Hi!

I started dynamatting the passenger door outer skin (Fabia), see picture:

before:

after:

As I learnt, dynamat is to dampen the sheet. There are also other mats for absorption.

(Sound Deadening - definitive guide to products and application - Talk Audio Forums)

Now I am thinking of two options:

1. not adding an extra absorption mat on top of dynamat. Leave as it is now (1 layer of dynamat extreme), or maybe add another layer of extreme (mainly behind the speaker hole).

2. adding an extra absorption layer on top of dynamat (covering the whole area)

Which option is best? For absorption these products are recommended:

tacmat (Tac Mat) or dynaliner (DynaLiner)

Have any of you used sound absorption mats with good results?

the 1/8" version of either of those should work just fine and will reduce high frequency noise.

Just make sure which ever one you get doesn't absorb water as they work by being open cells. If they absorb water they are suddenly closed cells so effectively just become more deadening weight.

On a quick look at that, and seeing that you have used dynamat extreme I would say just go with the 1/8" dynaliner and the do the inner door skin with dynamat, too.

HTH

Thanks for the answer. So you say both mats are effective at sound insulation.

Unfortunaletly the 1/8" version of dynaliner not available here at the moment. Tacmat (1/4") , the 1/4" and 1/2" version of dynaliner is available. 1/2" is obviously too thick. The 1/4" seems OK for me.

I made some research myself about water absorption:

Tacmat is semi-closed cell foam. After looking at it, and trying to soak water into it, it seems quite water proof.

I emailed dynamat technical support, and they said Tacmat is OK for the outer skin (behind the window). They said the absorption rate is minimal (about 1%). Looking at tacmat specs (Tac Mat), it seems true: water absorption/density = 0.11 / 7 = 1.5%

For dynaliner they state it does not absorb water (probably it's closed-cell). I googled other closed-cell foam material (http://www.noisestopsystems.co.uk/docs/spec/L_Foam.doc), they absorb at 0.3%.

SO both product should be OK. Tacmat seems to have better heat insulation, and damping (it feels as a quite dense foam). Mabye I will use Tacmat on the outer skin.

The only thing I'm uncertain about a bit is that most DIY guides use these foam mats on the inner skin, and not on the outer skin. Does this make a difference?

Basically the Dynamat type products damp by adding mass so tend to reduce low frequency noise.

The TacMat/DynaLiner type products work by reducing reflections and other factors to reduce high frequency noise.

If there is space for it over dynamat then it isn't going to do any harm on the outer door skin as long as it doesn't get in the way or soak up water as said above.

Putting it on just the inner door skin will be more effective than just the outer skin as this would stop noise entering from the surrounding areas. Doing both will be even more effective.

It's a compromise of cost and weight vs sound deadening.

Personally I'd probably just D/Mat the outer door skin, then place some D/Mat on the inside side of the inner skin and then some D/Liner (possibly with D/Mat under it) on the side of the inner skin that faces the outer skin.

I'd also place a few bits of the D/Mat and D/Liner on the door car to stop resonance. I found that D/Mat around the speaker grill area and then a few bits of foamed material elsewhere to prevent vibration and make the thing a tight fit worked really well. (Putting the dynaliner on the inside face of the inner skin would also do this, but would reduce it's effectiveness as it it compressed. It might also make putting the door car on very hard.)

Anywhere in between this will improve the car, and in some ways I'd be tempted to put the thing back together and see how it is as it is now.

You might be happy with that, at which point you have saved some serious cash

Why not use aluminium roof flashing?? Works the same and is cheaper. In one of my old cars I used this nd it was great, I got it from Wickes

The Aluminium is conductive and on a different metal could lead to an electrical effect between two metals and cause corrosion where they are in contact. (EG steel hub + alloy wheel)

For the sake of not much, I'd rather have the matting, but each to their own.

Also that would only replace the Dynamat rather than the liner

EDIT: YOu could use layers of the self adhesive roofing material for a flat roof, as that would probably have a similar effect to dynamat.

Why not use aluminium roof flashing?? Works the same and is cheaper. In one of my old cars I used this nd it was great, I got it from Wickes

I used 2 layers of flashing tape and 1 layer of bodyline car deadening. Doors are rock hard now

Why not use aluminium roof flashing?? Works the same and is cheaper. In one of my old cars I used this nd it was great, I got it from Wickes

I'm afraid that flashing tape is approved only below temperature like 70-80C. In summer and considering that the car is black, it could get hot close to where bitumen would melt, leaving a mess in the door. This is just my opinion, I have no real experience with flashing.

BTW, a very interesting article to read: Sound Deadener Showdown. I'd really like to read comments from you guys.

I used flashing tape on the floor of my old car and it was ok,i wouldnt use it on the vertical surfaces because of the adhesive is not rated above about 90'.My last car had about 5 bulk packs of stinger roadkill.So far in the ocatvia i have used 23 sheets of stinger roadkill(each sheet 18"x36") .I also have fitted some absortion matting behind the speakers.

This reminds me. Got some second skin rattle pad to fit between the door panel and the doors.

Flashing is no where near as good as the likes of Dynamt Extreme and Second skin products.

Sure it is cheap, but you need 3 layers to get the same effect.

The weight of this, and the facts that it falls off and creates a mess everywhere means I don't even think about flashing tape for doors.

On the boot floor it might be ok, but even then I'd rather use the propper items.

Have a good look around talkaudio for more advice as this has been done to death.

I found the bodyline stuff to be good and its cheap.

Putting it on just the inner door skin will be more effective than just the outer skin as this would stop noise entering from the surrounding areas. Doing both will be even more effective.

Personally I'd probably just D/Mat the outer door skin, then place some D/Mat on the inside side of the inner skin and then some D/Liner (possibly with D/Mat under it) on the side of the inner skin that faces the outer skin.

So you say it's better to put dynaliner on the inner skin rather than on the outer skin. Why is it actually? The outer skin has the advantage that it is a large continuous area, so can be covered with large pieces without seams. Inner skin carries a lot of thing which get in the way.

Finally I bought TacMat which needs an adhesive.

Which adhesive type is best for use under metal sheets in cars?

(should create a strong lasting bond, and withstand high temperature, e.g. for gluing headliner)

Your point has validity about the single solid sheet and that will make a big difference. I was comming from the single sheet large door carrier on the VAG cars which means you can get a single layer on the inner skin too.

My logic behind i is that you have the bottom and top and sides of the door to let noise in between the inner and outer skins.

In an ideal world both would work even better, but it is down to what you prefer to do and cost/time.

I'm affraid i've only every used self adhesive products, however you will want a high temp adhesive for use.

It might be worth looking at some of the impact adhesives, however I have no idea on their temperature ranges. Probably best to drop the supplier a mail and see what they say.