Creative Labs Gigaworks S750 Computer Speakers "weak subwoofer sounds" Questions

Subwoofer crakling sound when playing anything. Here's the deal. Everything powers up, but when i raise the volume, the sub start producing a cracking sound and if a raise the volume real hi the sub ...

...subwoofer on dell computer since 6/2003. great sound, really rocked the place. until a more than a few months ago, when they just quit 'putting out". sound is very weak, even when volume on computer ...