Boom Mat 6"x9" Speaker Baffles
Crutchfield Customer Review (What's this?)
easy to use. Probably better than infinite baffle of trunk or door. Had to cut a port to allow woofer to breathe. Bass much better with about a two inch port.
Pros: keeps speaker clean and dry. Not convinced of any sound improvement.
Cons: Had to cut port for woofer. No guidelines for port size or location.