Audio Systems: subwoofer trouble, sandpaper, thump

Question
no matter what button i push, or even when the tracks change, my subwoofer thumps really loud. it is a powered sony and the receiver is kenwood.

Answer
This is usually caused by a poor ground wire; either the connection itself or the place it is grounded at.  

Make sure the ground is solid; remove the ground and sandpaper it down so the ground wire is making good solid connection to metal.

You may have to take the ground wire all the way back to battery. Have you tried that?

And, try this: Just remove the input to the sub amp and see if the thump clears.  If so, in this case, the grounding of the head unit may be the problem.

Let me know more.
c