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Old 01-08-2012, 10:08 PM   #1
f1vlad
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Default Ideas to reduce cabin cat-back drone? Sound deadening with Dynamat?

This weekend I had SPT cat back installed on my '08 WRX. It's a third Subaru, where I installed this cat back. Previous were GD chasis.



I have to tell you on GR internal drone is a bit too much. So I've started exploring on what to do next to diminish that annoying drone which gives almost a headache.

I came across one probably worthy route -- use sound deadening with Dynamat. Anyone knows or has experience with it? Will it be effective at all?
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Old 01-08-2012, 10:24 PM   #2
slimfit
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Should help a little. My buddy has an '11 hatchback and it is way louder than my sedan, it's just the nature of the beast. Not to go off topic, but why are there so many stickers on that thing? Was it shipped without a box!?!?
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Old 01-08-2012, 10:26 PM   #3
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i know for the gd chassis if you cover the part under the seats with dynamat it reduces the in cabin drone of an aftermarket exhaust substantially, for those with low volume exhausts such as the spt ones it basically eliminates the drone all together

i'd say that's a good spot to start, i would first use dynamat in the trunk space just under all the carpeting, not on the sides or roof or the hatch itself, if that's not enough work your way foward and sound deaden the section under the rear seats, that there should be enough to decrease the drone for you
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Old 01-08-2012, 10:49 PM   #4
f1vlad
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Quote:
Originally Posted by slimfit View Post
Should help a little. My buddy has an '11 hatchback and it is way louder than my sedan, it's just the nature of the beast. Not to go off topic, but why are there so many stickers on that thing? Was it shipped without a box!?!?
Yeap it was shipped without box just like that. I bought it used.

Quote:
Originally Posted by brew02wrx View Post
i know for the gd chassis if you cover the part under the seats with dynamat it reduces the in cabin drone of an aftermarket exhaust substantially, for those with low volume exhausts such as the spt ones it basically eliminates the drone all together

i'd say that's a good spot to start, i would first use dynamat in the trunk space just under all the carpeting, not on the sides or roof or the hatch itself, if that's not enough work your way foward and sound deaden the section under the rear seats, that there should be enough to decrease the drone for you
Thanks, that was exactly my plan.
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Old 01-09-2012, 09:13 AM   #5
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You need sound isolation, not deadening. Dynamat will not solve this. Dynamat stops vibrations in metal panels, effectively making cars stop sounding like tin cans when a subwoofer or whatnot is working. You'll need a closed cell foam layer to be the barrier for noise coming through panels. (Ensolite is an option, but not the only one).

www.sounddeadenershowdown.com/
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Old 01-09-2012, 09:29 AM   #6
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Dynamat will help with drone tremendously. It will not help to lower the noise, though.

For my STI hatch, I put vibration dampener (Dynamat and Raammat) under the spare tire, on the rear hatch (under the plastic), and directly behind the rear seats there are 3 black metal pieces that like to create a racket that I put some Dynamat on also.

Like the others have already stated, if that's not enough, work your way forward and then up/down. IMHO, dampening the roof didn't do much to reduce drone. It helped to make the car sound like a car instead of an empty soda can when it's raining, though.
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Old 01-09-2012, 09:58 AM   #7
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infinite012, if you have pics could you post pics of what you did behind rear seats on metal pieces? Thanks.
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Old 01-09-2012, 10:01 AM   #8
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Now that I don't follow. Drone is not a vibration from panels, it's noise from the exhaust. Butyl mats, such as Dynamat or Raammat, don't stop noise penetration.
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Old 01-09-2012, 10:58 AM   #9
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I'm looking to solve this same issue. I like hearing it but hate seeing my wife suffer the drone and hold herself back from complaining...
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Old 01-09-2012, 10:59 AM   #10
infinite012
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They don't stop the noise penetration, but it helps to reduce the frequency at which the metal vibrates/resonates. Drone is (in my definition, which may be incorrect) primarily caused by resonation of the engine/exhaust with the sheet metal.

Quote:
Originally Posted by f1vlad View Post
infinite012, if you have pics could you post pics of what you did behind rear seats on metal pieces? Thanks.
Sorry, I don't have pictures. Just take a look at the black metal pieces under the carpet nearest to the rear seats. If you hit the pieces with your fingertip or a screwdriver, they will "ping." You can either put dynamat on top or beneath (I chose to remove and put Dynamat beneath the pieces), so next time you hit it with a screwdriver, it will "thud."

I just followed advice on here to start tapping on metal - if it pings, put some Dynamat on it.
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Old 01-09-2012, 07:35 PM   #11
f1vlad
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Sounds good. It's been freezing lately, I sure will start poking at it as soon as it warms up.
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Old 01-11-2012, 02:36 AM   #12
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i recently soundproofed my whole wrx. it took about a week where i had all the panels out and all the seats etc, so i experimented quite a bit with stuff

IMO dynamat (or other foil + butyl products) help a lot for making the car seem more solid - the speakers sound far better, the doors close with a thunk, and it's rattle free (other than the rearview mirror )

what was the most effective for me, after a single layer of dynamat all over the trunk, was a piece of dynapad - much heavier foam + vinyl + foam layer

i made a single cutout to fit the trunk floor, and then 2 smaller pieces which i sort of tucked into the void between the trunk floor, trunk liner and those flappy air vent things (see video)

it's made a HUGE difference and i haven't sealed up the vents, just placed the mat over the top, so they still operate, but you can't hear anything from them now and the drone is basically eliminated. it's especially noticeable on a cold startup.

i have an SPT exhaust + cobb DP, so it's noisier than stock for sure.

here's where your drone is entering the cabin:

Last edited by robwormald; 01-11-2012 at 02:41 AM.
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Old 01-11-2012, 02:36 AM   #13
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double post
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Old 01-11-2012, 09:48 AM   #14
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i've been contemplating on whether or not to dynamat/raamat. i have $60 ebay bucks so figured it was a good time to get this

my gf always complains its too loud. i love it

but doing the trunk, spare tire area and beneath the rear seats would be enough to lower the drone? how much material would i need? would 25 sq ft be enough or would 50 sq ft be more than enough?
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Old 01-11-2012, 10:45 AM   #15
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Keep in mind, you need not coat surfaces in dynamat for effectiveness, just in the center of a panel that resonates. The objective is to add weight to panels, not add a second layer. I got a 100sqft roll of raammat, or however its spelled, and was able to do the entire trunk area, all four doors, the floor, and under the rear seats with maybe 35 sqft leftover.
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Old 01-11-2012, 03:57 PM   #16
Ernest
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Do a search on sound deadening or drone. I remember a thread where a guy had pictures of the entire rear of the wagon that had dynamat and ensolite. I did the same thing and it worked well. Turns out in the 04 noise can come right into the car from the spare and the jack area. I also put ensolite on the rear strut tops and wheel well. It dulled it just enough to not annoy me. I have Prodrive oval exhaust - stage 2 with 3rd highflow cat.
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Old 01-12-2012, 02:27 AM   #17
f1vlad
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Quote:
Originally Posted by robwormald View Post
i recently soundproofed my whole wrx. it took about a week where i had all the panels out and all the seats etc, so i experimented quite a bit with stuff
...
Thanks, definitely showcases the drone!
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Old 03-05-2012, 11:17 AM   #18
f1vlad
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So I finished my little project of sound deadening. The result is acceptable but not great. The drone and mostly bass diminished enough to not drive me insane, but I think I'll still be looking at quieter exhaust after all.

Here's a picture of first layer of brown bread:



And then a layer of ensolite:

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Old 03-07-2012, 08:34 PM   #19
dewmanco
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I am thinking about doing this with my '10 STi. Any advice for installing the dynamat or said sound deadening material? I heard it's a pain and the stuff is super sticky.
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Old 03-08-2012, 10:08 AM   #20
f1vlad
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It isn't really that sticky, at least material I used, so this isn't anything to be worried about I think. The biggest pain is taking everything apart.
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Old 03-08-2012, 12:27 PM   #21
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A big difference will be getting dampener inside the rear wheel well arches from inside the hatch.
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Old 03-08-2012, 03:25 PM   #22
Jayp5150
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May I ask this; will the SPT exhaust burn in some, then?

I have a little over 800 miles on mine, and it's very quiet (at least from what I'm used to).

I can literally barely hear it at 75 with the windows up.

Maybe I'm just deaf... or just used to a much more aggressive exhaust note.
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Old 03-08-2012, 05:08 PM   #23
f1vlad
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Quote:
Originally Posted by Jayp5150 View Post
May I ask this; will the SPT exhaust burn in some, then?

I have a little over 800 miles on mine, and it's very quiet (at least from what I'm used to).

I can literally barely hear it at 75 with the windows up.

Maybe I'm just deaf... or just used to a much more aggressive exhaust note.

I have put about 2000 mi and no different in my case, not louder or quieter.

I have suspicion that maybe my exhaust is rubbing somewhere.

But wait, you have hatch? Did you have OEM exhaust before? And not SPT? I did and in my case noise difference is very significant. At all speeds. I can surely hear it at 70.

Wait you have WRX? Isn't STi louder overall inside than WRX?

Here is excerpt from Owner Reference Guide SUBARU IMPREZA WRX STi.
Quote:
"Because your WRX STi is a performance machine above all else, the driving performance of your WRX STi has been prioritized above driving comfort, which can sometimes result in higher NVH level (noise, vibration and harshness) under certain circumstances"
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Old 03-08-2012, 05:27 PM   #24
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Quote:
Originally Posted by f1vlad

I have put about 2000 mi and no different in my case, not louder or quieter.

I have suspicion that maybe my exhaust is rubbing somewhere.

But wait, you have hatch? Did you have OEM exhaust before? And not SPT? I did and in my case noise difference is very significant. At all speeds. I can surely hear it at 70.

Wait you have WRX? Isn't STi louder overall inside than WRX?

Here is excerpt from Owner Reference Guide SUBARU IMPREZA WRX STi.
Yes, WRX hatch. My bad, I wasn't aware there was a difference as far as deadening was concerned.

To your other question, I ordered the car with the SPT, so no comparison. I paid attention on the way home today, and my tires are as loud as the exhaust lol. I mean, it's audible, but not intrusive.

Didn't mean to throw you off... that's what I get for being online at work
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Old 03-08-2012, 06:39 PM   #25
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+1 for closed cell foam and mass loaded vinyl

here is a product that has been debated/tried throughout DIYMA and is said to be quite effective at ~1lb/ft^2

http://www.homedepot.com/webapp/wcs/...ocStoreNum=159
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