924Board.org

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

You know, for when that body under the hatch cover starts getting angry and you don't want the cops to hear?

"While I'm in there" replacing all my carpets, I want to look into soundproofing. The stock 931 interior uses 1/2" thick heavy rubber-backed insulation under the carpets in the floor and hatch. There must be a better alternative...

Does anyone have experience using dynamat? Seems like I could replace the removeable factory soundproofing (which is probably mold-infested anyway) with this stuff. Not to mention, add some to the doors and under the vertical carpet surfaces too. Is this stuff heavy as lead? Will it soak up water/moisture if I leave the window open? Will I be able to blow the windows out of the car with the stereo?? Sweet...

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1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

Nick, when I replaced my carpet, I just pulled out those big thick rubber mats in both the passenger compartment and the trunk. Didn't replace them with any sound absorbing material, just put the aftermarket carpet in which had "some" sound proofing in the same areas. I haven't noticed it being any louder.
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1987 951 - M193 Version for Japan

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

I'm not sure how much good those heavy mats do to begin with.

I did come across this-
http://www.sounddeadenershowdown.com/

It's apparently a little out-dated. The edead company has a ^2 (squared) version which is butyl based and still amazingly cheap at ~$100 for 100 sq ft. I think this is what I'm going with. There is a good bit of cabin noise as is and I think I can quiet this down tremendously. Not to mention trade out the old heavy and moldy mats for something a tad lighter and much better performing.

I'm surprised nobody here has messed around with this?
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1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

Nick the Dog,

Here's a thread from Pelican on a guy that went pretty far to deaden sound in his 911 using aftermarket means, I thought it was very informative.

You'll have to excuse the fact that it is a 911 and not a 924, there is no accounting for taste!

http://forums.pelicanparts.com/showthread.php?s=33ba1d5371a516d8a8475763a2274f4d&threadid=331520&highlight=interior+project
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1987 951 - M193 Version for Japan

czechsmola · Posted: Sat Apr 14, 2007 8:19 am Post subject: Dynomat

there is a cheaper substitute, cant however remember what its called. One of my friends who is quite into Car audio has a Powerful set up and he recently installed the stuff through out his whole car and it made quite a difference the speakers now sound much better, giving them a cleaner sound, and the sound from the car is trapped in more. you can be blasting the stereo and it would not travel out side of the car as much as a before... as of absorbing water its pretty much Rubber tape so no it would not absorber water. However it is heavy. but if you are concerned about the acoustics of your car then do it.

462avi · Posted: Sat Apr 14, 2007 3:00 pm Post subject:

nick

I have used dynamat and so have my friends. It is great stuff for deadening sound but I would be hesitant to put it in my Porsche. One simple reason, it is heavy shit and adds a lot of weight. Just my two cents. Maybe some light weight honey comb or egg carton style foam would be better. The idea is not so much thickness but density and air does not conduct sound well. Maybe closed cell ethifoam.

Geoff
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2005 C230K
2002 grand cherokee with 4.7L

czechsmola · Posted: Sat Apr 21, 2007 4:50 am Post subject: soundproofing

I found out what my friend put onto his car... Its called B-quite,,,, for 100squre foot its 100$ and the shipping weight was about 15lb so you could roughly figure that if you added the whole 100 feet then you would only gain about 12 lb or so.... which is not to bad

NEMESIS · Posted: Sun Apr 22, 2007 10:55 pm Post subject:

I've replaced the insulation under the carpets with foil faced bubble wrap insulation. Cheap, light, and available at your local home improvement center. Glue it in with the same spray adhesive used on the carpet.

In areas like the rear hatch, passenger kick panels, and the spots at the base of the rear seat I used jute felt from the upholstery shop in town, $4 per ft. on a 48" wide roll and glued them in place (not in the hatch).

I'm not sure on the exact noise level but my cars appear no louder than they were with the OEM stuff in there, they just smell a little better

and I did two cars for around $120 with plenty of jute felt left over.

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Going with the butyl-based eDead. Price is definitely right and it has similar specs to the more expensive bits. I'm going to start with the interior firewall and floors, although I imagine the doors will make the most dramatic change.
_________________
1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet