Dynamat original is crap. It doesn't conform to contours very well and even with proper heating during installation, I've had trouble getting it to stay (it peels off after a while). Although for doing a large flat area such as a floor I guess it would work fairly well. Just be sure to do this in the summer when you can go with your windows down for a while to help get rid of the horrible asphault smell. Dynamat extreme is great, but too freakin expensive. It conforms to curves very well and sticks great. Once this stuff is on, its not coming off. My recomendation though is to go to Lowes or Home Depot or some similar store and get some roofing insulation (forget what its called but it is almost exactly like dynamat extreme). A friend of mine bought 100 sq. ft of some no name dynamat extreme wannabe off ebay and when it came in the mail, it was just a roll of roofing insulation. He was very dissapointed at first but after looking at it, it really was almost exactly the same as dynamat extreme. Really sticky black rubbery stuff with the thin aluminum layer on one side. He went ahead and installed it and it worked great. He just wishes he knew about it before he ordered it from ebay because it would have been a lot cheaper just to buy it directly from a store instead of from some punk kid who marked it up, called it something differen't and put it on ebay.

I have dynamat extreme on both front doors and in my trunk. I mainly did it to stop some of the rattling that was happening at higher volumes. It completely got rid of any rattling I had. And suprisingly, even just doing the front doors cut down on some road noise. It also made my music sound more crisp. When the speaker pushes the cone out, it also pushes the door its mounted to back (for every action there is an equal and opposite reaction blah blah blah...). And when the cone is pulled back it pushes the door in. Adding the extra mass to the door resists this and made my music sound much more clear. On some of the more solidly built cars, it probably wouldn't make as much of a difference. But on my little sentra, the door panels are extremely thin and flimsy and it helped a lot.