# Second Skin dampening products review



## npdang (Jul 29, 2005)

I'd like to thank Ant from www.SecondSkinAudio.com for donating the products used in this review.

I received 2 damplifier pro door kits, a pair of speaker pads, a rattle mat, overkill pro, and a bottle of spray adhesive. What's also nice is that all the little tools were included as well, including a door clip removal tool, a razor with extra blades, and a roller. Excellent!

First, the stock dampening. Not bad, you can see there's a rubber padding added on top of the plastic weather shield.










I used an inexpensive accelerometer (www.digikey.com part number MSP1001-ND) to first measure the vibration in the door. I located the accelerometer just a few inches to the left of the door opening; an area subject to the most vibration from the speaker.

Next I applied the damplifier. This stuff is the thickest mat I've ever used, and was very easy to work with. 


















I also put the speaker pads in the door behind the drivers, albeit they were a bit higher due to this bar blocking the way. And of course I used about 5mm of modelling clay behind the mdf baffle to further decouple the driver from the door.


























Next I cut and applied the very thick pad of overkill pro (easily 3x as thick as the original oem mat), which appears to be a closed cell foam/rubber composite. Overkill pro is supposed to help reduce higher frequency rattles and noise. Using the spray which is similar to 3m adhesive spray, I was able to put the pad onto the door securely with no hassles.










Lastly, I replaced the stock carpet padding on my door with some rattle mat. 










All in all, I spent about 4 hrs to do both doors. Not bad. I definitely recommend having a sharp box cutter and some extra blades handy, as well as a pair of scissors. 

And here is a shot of the accelerometer mounted to my door:










So how effective was all this deadening? Let's take a look at what the accelerometer reported. Below is a cumulative spectral decay plot. In essense, it shows you the frequency AND time response on the same chart. 
Bear in mind the accelerometer is extremely sensitive, so there's quite a bit of extraneous noise that may not be audible.

Non-deadened response:










If you follow the time axis (z axis) you can see that at certain frequencies there's a very pronounced ridge indicating strong resonances and vibrations that continue long after the initial signal has stopped. The strongest one appears to be around 200hz, with not only the highest peak in the frequency domain, but the longest running ridge in the time domain indicating strong resonances in that region. 30hz to 60hz also appears to be problematic. There's also quite a bit of low level noise above 1khz.

After deadening:










What an improvement in noise above 1khz (albeit noise that may not be readily audible)! The ridge at about 200hz is almost completely gone as well. Below 100hz we see a noticeable reduction in energy, however still problematic. The results are actually a bit better than the plot would indicate below 100hz, as sealing the door also dramatically increases bass output in this region. However, I don't think any dampening product of this nature can completely elminate the strong vibrations below 100hz at this level of output.

Subjectively, I have to give Damplifier pro a big thumbs up. This is a very thick mat that's easy to work with and adheres well even in cold rainy weather (which I happened to be working in) and is odorless. It's obvious that it also has a dramatic impact (provided you seal the big holes in the door) of increasing bass output and almost eliminating all the audible rattles. Both Kevin K. and Dual700 had a chance to hear my midbass output and it was phenomenal.... enough to set the rear view mirror vibrating pretty hard.

As far as the speaker mat, I'm not entirely certain of it's effectiveness. It did change the sound a small bit, as in mildly reducing some haze in the midrange, but the effect was very subtle and could have been due to any number of other factors. Bear in mind though, that I could not locate the mat directly behind the driver.

The rattlepad and overkill pro though I have to say are quite effective. I could barely get my door panel back on, but audibly alot of the buzz and rattles disappeared.

All in all, I'm very happy with the results of my deadening project minus a few cuts and scrapes and sticky fingers


----------



## mathman (Jun 15, 2005)

Fantastic  

That's the first accelerometer test I've seen on a car door, so this is great info. I'm somewhat surprised how much was suppressed given the amount of material. I'm guessing to get rid of the last bit of bass resonance you need more mass in there. Still, very encouraging results.

My hat is off to you and the good people at Second Skin.


----------



## npdang (Jul 29, 2005)

It's very, very easy and cheap to do an accelerometer test of your doors. I used a full range chirp, but you could also excite the door with different kinds of signals to see what you get.


----------



## Weightless (May 5, 2005)

How many layers of the mat did you add? I would like to see how much multiple layers directly around the speaker helps with lowering the vibrations...

The accelorometer is a great idea. 

Rudeboy should add one to his sound deadening showdown...


----------



## demon2091tb (May 30, 2005)

Thanks Dang for the test, nice accelerometor test, i think you just set the new standard haha. I'd love to do one on mine as well, wanna give us a little tutorial for us idiots....

Anyway how is it possible to eliminate those 30/60/etc resonances, as right now i have plenty of midbass output, more than i probobly need, but on warmer days the resonances just go crazy around 60-70hz, anything below that and its wayyyy tooo significant and colors the music way too much.

What materials would actually allow this below 60hz?


----------



## npdang (Jul 29, 2005)

You can pickup the digikey part listed above for about $30. You can plug it into your soundcard and any MLS program with waterfall/csd plot will do it. I will include the accelerometer with the free DIYMA test setup that's going around soon. Unfortunately, I don't have the time to do a more in depth analysis of where more deadener would make the most difference, but it sounds like a great idea!

As far as eliminating resonances below 100hz... I think it's going to take alot more than regular mat to do that. You'd probably need alot heavier mods to accomplish that.


----------



## Medicineman (Apr 9, 2007)

Wow, great timing.

I have been working on dampening my truck before installing the new equipment. I "was" trying to decide if Overkill Pro would be worth the extra money and effort. You just convinced me it will be.

I am using Dynamat Extreme (got it for dealer cost when I suggested putting off buying amps until I could find a better price on dampening material ). It has the same specs as Damplifier Pro. Subjectively, it has reduced almost as much sound by itself as all of the old carpet, padding, and interior panels that were in the truck before. I am still amazed. It does have trouble with the lower frequencies, however. Most notably on large sections of unbraced sheet metal (of course). I drive a full size chevy blazer so there is a lot of sheet metal. The worst area for me is the cargo area floor. I may end up bonding a 1/4 inch sheet of plywood to it before installing carpet. Preventing the metal from flexing is the only way I can think of to reduce low frequency noise and dampening material will not do the job over large areas.

Thanks for the review (and the quality site in general)


----------



## zfactor (Oct 19, 2005)

great write up man.. nice little test there.. maybe deadening companies will take note lol...


----------



## POLKAT (Jan 10, 2007)

Bang for the buck, would you go with Raamat or Second Skin? No offense to Rick as I think his products are great. I am getting ready to deaden my Trailblazer's doors and seeing this review makes me wonder if I should go with Second Skin instead.


----------



## Whiterabbit (May 26, 2006)

bang for the buck, you cant beat raammat


----------



## dbiegel (Oct 15, 2006)

If someone is willing to do a comparative review of RaamMat, Dynamat Extreme, and Second Skin with that accelerometer, I think that would be a breakthrough in information for the car audio community. Right now, there's no real objective information out there on the sound deadening effects of these different products.


----------



## zfactor (Oct 19, 2005)

POLKAT said:


> Bang for the buck, would you go with Raamat or Second Skin? No offense to Rick as I think his products are great. I am getting ready to deaden my Trailblazer's doors and seeing this review makes me wonder if I should go with Second Skin instead.


they are both excellent products. ive used both and also dyn extreme. its hard to say which i liked best they all had positives and there negatives though. i will say if you spend the money you simply cant go wring with dyn extreme, but the best bang for the buck imo is prob raamat. with second skin being right in the middle.. all three are top notch and you wouldnt go wrong buying any of them


----------



## ErinH (Feb 14, 2007)

I already have 3 layers of 2nd skin. I just ordered a little bit of BXT & some Ensolite from Rick (great guy BTW). I'm curious to see the results of the ensolite more than anything.

IMO, I don't know how easy it would be to tell a difference _hearing_ the two alone. I think the only difference may be in installation. They both seem to be nearly the same product. I think it comes down to a preference. Ricks' products are a little bit cheaper, and after dealing with him in my recent purchase, I'll be a forever Raam Audio customer. 

I'll post up my thoughts on the ensolite addition later this week. I've got a set of Seas L18's coming in and hopefully the extra deadener & ensolite will help me get more out of them.


----------



## Rudeboy (Oct 16, 2005)

zfactor said:


> they are both excellent products. ive used both and also dyn extreme. its hard to say which i liked best they all had positives and there negatives though. i will say if you spend the money you simply cant go wring with dyn extreme, but the best bang for the buck imo is prob raamat. with second skin being right in the middle.. all three are top notch and you wouldnt go wrong buying any of them


I think the real quality hierarchy would be, from top to bottom, Damplifier Pro, Dynamat Xtreme, Damplifier, RAAMmat. All are very good, but both Damplifiers use a better quality adhesive than DX.


----------



## Rudeboy (Oct 16, 2005)

DOMN8R said:


> If someone is willing to do a comparative review of RaamMat, Dynamat Extreme, and Second Skin with that accelerometer, I think that would be a breakthrough in information for the car audio community. Right now, there's no real objective information out there on the sound deadening effects of these different products.


The problem with this approach is that you would an identical car for each sample - it wouldn't be practical to install, test, uninstall and then install the next product. I've been wrestling with this question for some time now and really don't see a good solution. I know the manufacturers will not make this information public because there is no solid standard. Many have done testing - some have even shown me the results, but publishing it will only hurt then as long as other companies are willing to post bogus numbers.

Standard acoustic loss factor testing in the lab might yield useful results, but even if it didn't cost $600 per sample to perform them, I'm not sure they can be controlled to account for all of the variables we run into with different products - density, thickness, existence of a constraining layer and its thickness, density and elasticity, etc. We can be really confident that an 80 mil product with a 4 mil foil layer will outperform a 40 mil product with a 2 mil foil layer, but by how much? How would two layers of the 40 mil product compare to one layer of the 80 mil?

What we run into is an infinite number of possible combinations spread out over every possible combination of temperature and frequency. I've been looking for some way to standardize these tests so that I could ask the manufacturers to pay to have their products tested. I've talked to some of the best testing labs in the country and some scientists that specialize in this stuff. So far it doesn't look good. 

This kind of thing is pretty easy for an OEM. They look at each part of the vehicle then test a variety of approaches. We're looking for a solution that will work everywhere when applied under very sub-optimal conditions.

I really think the best we can say is that for mats, superior adhesive and thicker foil will be the most effective and for liquids, who knows - elasticity and mass of the cured product?


----------



## Weightless (May 5, 2005)

Why not test with multiple sheets of sheet metal, maybe 18x24" with similar gauge of an average car door. Cut a hole in it to mount a 7-8" speaker in the typical fasion(mounting ring and maybe clay). Apply a piece of mat from each manufacture and test with the accelorometer to see which product dampens the best. Then add multiple layers to test the theory of more is better.

You can use one sheet without any mat on it to compare to.

Does this sound like a good test? I think I would be willing to chip in a few bucks to help fund the test...


Justin


----------



## Rudeboy (Oct 16, 2005)

SQ_Baru said:


> Why not test with multiple sheets of sheet metal, maybe 18x24" with similar gauge of an average car door. Cut a hole in it to mount a 7-8" speaker in the typical fasion(mounting ring and maybe clay). Apply a piece of mat from each manufacture and test with the accelorometer to see which product dampens the best. Then add multiple layers to test the theory of more is better.
> 
> You can use one sheet without any mat on it to compare to.
> 
> ...


That really wouldn't be much different than the Oberst bar ALF test, just cheaper to do and a good bit less accurate. Once you start cutting holes in the sheet metal you introduce all sorts of variables.

Then the question becomes one of standardization. Do we use samples of equal area? Equal mass? The problems really come in because these products aren't similar enough to compare effectively. 

Something that really stuck in my mind, said by a guy who develops vibration damping systems for the aerospace industry was: "You aftermarket automotive guys just slap stuff on until you get things as dead as you want them." I honestly think that all we can do is use the research that has been done on vibration damping, throw in durability considerations, evaluate value and just go too it. I don't believe there will ever be a definitive empirical answer and I'd be very concerned about using incomplete tests to suggest there was. It looks lie the best we can do is say: these products are pretty good for this purpose, these products aren't.


----------



## OldOneEye (Jun 16, 2005)

SQ_Baru said:


> Why not test with multiple sheets of sheet metal, maybe 18x24" with similar gauge of an average car door. Cut a hole in it to mount a 7-8" speaker in the typical fasion(mounting ring and maybe clay). Apply a piece of mat from each manufacture and test with the accelorometer to see which product dampens the best. Then add multiple layers to test the theory of more is better.
> 
> You can use one sheet without any mat on it to compare to.
> 
> ...


I would venture to guess you would have a hard time finding a flat piece of metal in a car that big outside of the roof.

I guess the main ways these products do what they do is by absorbing sound, adding mass, and stiffening the panel. But people buy on other factors that we would have a hard time measuring (so 2 times the labor to do two layers of a product half as thick (mass I would guess). Is that a good deal?).

If I were conducting a test, I would go to a pull a part type of junkyard and buy a few doors of the same vintage Ford F150 (the top selling vehicle in the US for a LONG time). That would minimize cost. Then I would go at it and measure. You can make it where all the doors are cleaned in the same way, so a ton of variables can be controlled.

juan


----------



## illnastyimpreza (Oct 25, 2006)

wow thats awesome ! I gota get one of those something-ometers... 

I actualy just finished installing some second skin sludge to my GF's Subaru legacy doors....I used half a gallon for both doors. what an improvment !

second skin makes some AWESOME products....

now.... how do I go about getting some donated to me for "Testing" ???


----------



## BlackLac (Aug 8, 2005)

was the test done before you applied the overkill pro or did you just apply the overkill pro over top the scope? looks like its attached to the damplifier.

edit: ask him to send some luxury liner and re-test, that stuff is THICK!


----------



## raamaudio (May 4, 2005)

Second Skin makes great products

Rick


----------



## Whiterabbit (May 26, 2006)

Rudeboy said:


> Then the question becomes one of standardization. Do we use samples of equal area? Equal mass? The problems really come in because these products aren't similar enough to compare effectively.


I just sent you an email about this 

all we have to do is determine what _material_ property affects material suitability. (and cost IS a material property! ) Easy enough, we just backtrack the performance we want to the material properties that affect them, then measure the material properties!

to make the simplest analysis, we compare two material properties on an XY chart and graph data points, one point per material. we end up with regions of materials, with groupings. Materials that are in the same region have the same performance, given just those two material properties.

a firm basis for objectively comparing anything we relate to car audio


----------

