BMW E36 midbass

Hallo,

excuse me for speaking english here, I am from Belgium, and I have a really nasty problem for a long time already. I have a Boston Pro6.5 2-way 16.5cm component set in my 1996 E36 328i coupe, and the midrange element is mounted in the door in a special soundboard. The problem is that this gives me NO bass!!! I have been thinking for a long time now and I still don't know what's the problem. The doors now have been damped completely, the door panels are very strong, and I still have the same problem I have already experimented with a much cheaper DLS MS6 16.5cm midrange in small wooden sealed boxes, put them in the front of my car at my feet, and they really bump! I can also say that if I put the Boston midranges in these boxes the bass is much better too. But my doors (air between metal layers and door panels) now should be comparable with good strong sealed boxes because they are rigorously damped and fixed in place. Still I have almost no bass from them The amplifier or some other piece of elektronic can't be the problem because it's all set properly and it's all good quality material (Alpine amp)
My question is: do other people here have experienced the same problem in a BMW E36 coupe? I don't know what to do. My professional installer assured me the situation would get much better with dampening the doors and making a hole in the metal behind the speaker (to give it more volume), but now this has been done, I still have the same problem (so I should blame him actually, but I think I will be dropping that guy he knows' less about acoustics than me!).
The original BMW sound system had 13cm midranges at the kickpanels at the feet (hope you know what I mean) and they gave much more bass than I have know. Are the doors maybe a much worse location for bass than the kickpanels at the feet? This could be a good explanation, however I think this can't be true.
Greetings, and thanks,

Tim