How To: Properly/Inexpensively sound deaden a car, long and useful Options

[MoralWarfare]

Please Note: This How-To will omit warranties on new cars, as it is considered a fire hazard and major body modification.

For the limited amount of time I have been in the audio "scene," I have noticed the lack of alternative choices for sound deadening. Of course, most people will tell you that dynamat is the best stuff you can buy, and RF Noisekill also helps. True, these products work (dynamat working predominently on large flat surfaces), but they are very expensive in comparison to my proceeding option.

I have been working on a school project (building an SQ car with a mentor) for a few months, and one trick I've learned from my mentor (a certified USAC judge, 4th in the country for SQ in 1998, top competitor in RI for the same year, etc.) is that you don't have to pay hundreds of dollars on sound deadening material.

See, the main focus of sound deadening is not for higher SPL. In fact, it can take away from SPL scores because sound deadening eliminates body rattle, which adds to your score. The focus is to create mass and rigity, therefore heightening your car's ability to resonate and isolate frequencies, lessen body chatter, and heighten SQ. Therefore, you need not expensive sheets of dynamat and big cans of RF Noisekill that got for 20 bucks a pop.

The answer: Go to your local Benny's, and pick up some three part expanding foam, and Duplicolor sandable, paintable, rubberized undercoating. They go for about 5 dollars a can, and you will need anywhere from 8-20 cans each to sound deaden your whole car (6-10 each for the trunk, depending on size).

Now, I will explain how to sound deaden your trunk (the rest of the car follows the same procedures). Take out everything. Your spare, the carpeting, etc. You want the trunk down to bare metal. Puncture your firstcan of expanding foam, and make sure to be wearing gloves, as this stuff gets very messy and sticky. You want to spray the foam in every crevace you can afford to spray into. The screw holes, wheel wells (if possible), absolutely everywhere that looks like it could be detrimental to sound quality. Don't forget your trunk door as well, which creates a LOT of rattling in most cars with high powered audio systems.

After the expanding foam is sprayed, you need to wait AT LEAST 24 hours for it to fully expand and dry. When it has dried, smooth all bumps and lumps with a razor knife, and poke holes where there used to be holes (where your panel buttons went, for example). Next comes the paint!

You want to lay this undercoating on THICK. Especially in large, flat places, as these spots experience the most body flex. A triple coat is generally reccommended, but larger amounts are fine. This coating will require a full day to dry as well. After that day is up, you can lay your carpeting back down if you wish, or paint over the flat black with something more appealing.

There you have it. Your car should sound whisper-quiet when your system is turned off and you're cruising, and your sound quality scores should be much better if executed properly. These procedures will yield hundreds of dollars of saving for sound deadening, and even better results than products such as Rockford Fosgate Noisekill and Dynamat. By the way, reccommended areas to heavily focus on are as follows:
Trunk
Doors (will require panel removal)
Firewall
Floor

If there are any questions, feel free to email me or post on this thread. Pictures up on page 5 of my cardomain site:
http://www.cardomain.com/memberpage/473329

-Joe.

[celicarocker]

yo man where you from in RI? im there just about every day for school/work....

[DmVinny]

$5 a can times 20 = $100 times 2 = $200

$200 for the stuff, and about 10x the labor vs. deadening materials...

i dont see the efficiency in that... mho tho...

[3TST]

I went into my local hardware store, picked up a 1.5mx0.05mx20m roll of insulation carpet
(smooth one side and foam on the other), which is used in the construction industry.
I guess it is similar to carpet underlay but thicker.
Anyway, it cost me the equivalent of about $20 and I used that for the whole car, panels, boot, etc..
Yes, it's a pain in the a*s to cut to shape, fit and fix but it's a cheap solution that actually works.

This post has been edited by 3TST: Mar 23, 2004 - 7:25 AM

[MoralWarfare]

that carpeting sounds like a good solution dude.

I did my whole trunk/rear of my car for 110 dollars. The thing is with this stuff is that you want to use it selectively. Don't overfill anywhere, as it can create body flex. Don't use in high end cars (well, the undercoating is ok) as it can get costly to work around if a panel needs replacing.

Though you disagree Vinny, the ability to sound deaden your WHOLE CAR for 200 dollars is phenomenal. get a price quote from any place that uses dynamat, it will be double this, triple, even quadruple... Not to mention this saves so much weight. Total weight i added: 1 lb. If using dynamat which only works well with big flat panels and the such, it would have been a LOT more.

I don't expect you to believe me, it's easier to follow mass opinion.

[Crzybakerdog]

good stuff but would it be possible to see some pictures of the spraying on and what not. also if you go over the holes wouldnt it be difficult to get screws and other things back in them as you did fill them up with expandable foam. just a thought i had; if you stuck in temorary nails or something small for each screw hole inside the trunk. would that be an option? or is the point to cover anything and everything? i could be wrong but i thought i would ask if i try this, this summer

[MoralWarfare]

you poke the holes out after the foam has expanded through them. Then you can put your panel holders back in with ease. pics are up on page 5 of my cardomain site (in sig and also at the bottom of my write-up).

[brianforster]

where else did you do this?

im having a hard time grasping on what other areas you would sound deaden, or what areas will allow you to just spray and let dry

do you do it to the doors and back seat panels where the speakers go?

[DmVinny]

[MoralWarfare]

good idea with the plywood. Oh man this **** is messy, I'm not trying to deny that or anything. It's just for the purpose of my car I need to take the extra time to do the shaving and foam and such. This is just one viable technique.

[CelicaDEATHdie]

http://www.secondskin.net

This post has been edited by CelicaDEATHdie: Apr 1, 2004 - 3:19 PM