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Old 11-16-2018, 11:48 AM   #1
aku-aku
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Default Sound deadening?

Since I'll have to take lots of bits out of my car to do the full Dynaudio retrofit, I figure it's worth thinking about adding some sound deadening to my TDI. (Maybe it'll just focus my attention on all the other creaks introduced by the Polish roads, but whatever.)

Has anyone tried adding sound deadening, and if so, what kind did you use, in what areas, and how well did it work?

I'm currently looking at products by CTK as I can get hold of them relatively cheaply. Obviously I'm looking towards their waterproof products (the butyl insulation that's an equivalent to Dynamat, and non-porous foam), but if anyone can point me in the direction of the quick wins, that'd be a big help. I'm assuming the doors and under the rear seat are places to start - I don't know how much insulation there already is under the carpet, nor how much of a gain that would bring...?
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Old 11-16-2018, 12:16 PM   #2
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I've dabbled around with some Dynamat substitute but not needed the whole hog sound treatment. To be effective you need material that has some weight and can be bonded to metal surfaces - butyle is ideal. The biggest issues is choosing material that can get wet and can be dealt with once wet. I once used a fiber matt material on a car which all had to be removed as it had soaked up water like a sponge. The OE carpets are a good example of man made (polyprop?) material tolerant to water.

I don't know about now with fire concerns, but OEs used to use bitumen backed sheet bonded to floor pans etc. After application the external surfaces could be painted over and unless cracks developed, water would just float over the top. There are 2 aspects to sound deadening. 1st is to damp vibration in body sections which requires the material to be bonded, and second is to provide sound absorbency to 'soften' surfaces and reduce reflection. You basically want your car cabin to be sound dead with the lowest level of noise entering from outside. It is easier to manage adding some reverb afterwards if you get the cabin too dead. You can go over tapping steel body panels. If bright and live they benefit sound deadening.

I get a lot of tire noise coming into my Tdi. 235 + low profile wide tires add more so I think the footwells and footwell sides are worth looking at.. You can do some trial tests using rubber carpet underlay and carpet. I also get quite a lot of wind related noise coming through the roof which is close to your ears. If i ever pulled my roof apart I would treat the inside metal sections with Dynamat, but there's not much you can do about the glass sunroof.

There are some sound tweaks you can do on suspensions. Front and rear suspension connects the car body directly to the road through the wheels. Some car brands use rubber inserts at the top and bottom of coil springs. Under the rear seat would be easy to treat.

PS: It would be cheaper to fit 4 sockets for headphones or earbuds with an outside road mix for the driver if legal. You wouldn't need the fancy high power audio system. You could also get better sound cheaper needing less power by adding something to the sides of headrests and just add the supra base through a sub at the rear..

For before and after measurements, Bruel & Kjaer sell some very nice (expensive) acoustics measuring kit.
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Old 11-19-2018, 08:36 AM   #3
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While taking a look at how to install the amplifier mounting bracket, from poking around through the cutouts in the carpet I noticed that (at least for those with a TDI) there's a fairly thick piece of woolly underlay under the carpet already. I don't know what its sound-insulating qualities are like, but having just put winter tyres on I noticed a lot more road noise from the rear. The section under the back seat has a token piece of butyl/bitumen/whatever that was sprayed over, but there's a lot of bare metal there. The area around the rear speakers has foam insulation, as I remember, but I don't know how much effect it has.
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Old 11-19-2018, 10:01 AM   #4
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It would be logical for the Tdi to have more sound treatment. I've been running with 'All Season' tires and just put 2 new on the rear. I agree there's more road noise coming up which I would expect. Standard tires normally have a tread depth of about 8mm, whereas the tread gaps in Winter tires are 10mm. My rolling radius on the 2 new rears definitely changed after fitting them, 'cos I had to reset the TPMS. The tire shop left off and lost a VW plastic center trim. They used one guy on each rear wheel and when I checked the bolt torques, they were a lot different - shan't be using them again!

After replacing both front wings I left out their nasty water hugging foam which does give a bit more road noise, but not as much as I expected. The lump of foam doing the most for sound is the vertical profile sitting inside the wing facing the door mounts. There are a lot of air gaps which they attempt seal off with a plastic cover that has a rubbery edge seal. That's the part you see if you open a door and look in the opening next to the wing.

Sounds like the back seat is the best place to start and easy to get to. All this will change with the sunroof open or the top down!
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Old 11-23-2018, 07:24 PM   #5
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Default Focal Sound Deading

I'm late to the party here - haven't been on the site for a while.

I had Focal (pronounced "Focale") door matting put in my Eos doors and it's great! Between the sound dampening, the RCD330 head unit, the sub and amp, it's a pretty great sounding system! It's like a nightclub in my car when I want it to be...which is often!

God help my poor ears...

:-)
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Old 11-23-2018, 07:46 PM   #6
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EOS doors are well known for those long seals not keeping out water which when inside the cavity runs out the front and rear bottom door corners.If the wiper blade seals did a good job I'd say sound proofing was a good idea, but as they are I wouldn't want anything inside there holding water and accelerating window regulator rot.

Last edited by voxmagna; 11-23-2018 at 07:55 PM.
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Old 11-28-2018, 08:00 PM   #7
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Quote:
Originally Posted by D-Vancouver View Post
I had Focal (pronounced "Focale") door matting put in my Eos doors and it's great! Between the sound dampening, the RCD330 head unit, the sub and amp, it's a pretty great sounding system! It's like a nightclub in my car when I want it to be...which is often!
Is the door matting just on the visible door skin, or on the outer door skin as well? I guess bearing in mind voxmagna's comment it's safest just to put it on what's visible when the door card is removed. Did you put some foam on the door cards too?
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Old 12-01-2018, 05:06 PM   #8
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I managed to source some Vibrofiltr sound deadening mats on eBay - €40 plus shipping for a pack of 20 sheets. They claim a mechanical loss factor of 0.38, which is considerably higher than most products of the same thickness (even Standartplast's top-of-the-range only gets to 0.35), and not far off Dynamat Extreme's MLF of 0.41. Should be good stuff.
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Old 12-01-2018, 08:53 PM   #9
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No clue. Not sure I understand the questions. I had it professionally done.
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2015 Tiguan R-Line w/sport suspension. Titanium beige. 34000Km as of June 2018.
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Old 12-02-2018, 06:42 AM   #10
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Originally Posted by D-Vancouver View Post
No clue. Not sure I understand the questions. I had it professionally done.
Sorry, I'll try to rephrase.

The panel that there's stuff stuck to - did they take that out and put stuff on what's behind it? I ask because I'll have to remove that panel anyway to install the extra wires for my Dynaudio retrofit.

My guess is that they didn't and it's probably not necessary.
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Old 12-06-2018, 12:35 AM   #11
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Sorry, I don't know. Sounds great, though!
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2015 Tiguan R-Line w/sport suspension. Titanium beige. 34000Km as of June 2018.
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Old 12-06-2018, 05:28 AM   #12
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No problem, thanks anyway. I'll see how far my box of Vibrofiltr gets me, and if I can avoid disassembling the door I will.

Probably they avoided it too - doors on other cars seem to only be solid on the outside, not on the inside as the Eos doors are; no point opening the door panel up if there's no need. The insulation you can see will block road noise well, the only thing you'd potentially not get is vibration damping of the outer panel, but I reckon VW stuck a token piece of butyl on them so it wouldn't be a big deal. I'm aiming to do some work on this at the weekend, so we'll see.
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Old 12-09-2018, 08:10 AM   #13
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Quote:
Originally Posted by voxmagna View Post
Sounds like the back seat is the best place to start and easy to get to.
From the voxmagna-is-right-again department: the metal under the back seat is single-layer sheet metal with nothing between it and the road. There's even a small hole in it that you can see the road through. VW put some token bitumen in the middle of it, but the sides both make a rather nasty clang when flicked with a fingernail. The rear side panels seem pretty poor, too - although they're double-skinned and there's some bitumen deadening on the base, the sides (inner and outer) are likely culprits too. There's nothing doing about the outer parts, as the clearance for the roof rails wouldn't permit, but at least the sheets that the speakers are mounted on could get some attention. The rear arches are lurking under the foam beneath the speakers as well - and that foam is open-cell, so it likely won't do much good in terms of sound insulation. Anyway, I noticed that much of the noise comes from behind me when I'm driving, and that conclusion does match up with my observations.

Of course, now it's a bit cold out, so this will have to wait - at least until I can get a fan heater to the garage! The temperature needs to be at least 15C for butyl sheets to stick properly, and it's advised to use a heat gun for better adhesion too. (A hairdryer would likely achieve the same effect, but with lower risk of burning stuff for clumsy types.)
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Old 01-07-2019, 12:38 PM   #14
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A trial of insulating under the rear seat with a piece of 10mm foam carpet underlay ("pianomat") seems to have made a dramatic difference to the noise level, especially on snowy roads. That'll stay there until the weather warms up and I can do a more proper job!
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Old 01-10-2019, 09:33 AM   #15
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There isn't much treatment on that section and I can see it making a difference. I've used rubber carpet underlay before, just watch out for any build up of condensation between the underlay and the steel. I think that's why they bond sound deadening panels and paint over so there's no air gap.
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