I had mine off this past summer and it looked like there was quite a bit if you put the speakers at the ery front of the door (where the concert system mounts). I remember thinking mounting was more "diameter" limited than depth limited.
Brent
I just took my door panels off this weekend to put in my MB DSD 213. There is a basket like setup the speaker goes in (concert sound) That makes the speaker sit flat on the door ( the area were the concert sound goes is not flat) That basket is 2 1/4 deep I have to cut the bottom out to make it fit MB 2 3/8 deep.If the magnet dia. was much bigger it would of hit the window motor