I just stuffed a metric buttload of dynamat in my zippymobile: from the bottom of the folding rear seat all the way back, with two layers in places, and large squares inside the doors and behind all speakers and under the carpeting in the front. Aside from the doors sounding different when they close the noise level is only slightly reduced. Did I do something wrong here? Did I fail clean the srufaces well enough? The car is a Y2K WS6 Trans AM.

I had a friend who did the same thing. Admittedly, it was a Celica instead of a trans-am and probably benefited more from the procedure. Still, after he was done, he said that it was a lot more trouble than it was worth. It did reduce the amount of road noise in the car, but not enough to make it worth all the effort of installing the stuff.

The problem is that most modern cars are already noise proofed pretty well, and an extra layer of rubber won't change much.

I've always said that you get more value out of more powerful amps/speakers/subwoofers than you do out of dynamat.

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Tony Fabris

The problem is that most modern cars are already noise proofed pretty well

I may well be incorrect here, but I was under the impression that DynaMat was meant to dampen resonances and harmonicscaused by the speakers themselves (for instance, when installed in doors), not to insulate the interior of the car from outside noise.

Somebody please feel free to correct me if I am mistaken.

tanstaafl.

"There Ain't No Such Thing As A Free Lunch"

Dynamat is a dampening material. Cars come stock from the factory with dampening material. For example, luxury cars have hundreds of pounds of dampening material to dampen everything from road noise to engine noise. So if you had a bell hanging on a string, and you tapped it, it will resonate. If you dragged the bell along the ground, it will resonate. If you put a small strip of dynamat on the bell and tap it, it will resonate but only briefly. If you dragged the bell along the ground it won't sound as loud. That's the idea. The more dynamat the better. The thing is that dynamat is so much heavier and "damper" than the original stock stuff, you need to invest dynamat onto every surface of the car to get benefits. You have to cover every inch!! :)

Calvin

Calvin

I may well be incorrect here, but I was under the impression that DynaMat was meant to dampen resonances and harmonics caused by the speakers themselves (for instance, when installed in doors), not to insulate the interior of the car from outside noise.

The ads for the stuff in the Crutchfield catalog advertise both of those characteristics as being benefits. They sell either pre-cut pieces for just your door panels, or huge sheets of the stuff for covering the firewall, floors, ceiling, etc. They even have a cute little illustation showing the "noise floor" of the car both with and without dynamat, so the latter usage is definitely one of their selling points.

Whether or not it's effective at either task is a subjective judgement. I was impressed with the difference it made in my friends' Celica, but he says it wasn't a large difference and wasn't worth the extreme effort required to install it under all his door/wall/floor/ceiling panels.

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Tony Fabris

I'm not sure the "Cover everything" approach is necessarily the best; it will definitely turn out to be the most expensive

I have been experimenting with various different materials over a few years, mainly on old Brit bangers, but also a few new cars as well. What I have noticed from modern production cars is that there is a great deal of bonded on material; when I have used this, it has worked with the most effect.

I have also found (for front engine cars, anyway) that the best place to apply material is the front firewall of the car, as farup under the dash as you can go, and as far down past the junction of the firewall with the floor as you can. It is best to try and use one sheet if possible. However, the greatest benefit I found in damping engine noise is doing this in combination with damping panels glued under the bonnet, in the panel areas between reinforcement bars. This has given me the best results, and I now apply it routinely to cars I buy. You need to ensure the type you use under the bonnet is flame and heat resistant; I use a foil coated rubber foam with sticky back by Terosol.

One of the few remaining Mk1 owners... #00015

I am not very used to american cars, but from what I've seen and heard, your main problem might be engine sound, not road sound, am I right?
Then your efforts should've been directed to the firewall. Apply Dynaliner, and two layers of the best dynamat there is, and dynamounts to your dashboard and you will probably hear a real difference. Also, this might be of use: get an aftermarket quiet-sounding escape system. That can work wonders on those brutish v-8s americans like so much. Good luck.
P.S. on my Golf IV, the "cover everything" approach worked fine, it's a really quiet car now (it already was, for an economic car)