jamiejim

PO installed subs in the open hatch spaces behind the rear wheels. They sound ok, but he just stuffed fiberglass house insulation around the sides. I have read posts about "dynomat" that can be used for this, but when I do a google search , I find both "dynomat" and "dynamat". My questions are:

Are dynomat and dynamat the same thing?
Is there a better or cheaper product to use for insulating the sub spaces?
Where is the best place to buy it - retai vs. online?
Can this same product be used in other parts of the car, i.e. firewall, inside doors, etc. to reduce the noise?

Obviously, I'm not an audiophile or I would probably no all of this, just want to get the best info from the knowledgeable rennlisters. Any info on dynomat/dynamat you can provide is appreciated. Thanks.

slevy951

Dynamat is a dampening material for sheetmetal and other resonating materials. Most stereo shops should have some form of it. The fiberglass (pink stuff?) insulation is there to help the driver breathe better. Pink stuff is not really optimum material for that. Poly fiber fill used in pillows is best. I don't know what Dynomat is....

jamiejim

slevy: So if I line the spaces where my subs are with dynamat, I should either leave the insulation (some pink, some yellow) in there or replace it with poly fiber?

Skitch

I have found in most home supply stores (Lowes, Home Depot etc...) they have some stuff called Peel n' Seal that is a roof repair item. Its a heavy tar like sheet that is adhesive backed and has foil on the outside and works great as an inexpensive Dynamat replacement. I got a roll that was enough to do two door panels, the front floor, and a rear deck for about $30.

FYI

Here is a link to an example:

http://www.randgsupply.com/Warehouse...plications.htm

goingboeing737

I lined my floorpan when replacing the carpet with stuff called FatMat. Same as dynamat only less expensive.

I lined the inside of the doors with adhesive Vascocell tape. This is the stuff you wrap around pipes to keep them from sweating or freezing. Get it at Home Depot or Lowes. It weighs next to nothing, whereas the FatMat is really heavy.

Both of these have really quieted down the interior.

FatMat website

slevy951

Take it out first and see how it sounds. You can vary the amount and density of the fill to your liking. But, since that area is not air tight, and depending on the driver being used, it may not make much difference. Experiment with it. You can't hurt anything.

Zero10

Hmm, I would say replace it with poly fiber, I have several reasons for saying that,
1) There is no fun like trying to get little glass fibers out of all of your carpet, trust me.
2) Fiberglass insulation actually poses a health risk, not a big one, but it is a proven carcinogen. However, as most people will tell you, that's only in California, and most people don't listen to it anywhere else.
3) The itch. If you ever have to work on something back there, and any of the insulation has gotten free, the itching of it will drive you mad.

Next summer I am going to use Brown Bread on the entire interior of my 944. The reasons for this are two fold, first of all I am looking to reduce the road noise, and second of all, I am building a show system in my car, and it will be taken to Db drag events and such.

Anyhoo, I was planning on pulling all the carpet out, door panels off, and the roof down, but I think I will leave the dash in there, this car has been smashed about 10 years ago, and everything is just a little crooked (the dash is tight on one side, btu has 1/4" gap on the other), so I doubt I could get it back in if I removed it.

I am a little confused about the PO's stereo, did he just put plates over the 2 storage areas behind the wheels, and use the entire area back there as a enclosure? Or did he actually put a box in there, and then stuffed around the box?
If he used the area as an enclosure, then if you remove the fiberglass, and don't replace with polyfill, you will alter the tuning and efficiency of the box, probably for the worse. If he stuffed around the box, I would replace a little of it with polyfill, to provide some damping for if the box moves, to keep rattles down or whatever, but remove most of it. If there is a box, there is very little need to put dynamat in there. Keep in mind, that small of an application will have no effect on the road noise, or on the sound from your stereo outside your car.

jamiejim

The insulation is just dumped in the bottom of the storage areas, and the main reason I want to remove it is for what you mentioned - it is a royal pain to have to pull it out if you are working in that area, and the fibers stick to the carpet like glue. PO built "plates" as you described them out of some type of 3/4" thick wood like material, but not plywood. They are painted black, screwed to the rear deck (but not through the gas tank) and look very nice. Rumor has it Santa is bringing me a digital camera, so if anyone is interested I will post some pix.

jamiejim

Does the "peel and seal" stuff have a smell too it - I have heard than some of the cheaper alternatives smell like tar? Where exactly do you put it inside the doors - on the inside of the exterior door panel or somewhere else? Is it easy to pull up the carpet to do the floor pan? If I'm not going to do the whole car (such as headliner), what are the most critical areas to start with (doors and floor?). Does the result (less exterior noise) justify the effort? Thanks.

Zero10

There are a few key areas you will want to make sure you get. To do the doors, yes, pull the panels off and do the inside of the door, making sure that first of all, it's not too thick, so it doesn't interfere with window operation, and second of all, you don't cover any screw or drain holes. Next up, you will want to cover the floor pans if you can, they let an awful low of noise through, the cover over the torque tube in specific, as well as underneath the carpet in the hatch area, it will help to isolate some transmission noise. A lot of the road noise is transferred through the suspension and control arms, so it is very difficult to eliminate. There is no real need to do the inside of the roof, it only creates a tiny bit of wind noise, my purpose is to keep as much of the sound from my system inside my car, and keep the rattles down. It would be a good idea to do the rear wheel wells as well. Those are my suggestions, that doesn't make them right =)
Alright, since he used the cubby as an enclosure, I would definately change the insulation for polyfill, and use a rug doctor or something similar to get the fiberglass out of all the carpet in the rear, it would be advisable to keep a similar volume of polyfill to keep the acoustics of the 'box' the same. There is no real need for dynamat there (unless you are doing the whole car), but it would help to keep down the noise (outside the car), and perhaps clean up the sound a small amount.

jamiejim

Do I just dump the polyfill in "loose", or put it in some kind of bag?

944JM

I mounted a 10" sub in the right rear quarter on a board cut and contoured to the area. This was covered by the black fabric used on speaker boxes. There is a small gap around the board though I was told I needed to plug it up. There is no insulation in this hole. To replace the side marker light you have to remove the speaker. On the left is another board cut to contour that holds the amp. Ditto coverage. This quarter I filled with batted wool loosely thrown in. Did wonders in knocking back the exhaust and road noise. Also you can pitch the spare tire and keep the air pump, jack and get 2 cans of fix-a-flat and a tire plug kit. Weighs less than the tire and you can 'pack' that area with insulation of your choice too. Covered the rear deck with Dynamat and wool. Make sure the hatch seal is tight. Unbelievable the amount of wind a road noise that comes in there. For me I've found that 1 sub/amp, 2 door speakers/amp, and 2 dash tweeters is more than enough. As for a show car I'm sure you'll need more! Good luck!

jamiejim

What is this "batted wool" you are referring to? Where can I get it? Is it expensive? You used the same stuff in the quarter by the amp, and also under the hatch carpet?

944JM

The wool is hard to describe. It's chopped and pressed into a mat. Not finished like cloth. This stuff is TUFF to cut too. It's about 1/4" thick. I used it as a carpet backing on the deck (over the Dynamat) and under the amp side, I wadded it up, put in a garbage bag and stuffed it into the hole under the amp (garbage bag to keep it dry if theres a leak). I don't think it's expensive. I got a sheet about 4'x8' from work as a throw away. We use this wool sheet to cut corrugated samples (boxes) on a machine to test designs and the mat gives the knife something to cut into instead of the poly table top. It's 'self-healing' in a way, which is why its tough to cut. I really don't know where to get it or how much it would cost (we get ours from the machine manufacturer). Try asking a cloth store. Make sure though that you tell them it's not 'finished' but 'batted' or 'matted'. Another idea is 'rock wool' insulation. Instead of the 'pink' stuff, this is a blown insulation that is used in attics. It takes a machine to blow it into the attic like a giant shop vac (try the local hardware store). I'd check the ingredients though to make sure there's nothing chemically nasty in it (probably not). Can't back anything with it but is great for filling holes. Just fill a garbage bag and put it in. No itchy stuff either.

Skitch

My wife's car is full of Peel n' Seal and I have never noticed any smell from it. Makes a huge difference in road noise.