its your input source i bet, not the sub... but that doesn't mean it can't be good on your sub.

I know the dsp in the 500 basically won't allow harmful signals to pass to the driver and I would assume the 350 is the same way. It, very eloquently, will trim back the signal instead of just clipping it.

I have had times when my input source gets a bit scrambled (digital decoding) and a bunch of loud and unpleasant noise outputs a high volume... that may be your problem also.