I noticed a hiss on certain songs coming from my passenger speaker in the door, so I I took off my door panel and sure enough the outer foam ring around my speaker was ripped. I used some 3M Fabric Adheasive spray that I had lying around from a Curtain Project. This spray glue reattached the foam to the outer wall. Now the speaker sounds great.

This fix could probably be used on the Sub-Woofer also.