door problem?

when I close my back door, it closes with a nice appealing solid 'clunk', but my front door sounds totally different. if I close it hard enough, it sounds HOLLOW. also, the door vibrates a lot when bass is heavy. is there something wrong? do I just need to have the damn thing covered in dynamat?

I have a 95 Jetta, and I get different sounds from my doors as well when I close them. The passenger side sounds like something is no longer attached inside.
As far as the bass rattling, I have had that since the day I bought the car. I don't even bother turning the bass up. It sounds like all the plastic on all the doors is loose. Cheap crap.

check the panel those clips that hold them on are p.o.s. my car they broke about 6 times in the last 3months but when they were broken they made a clapping sound and poping and rattling so check that out

well they don't RATTLE they just vibrate really bad...like my sideview mirrors go crazy. I want to put better speakers in my car, but I don't want to end up shaking my door apart (especially since I hear MK4's are notorious for windows falling in)...do you guys think getting dynamat put on the door would help the vibrations lessen?