There has got to be something thats supposed to protect the inside of the door. If not, then that is a very poor design. While some speakers may be able to take a bit of moisture, you dont want water getting to the wiring in the doors for power locks, windows and so on. I would look into that further and find out whats to protect the inside of the door. There may be a inner skin that is inside the door, or something. I have never seen the guts of a matrix to know.