSB 5i subwoofer in my theater and just recently it started to make static and crackling sounds. It won't make the crackling when there are only small bass sounds like firing a gun in a video game, but if a big explosion happens instead of projecting louder bass, it just starts crackling. It has been working fine for 3 or so years and has never done this before. The volume on the sub is only at about 40% and I checked all the wiring and the connections seem to be ok. Any ideas?