I recently installed two 6.5" pioneer speakers in my doors and encountered a problem even from my last car.... the door is rattling.
when the music is turned up (especially bass and lower tones) the rattling in my door becomes unbearable.

anyone know of solutions to insulate or muffle the sound of this?

 

search sound deading there is also info in the FAQ sticky

 

I get the same thing. I think its how the door is made. Probably some wires or something rattling around.