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05-25-2012, 10:09 PM | #1 |
Scooby Specialist
Member#: 139465
Join Date: Feb 2007
Location: Lafayette, Louisiana
Vehicle:2011 STi Limited Satin White Pearl |
how to quiet interior of car from SPT exhaust
I have a 2011 sti. I also have the SPT exhaust for it. I love the sound from the outside, but on the inside there is entirely too much bass from the exhaust at just about all rpm. I bought this exhaust because it was said to be the quietest, but if this is quiet then I believe this dual exhaust is just prone to being too loud - in my opinion.
Anyway, I want to quiet the bass that comes into the car without modifying the actual exhaust. Like an audio mat or some sort of insulation board. I once owned a GTi with a Magnaflow exhaust and it had a drone at 3000 rpm. I went to a construction site and asked the guys who were installing wall insulation board in the mechanical rooms (good for low frequency sound absorbtion) asked for some drop offs. I took it and cut it to fit the trunk of the car, fit it in and then put the trunk floor board with the carpet back on top of it. The trunk was flat so it was easy, but the board was 1 1/2" thick, but in the end it looked OEM and the drone was all but gone. It was really light too. The sti sedan trunk ramps up toward the back seats and that might make it a bit more difficult. Is there any other product out there anyone knows of? Do they make some sort of sound absorbtion mat that can wrap the exhaust itself to quiet the bass at its sorce? I really would rather not put the adhesive mat in my trunk to avoid adding the weight.
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05-25-2012, 10:17 PM | #2 |
Scooby Newbie
Member#: 267996
Join Date: Dec 2010
Chapter/Region:
E. Canada
Location: Near Montréal, Québec
Vehicle:2011 Wrx Rallye blue |
I only have experience with dynamat. I don't know what you do with your car, but the added weight is minimal. It's about 1 pounds a sheet. You need about 4 sheets.
It's flexible, thin and easy to install. For the sound, i'm using for my 11 wrx a lachute performance downpipe, ajd the drone isn't that bad. There is probably better option but for me it's enought |
05-25-2012, 10:41 PM | #3 |
Scooby Specialist
Member#: 33850
Join Date: Mar 2003
Chapter/Region:
NESIC
Location: Pittsfield, MA
Vehicle:2006 WRX Wagon WRC Blue |
bought exhaust for sound.
sound too loud. remove exhaust, replace w/ stock? or if it's too loud, you're too old. |
05-25-2012, 10:52 PM | #4 |
Scooby Newbie
Member#: 298237
Join Date: Oct 2011
Chapter/Region:
Tri-State
Vehicle:2011 STi 4dr Stg 1+ DGM |
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05-26-2012, 12:29 AM | #5 |
Scooby Newbie
Member#: 318280
Join Date: Apr 2012
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I will buy your SPT.
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05-26-2012, 12:30 AM | #6 |
Scooby Newbie
Member#: 321303
Join Date: May 2012
Chapter/Region:
MWSOC
Location: Indianapolis, IN
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05-26-2012, 12:44 AM | #7 |
Scooby Specialist
Member#: 33850
Join Date: Mar 2003
Chapter/Region:
NESIC
Location: Pittsfield, MA
Vehicle:2006 WRX Wagon WRC Blue |
I seem to recall someone saying dynamat wasn't good for the frequencies associated with car exhaust but better for the frequency of road noise.
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05-26-2012, 01:01 AM | #8 |
Scooby Newbie
Member#: 321303
Join Date: May 2012
Chapter/Region:
MWSOC
Location: Indianapolis, IN
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I had a Foxbody that was dumped right before the rear axle (with gigantic heads/cam) and dynamat helped me out a ton.
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05-26-2012, 04:46 AM | #9 |
Scooby Guru
Member#: 60082
Join Date: Apr 2004
Chapter/Region:
MWSOC
Location: Minnesota
Vehicle:2004 Forester STI Silver |
The drone sound is typically sheet metal vibration. If mechanically excited, the chassis will vibrate and become its own speaker. It will create sound. The exhaust makes sound. That sound hits the sheet metal and excites it. The sheet metal vibrates. Vibrating things make noise. Stop the vibration, stop the noise. Sheet metal is good at blocking sound. If it doesn't vibrate, it will reflect most of the sound.
Products like Dynamat are designed to stop vibration. Cascade Audio Engineering and Second Skin Audio offer some of the best sound deadening products available and at nicer prices than Dynamat. The butyl/aluminum mat should be used sparingly, only about 25% coverage and only on large, flat surfaces. Corners and curved surfaces are much more rigid and much more resistant to vibration, so mat isn't needed in these locations. You're just trying to stop the ringing. Butyl/aluminum mat is a terrible, terrible blocker of sound. However, lead or vinyl are great blockers of sound. Sound blocking is about coverage, so this is the material you actually want to use to cover everything. It's doing the same work as your sheet metal, windows, etc. just a blocking tool. It's most often foam backed to decouple the material from the vibrating surfaces as to help prevent transmission of sound through excitation. If you have audible sound coming in that isn't sheet metal excitation, this is what you use to block the sound. I will note that these deadener products are highly beneficial for other modifications like bushing upgrades that can transmit more vibration to the chassis. For example, engine and transmission bushing upgrades can create a moderate mid rpm drone very similar to that of a loud exhaust due to creating a similar level of panel vibration. These items, when used properly, help quiet the car back down to very tame levels. These also tend to be good thermal barriers too, so you also get improved efficiency of the HVAC system too. |
05-26-2012, 10:26 PM | #10 |
Scooby Specialist
Member#: 100524
Join Date: Nov 2005
Chapter/Region:
RMIC
Location: Denver
Vehicle:2012 WRX SWP |
I was thinking about getting all weather floor mats and trunk liner. This might help a bit.
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05-26-2012, 10:33 PM | #11 |
Scooby Specialist
Member#: 277630
Join Date: Mar 2011
Chapter/Region:
MAIC
Location: Rockville MD
Vehicle:2007 WRX TR WRB |
i have a foxbody mustang too with the same dumped exhaust setup but with flowmasters and motor work/blower and the bass will give anyone a headache. its not a daily driver at all. but if your exhaust is too loud id just sell it and but the stocker back on. stis sound good to me stock
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05-27-2012, 02:40 AM | #12 |
Scooby Guru
Member#: 268310
Join Date: Dec 2010
Chapter/Region:
SCIC
Location: So Kali
Vehicle:2011 SSM STI saloon Church! |
I have the Invidia Q300 on my sedan, OP, and I'm very happy with it. I bought it because I heard about drone with the SPT. The Q300 has no drone to speak of, during highway driving or otherwise. Deeper in tone, but still very smooth and quiet in the cabin. I know you're diggin' the signature "boxer" sound and don't want to give it up completely by going back to stock. Sell your SPT and look into the Q300.
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05-27-2012, 02:52 AM | #13 | |
Scooby Newbie
Member#: 268286
Join Date: Dec 2010
Chapter/Region:
W. Canada
Location: Alberta
Vehicle:2011 STi Dark Grey |
Quote:
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05-27-2012, 03:04 AM | #14 |
Scooby Guru
Member#: 268310
Join Date: Dec 2010
Chapter/Region:
SCIC
Location: So Kali
Vehicle:2011 SSM STI saloon Church! |
On a sedan? I know the Q300 is pretty loud on a hatch, but I've never heard anyone complain about it on the sedan. I do only have the catback installed...so far.
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05-27-2012, 11:14 AM | #15 | |
Scooby Newbie
Member#: 203159
Join Date: Feb 2009
Chapter/Region:
AKIC
Location: Calgary, Alberta
Vehicle:2008 WRX - Stage 2 WRB |
Quote:
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03-13-2013, 02:42 AM | #16 |
Scooby Specialist
Member#: 284420
Join Date: Jun 2011
Chapter/Region:
SWIC
Location: Lakewood, Ca
Vehicle:2011 WRX Sedan SWP |
I have a sedan and catted Invidia and it sounds great to me. No drone imo. The dp does make a difference though wether it be stock, catted or catless as far as sound.
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03-13-2013, 05:58 AM | #17 |
Scooby Newbie
Member#: 319696
Join Date: May 2012
Chapter/Region:
BAIC
Location: Bay Area
Vehicle:2012 Subaru WRX STI DGM |
sell the SPT, get different exhaust. I have a maddad whisper. opens up when on it. louder than stock. no drone. i wish it a tad louder though
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03-13-2013, 08:51 AM | #18 |
Scooby Specialist
Member#: 187013
Join Date: Aug 2008
Chapter/Region:
MWSOC
Location: Buffalo Grove, IL
Vehicle:2013 ST |
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03-13-2013, 09:42 AM | #19 |
Scooby Specialist
Member#: 284420
Join Date: Jun 2011
Chapter/Region:
SWIC
Location: Lakewood, Ca
Vehicle:2011 WRX Sedan SWP |
Lol, I never look at dates.
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