Why not have them built into the door panels. I have seen cars where the door pocket was modified and the part around the speaker enclosed.

Just a thought, but probably as much as trying to do kicks.

Alon

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'92 300CE - Sold
2004 C240 - 744 - C7 Wheels - Android Radio
2002 C320 - 816 - Sport Wagon - Sold
2006 E350 Wagon - 368 - Dead
2015 GL350 Bluetec - 197U