Dell WL6000 Computer Speakers "centre speaker crackles" Questions

...even when the pc is turned off and the speakers are left plugged in. It seems to be coming from the centre one under the moniter, I've had them for just over 1 year. Are they mendable or do I go out ...

centre speaker (which ur suppose to) the centre speaker acts as a "link" to the left n right channels some sound cards have a function call "stereo expander" or something like that and will play sound