problem with logitech 440 speakers

[joker12578]

Got these a few months ago, the sub has from the start something I can only call speaker rattle. Couple of friends told me this is normal, but I find it hard to believe when your base lvl is around 50% this is normal. Today I wanted to test it out, so turned up the bass all the way and the sound to about 50%. Never had this happen before but the sound goes from loud to low like someone is turning it down.

Anyone have this problem before or know what might be the problem? thanks for any information.

EDIT: forgot to say I have Creative CA20K1 X-Fi Xtreme Fidelity Audio Processor

[joker12578]

I think I have found the problem for some reason it's has started setting off GOMs normalizer. It hasn't done this before, well anyone have any ideas on the rattle then, could this also be because of the normalizer? Thx