Jlaa

Hi folks,

I was wondering if anyone had any opinions on the necessity of putting dynamat on the rear firewall?

Background -

I have a 96 C2 with fister stage II exhaust and a motorsound airbox. The sound of the car is lovely. I use the car as a pleasure car. I do not commute with the car.

My gripe with the car is that the stock non HiFi stereo has atrocious sound quality. 20% of the time when driving the car, i wish to listen to music.

I spoke at length of Rod Birch about upgrading some componenents and one of the last things he suggested was to put dynamat on the rear firewall to "cut down on heat and noise". Weight concerns aside, does anyone have any thoughts on this?

My first inclination would be NOT to do this as I love the sound of the car too much. I have read in threads that this helps cut down road noise in 964s as the rear suspension is less isolated from the body. Wondering if anyone has any thought on whether this is needed for a 993. Final note - I am not an audiophile ... I will not be using subwoofers. If i could get my 993's stereo to sound like the stock stereo on my 2006 Volvo I wold be thrilled.

Thanks

sacman

I had this done by Rod himself and it does help with the noise significantly. I wish I can do more. It's easier to hear the engine sound by opening the windows.

NP993

I did this on my 993 coupe after removing the sound pad that is in the engine bay. I completely covered the inside of the rear firewall with Dynamat, from the top of the rear seat buckets up and back to the bottom of the rear glass. I actually took decibel readings before and after (there's an app for your phone). It made virtually no difference -- a one-decibel difference to be exact. What I found really makes a big difference in the sound level, and especially the detail of the sound, is the thick mat under the rear deck (the big shelf the speakers mount to). I think for Dynamat to make a sound (as opposed to vibration) difference, one would have to cover a lot more of the rear of the car with it than just that one area.

Jlaa

Thanks sacman ... Yes I would be doing the same as well ... Having rod do the dynamat install potentially. Now that the dynamat is installed and has quieted down the engine, Do you mean to say now it is easier to hear the EXHAUST sound WHEN window is open?

Or do you mean to say that since the dynamat has quieted the engine noise down that you now OPEN THE WINDOW to hear the engine noise?

Jlaa

Hi NP993 ... Actually you bring up a great alternative ... Thanks. Since my engine compartment sound pad is drooping already, I could always install the dynamat .... And if the result is too quiet, I could forever eliminate the engine compartment sound pad ...

1990-964

I went through several types of soundproofing with my previous 964 to try and quiet it down, all to little or no avail. I tried an elastomer brush on liquid called Quiet Car and it did not help. Also tried Cascade Audio Engineering sound pad over the whole rear interior area and lastly had a custom heat barrier material and Dynamat installed. None of it ever made a noticeable difference. My 993 is so much quieter than the 964 that I have never thought about trying to make it quieter, and I always listen to the stereo. I personally would not ever bother again. Tires make more of a difference in sound generated, but with the superior isolation of the 993 rear suspension I don't find it necessary.

FlatSix911

I installed Dynamat behind the rear seats and found very little improvement in Hi Fi sound quality ... I now listen to the motor rev

csmab

I installed dynamat in the lower portion of the doors and rear firewall and reduced the noise by 2-3 decibels. Road noise has definately been reduced. Hifi system sounds the same. It was a worth while project.

Ed Hughes

You say "weight concerns aside", but that is exactly what I would consider. It's my belief that this stuff is pretty heavy.

Jlaa

Hmmmm .... I'm just talking about the rear firewall ... Maybe no more than 15 pounds.

For those that have indicated that the dynamat mat a good difference, is it-

1). Reduction in general noise cruising at 70mph in 5th or 6th gear?

Or is it

2). Reduction in engine noise running through 1st, 2nd, and 3rd gears from 2000-5000+ rpm?

I'm thinking reduction in #1 is desirable but reduction in #2 is not.

Ed Hughes

Well, 15lbs isn't a lot, I suppose. But, based on the comments about any difference being negligible, seems like diminishing returns.

sacman

Sorry for little details on my initial reply. My experience with engine noise might a little misleading because there were a lot changes. My car came with the non-hifi with crappy speakers front and back so all the sound that I heard before the change was from the engine and distorted sound from the speakers. I had Rod put in a brandnew system with 1 of his own sub (highly recommended), alpine amp, Kenwood deck, focal component set in the front, new wiring, dynamat done in the rear. The sound difference was night and day.

NP993

Rear firewall takes a few pounds of dynamat to cover -- not even close to 15.

potent951turbo

No offense meant, but why would you buy this type of car if you want to silence all the amazing sounds that make it so unique?

Quadcammer

did you even read the thread?