Installing some new carpet: Dynamat over top OEM sound deadening?

[aread]

Hey Gents,

Got my german square-weave carpet from Auto Bahn interiors and now that I have the carpet out, I am evaluating the stock sound deadening.Its in okay condition despite a few cracks and it generally being matted down.

My question is this: Has anyone applied a layer of dynamat over top of the OEM sound deadening, and then the carpet to the dynamat? How would adhesion be with dynamat on top of the OEM stuff? Would it be better to just pull the stock SD and put down fresh Dynamat (maybe multiple layers if needed)?

I did search, just didn't see anything relating to this specific subject.

Sorry if these are stupid questions...

[gtc]

Originally Posted by aread

Would it be better to just pull the stock SD and put down fresh Dynamat (maybe multiple layers if needed)?

Yes

[ossiblue]

Originally Posted by aread

Hey Gents,

Got my german square-weave carpet from Auto Bahn interiors and now that I have the carpet out, I am evaluating the stock sound deadening.Its in okay condition despite a few cracks and it generally being matted down.

My question is this: Has anyone applied a layer of dynamat over top of the OEM sound deadening, and then the carpet to the dynamat? How would adhesion be with dynamat on top of the OEM stuff? Would it be better to just pull the stock SD and put down fresh Dynamat (maybe multiple layers if needed)?

I did search, just didn't see anything relating to this specific subject.

Sorry if these are stupid questions...

Originally Posted by gtc

Yes

I concur^^.

But first, a few cautions. The OG sound deadening material's biggest drawback is its ability to hold water which, eventually, will begin to rust the floor while being unseen. If you simply cover the old with Dynamat, if any rust has begun, you will never know until it's too late. Cleaning off the old material, inspecting the metal underneath, and addressing any rust issues found, is the first step.

As far as how much Dynamat to use, that is another topic for clarification. You do not need to cover the entire metal floor, nor do you need two layers. Dynamat is a sound dampener, which means, it is designed to reduce the vibration frequency of the sheet metal, not block sound waves. Dynamat is dense and heavy, and just like the OG material, it's function is to eliminate/dampen sound frequency of the metal, not eliminate outside noise. The little pieces inside the door skins is what gives the Porsche "ping" sound when the door is closed. The door is not totally covered. Two layers of Dynamat will add significant weight without significant sound reduction.

If you want to make the interior quieter, much better sound reduction will be gained by the carpet or even a layer of automotive carpet padding laid between the Dynamat and carpet. If you choose that route, do not glue the padding down and be ready to remove the carpet and padding should you get any water into the interior.

[aread]

Thanks guys. Didn't consider the rust issue. That might make my decision right there.

[Mick_D]

I'm planning on being certain that my windows and doors don't leak before I put an interior back in. Test for leaks before you recover the floor.

[RichardNew]

Rust may be your biggest concern. And, you won't notice this rust until it's too late.

I just used the OEM/Wurth and it works fine.



Richard Newton
Historic Racing Images

[aread]

Well crap. I pulled back the sound deadening and, sure enough, the entire bottom of the driver-side bucket is rusted through.

This is what I get for trying to tackle a "small carpet job" on my own.

Thank you LJ and Richard for pointing that out. I might have covered new carpet right over a looming rust problem that would have only gotten worse.

...I need a beer

[JabsZA]

I removed the existing material and fortunately had 0 rust.
I applied the Wurth OE sound dampener that i believe Porsche / VW use.

Really happy with the results.

[Lake Guy]

Alex, I removed my original sound deadening last year - not the funnest 911 job but not the worst either. Lots of info on how different guys did it. I primarily chipped it off with a flat blade screw driver and wooden mallet. Took some time and safety glasses are recommended. Months later I was still finding small pieces in different corners and such.

I agree with ossiblue about how much Dynamat to use. Not too much and not two layers.

Good luck.

[zippy_gg]

I used one of these from HF Oscillating Tools - Oscillating Multifunction Power Tools and removed the old sound deadening material in no time!

[john walker's workshop]

Dry ice and a rubber mallet.

[Puma]

Only using dynamat will not work. If you're after real sound deadening do a search for user Nineball and read his threads on the subject. Basically he says you need three layers. The downside is that good soundproofing is heavy, over a pound per square foot.

I've been looking into the offerings of aircraft spruce. They have a system that's a half pound per square foot. Seems like a decent compromise. I don't need a luxury quiet car but it is nice to be able to hear what a passenger is saying.

[hangar21]

Alex & all, you guys are on it! I agree with everyone, here is one other option. After removal of old carpet & padding, the clean & prep for new material is the hard part. Like most-I used Dynamat as base coat, then a friend showed me a new product called; B-quiet. Basically it's a rubber lining with a thin cushion of foam applied on top of the Dynamat. Then the carpet on top to complete the process.
My car (87) is a cab, so noise is always present, however with new interior, it's much better. Good luck with your project.
Terry

[ossiblue]

Sounds like the OP is now facing a floor repair. Welcome to the world of the slippery slope. Really not a big deal, but something you weren't expecting. Look at it as a fortunate discovery. If you want to return the car to original sound dampening, Dynamat or any other deadening material will work, and the amount need not exceed the amount of the OG material. Butyl based is better than asphalt, IMO.

If you want to increase quietness and road noise, you need to look at other materials which have air gaps, like open cell foam. That, however, introduces the possibility of water retention once again. Sound deadening and sound absorption are two different things. Porsche did not use sound absorbing materials on the floors, outside of the carpet. On the doors, the plastic water barrier and panel cards served the purpose of stifling outside noise from entering the cabin--however poorly. Covering the holes in the inside door frame with the plastic barrier cuts down on the acoustic waves entering the cabin.

[aread]

Originally Posted by ossiblue

Sounds like the OP is now facing a floor repair. Welcome to the world of the slippery slope. Really not a big deal, but something you weren't expecting. Look at it as a fortunate discovery. If you want to return the car to original sound dampening, Dynamat or any other deadening material will work, and the amount need not exceed the amount of the OG material. Butyl based is better than asphalt, IMO.

If you want to increase quietness and road noise, you need to look at other materials which have air gaps, like open cell foam. That, however, introduces the possibility of water retention once again. Sound deadening and sound absorption are two different things. Porsche did not use sound absorbing materials on the floors, outside of the carpet. On the doors, the plastic water barrier and panel cards served the purpose of stifling outside noise from entering the cabin--however poorly. Covering the holes in the inside door frame with the plastic barrier cuts down on the acoustic waves entering the cabin.

Pretty much this ^^^. Everything sound deadening is on a temporary hold until I address the rust issue. Taking the car to a body guy when I return home from San Diego to get an idea on the scope of this new project now upon us.

I did see nineballs post on the three step process, and as much as I like it, the weight is too large a sacrifice for me. Returning to at least a stock level of sound deadening is my goal here. Any less and the Mrs. won't let me take it on long trips.

I will have to look into BQuiet as well. It sound similar to the DynaPad made by dynamat that I was considering for the floor panels.

I'll post some pics of the rust when I get a chance...

[mickey356]

If the rust is in the usual place, rear passenger seat bowl, it's a fairly simple patch job....accessible from top and bottom, and depending on the size, weld a piece of metal or buy a pre-cut piece from salvage or a re-pop.

What I'm trying to wrap my head around is how to get the carpet to lay smooth with all the recommended layers of dampener and deadner. It seems like there would be a lot of cushioning and therefore difficult to get a clean look.

[Tremelune]

Interior sound deadening, noise reduction, and thermal insulation

[wayner]

Originally Posted by Tremelune

Interior sound deadening, noise reduction, and thermal insulation

Good link

And to the original poster, think of dynamat as a replacement for stock, not a supplement.

The original factory supplements in different parts of the cabin were horse hair and carpet backing ( as well as back seats...they are the biggest sound proofing component in the car)

Today there are more modern materials than horse hair

I used aircraft spruce closed cell foam over dynamat and that helped, but mass loaded vinyl ( or back seats) are a necessary next step for me to drive without ear protection

[bemmett]

Originally Posted by wayner

( as well as back seats...they are the biggest sound proofing component in the car)

^^^^ This.

I removed my rear seat backs last weekend (left in the bottoms for now) and was really surprised at how much more mechanical noise came into the cabin. Other than the volume increasing and other sounds becoming clearer, I can even hear the clutch engage now whereas I couldn't before.

[aread]

Originally Posted by bemmett

^^^^ This.

I removed my rear seat backs last weekend (left in the bottoms for now) and was really surprised at how much more mechanical noise came into the cabin. Other than the volume increasing and other sounds becoming clearer, I can even hear the clutch engage now whereas I couldn't before.

I noticed this as well. Ill be interested to see how loud it is with carpet, seats and sound deadening out, when I take it to the body shop next week.