I asked around at various pro audio shops and there seems to be alot of various opinions about Dynamat. Some say that it is really good but takes time to apply correctly, others say that is costs too much and unless you do the floor area with a leaded mat it doesn't really do much help.

One shop told me about Deflex pads to glue on to the flat surface behind each of the door speakers.
http://www.deflex.co.uk/cgi-bin/defl...deflexshop.cgi

Deflex Acoustic Panels have excellent performance characteristics. Made from an advanced polymer to reduce unwanted cabinet distortions to an absolute minimum. Deflex Panels control the energy, not absorb it, thus enhancing the performance of the the system.

I tried it in my doors and it seemed to help the little 5.25" woofer do a better job than it did before adding an amp.
Before I had minimal bass and now I have moderate bass. Cost was about $45 retail plus installation. Need to glue on a gel disc about 8 inches in diameter to the door panel which is parallel to and behind the speaker's magnet. Doesn't install if there are obstructions in the door or the surface is not flat. Can't cut or alter the disc.

A list of reviews from 1994 (old news!)
http://www.deflex.co.uk/cgi-bin/defl...deflexshop.cgi

Can purchase at cascade audio
http://216.239.33.100/search?q=cache...n&ie=UTF-8
Ohh -got some bass now- I can feel it