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Sound Deadening (CLD) Testing

779K views 2K replies 210 participants last post by  TOOSTUBBORN2FAIL 
#1 · (Edited by Moderator)
So like many other people, I'm tired of wondering what CLD ACTUALLY works best. So I've decided to test a whole spectrum of them, using an accelerometer, so this can be put to rest. This will take between 1-2 months to start, but may be drawn out over time if people want continuing results from new products, etc. Once I have the test rig set up, it wont be that hard to test.

As of right now, I plan to build a box out of baltic birch. It will have two removable baffles, both secured with 10-32 screws, and hurricane nuts. The front baffle will hold two speakers, which will remain unchanged throughout the testing. This will be HAT L6SE's. There will be two front baffles, one completely sealed, aside from speaker mounting holes, and one with two 2" vent holes. The reason for this, is that a sealed box will cause different levels of vibration than one that is just measuring structural vibration, and I want both measurements.

The back baffle will be 22ga 12" squares of mild steel. There will be a new piece of steel for each different CLD. The reason is, removing this stuff could result in bends, and that could change resonant frequency of the baffle. So each CLD test will get its own piece of metal, and each will have before and after measurements, so that deadener effectiveness can be seen as a percentage. I will also post the frequency response of each test, if possible (I need to check one what kind of output I can get from my O-Scope, more on that by friday). Each panel will be bolted on at a set torque with a calibrated torque wrench, to keep that from being an issue. The piece will have a 1/2" perimeter to be bolted down to.

Each CLD piece will be weighed, measured, and photographed multiple times pre and post installation. I may also take video of each test. Samples will all be 6x6" squares, just a tad bit over 25% coverage. Testing will be done indoors, and will be temperature controlled.

I'm open to durability testing, but using the oven is out. New house, and not quite ours yet, means thats not going to happen. I have a torch, but thats a little inconsistent. It does get ridiculously hot here in the summer, I could save all the pieces, then leave them out when its 110 degrees for a week or so.


Once I've gone through the testing to "rank" the deadeners, I will move on to some intall technique tests/alternative deadening techniques tests. Things such as seeing what kind of differences to expect going from 25% coverage to 50% coverage, etc. I'd also like to test using small pieces vs on large equal area sheet. I've seen it suggested that small pieces randomly spaced works just as well, I'd like to prove or disprove that. Then I'd like to test bracing, and bracing+deadening, etc.


If anyone has an input, feel free to let me know. I'd like to get this issue settled.

If anyone wants to donate products, they are more than welcome, I'll post in the first post what I have, and whats been donated, and by who, unless they wish to remain anonymous. All I ask is that pieces donated are 6x6" squares or larger.

I've updated what people might be able to send so far. I want to make sure no one feels any pressure or rush, the soonest I forsee being able to start actually testing is the beginning of May. When I get products in, I'll move them to the corresponding area. I will also start to build the test enclosure this weekend.


Dynamat xtreme - 1 12"x12"
GTMat Pro 50 Mil - 1 12"x12"
GTMat Ultimate 80 Mil - 1 12"x12"
GTMat 110 Mil - 1 12"x12"
GTMat Onyx - 1 12"x12"
Alphadamp - 1 10"x14"
SDS CLD - 1 6"x10"
Stinger Road Kill Pro - 2 6"x6"
Lightning Audio Deadskin - 1 8"x8"
StP Bomb - 1 sheet
StP Gold - 1 sheet
StP Silver - 1 sheet
StP Vizomat - 1 sheet
Peel N Seal - 1/3 Roll

Things that are on the way or have might soon be on the way

Fatmat
second skin damp pro
edead
possibly some cascade V-2
possibly some knu concepts stuff

That leaves me wanting for the test

cascade vmax
maybe some raamat
 
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#172 ·
Just to try it, I measured response with the mic, without the metal, and with the metal (butyl rubber still on it). I also took a measurement including phase, with and without. For without metal measurements, the clamping ring was still bolted and torqued, just not with the metal.

Without metal

With metal

Without metal with phase

With metal with phase
 
#174 ·
I thought so too, but im not 100% confident with the phase measurements with the metal on. It seemed to struggle to measure phase with the metal, but had no problems without it. Im going to repeat the tests today and see what I get.
 
#176 ·
I think he is just testing how the mic will react to strictly the drivers with no additional resonance from the metal. I believe the bare metal will still become the "baseline" measurement.

On a side note, I placed an order from Knu Konceptz today, so we will have some Kno Knoise and Kno Knoise Kolossus Edition to add to the testing.
 
#177 · (Edited)
Dustin is right, theres definitely a reason for testing without the metal. I wanted to get a measurement without it in place, one with it, and another set of both after I isolate the back of the speakers from the room. That way it gives me a better idea of the limitations of the mic due to bleed through. Im also still on track to have the accelerometer up and running this week.

Bare metal will absolutely still be the baseline.



Dustin, let me know when it comes in, I'm looking forward to comparing it to the others.
 
#178 · (Edited)
TooStubborn,

More ideas that you probably have already considered but maybe will help. You seem super thoughtful about your testing which is commendable. However, any rig you build will not be perfect and can always be improved so don't let it keep you from starting to run tests. You may find that some things that seemed critical are not and other things you never considered will be problematic.

Ideas:
1) In any testing calibration and baseline are key. Even if the test system is flawed you will document the flaws and they will apply to every test.

2) If you are able, the best thing you could do is to EQ the mic for a flat response. This is probably the single biggest source of error. What is the peak to peak voltage you are getting out of it with an 80 - 90 db source signal? Do you have the response curve from the manufacturer? Get the mic response flat and then the peaks, etc, even at resonance will not overdrive your mic. If you do experience overdrive back off the gain a bit.

3) You mention phase measurement - is there any reason you can't just use the source signal against the measured signal? I don't even know of any better method because all methods involve a transducer whether it is the actual speaker or something to measure what the speaker is doing. I was always taught to measure the two signals and compare them.

4) Isolating the back of the speakers should be simple. Close them in with MDF and stuff them with insulation. You will not get it to zero but it will be negligible. Out on the highway there will be a variety of entry points for road noise that are much louder.

It's OK to get it reasonably tight then run a batch. It will show you some important things and then you can decide how much you need to improve the test setup.

Greg
 
#179 ·
TooStubborn,

I just thought of something that might be an awesome idea. In the lab we always use the best practices to make our tests as accurate and clean and reproducible as possible. I think we are all agreed on that.

But as far as an input sound source, what if you took a super flat microphone, strapped it to the underside of your car, and went out and measured a variety of road noise samples?? You could do concrete freeway, blacktop highway, a bridge, a tunnel, whatever. Tone sweeps, etc, should be done also but we are trying to dampen road noise. And road noise has unique signature. Of course it would be different depending upon the vehicle size and tires, etc. but any sample would be a good test medium.

My 2 cents.

Greg

PS I can make some sample if you like.
 
#180 ·
Here is a free tool that may make this task easier. It will help identify the difference between two audio signals and makes mic calibration a non-issue as long as you are not overdriving the mic or the digital to analog converter inputs.

Audio DiffMaker

I have used this company's flagship product, Praxis audio measurement software for more than a decade. Bill Waslo, founder of LIberty Instruments, was one of the legends of DIY audio 20 years ago and published multiple articles in Speaker Builder and AudioXpress magazines. He had an earlier audio measurement package that was very DIY friendly in the early days of computer based speaker design software. It was cheap and accurate but unfortunately based on DOS and it faded from use as Windows took over the world. Praxis was pretty expensive when I bought the package that included a calibrated mic and USB amplifier and audio interface box. You won't need any of that to use Audio DiffMaker.
 
#181 ·
Any news on this?
 
#182 ·
I've been doing a lot of work, but mostly silent, as I've been trying to get together money to pick up a better accelerometer. But it doesn't look like that's going to happen. Just don't have the budget right now. The problem with the current accelerometer is it doesn't have the signal to noise ratio to pick up the full range from 20-500hz. I was thinking of eq'ing the response to get it to work, with a note in the results that that had been done, but the speakers, amp, and power supply cant handle it. From 90hz to 70hz the response drops 30db. I have about a 20db range the accelerometer will pick up. I would need 20db more head room, but that would put everything I have way past its safe range. At the least, I would need a subwoofer, and a better power supply.



That said, testing has actually begun. I've been dialing in the setup for the last weekend, and actual final results will be coming tomorrow. Unfortunately, the microphone is the only measurement device I have for this at this point. It will be placed as it has been shown in the pictures, however it now has a jig that holds it in the same place every time. I'll be using the Omnimic mic, and REW for results. I'll have both frequency response, and waterfall graphs. REW is soo much easier to overlay graphs than Omnimic is.

I will be starting with the asphalt based products, only because they clean off of the metal the easiest. And with that...........I will now give my SUBJECTIVE opinions on the products, based on cutting them out, handling, etc. Keep in mind, this is only subjective, and not based on results from testing with the mic.


Peel N Seal - One of the thinnest feeling constraining layers. Aluminum seems to be coated, I'll follow up with a polish test. Definitely has a smell to it that butyls don't. My wife knew exactly when I opened the box. Has a good backing paper. Cut relatively easily.

Alphadamp and SDS CLD Tiles - The butyl seems similar in both cases. The aluminum is also thick in both, just a tiny bit thicker on the alphadamp. That said, I expected them to both cut similarly, and especially with alphadamp being 20mil thinner overall. That said, alphadamp was significantly more difficult to cut. I'm going have to ask what grade of aluminum brands are using now, because that's the only thing I can think of that would make it that much harder to cut. Both these products are two of only 3 products that could support themselves while just holding the corner of the sheet.

Dynamat, Stinger Road Kill Expert, and GTMat Onyx - All three are very similar as far as butyl consistency. They all have the most sticky butyl of any of the products, almost oozing. The backing on dynamat and road kill is paper based, and sticks well. The onyx backing is a pretty thick plastic, and sticks well. All cut similarly well.

GTMat 50mil, 80mil, and 110mil - All three had thin constraining layers. There has been some speculation by some that the constraining layer is not actually aluminum. I will be testing this. It seems very similar to the Peel N Seal layer, and it is definately coated in something. The backing paper is not up to par with the others, its a very thin plastic layer, but at least with the samples I received, it doesn't seem to stay in place very well.

Lighting Audio Dead Skin - By far the lightest feeling product in the test. Also seems asphalt based. Also has the worst backing paper, it seems to want to fall right off. Its possible that this sample is old, but I'll test it anyways. Looking around, I couldn't find any specifications for it anywhere.

STP Vizomat - This is an oem type free layer damper. It was very easy to cut. Plastic backing, that sticks well. The website says its a bitumen product, which is a form of asphalt, but there is no smell.

STP Gold and Silver - Both products are an butyl products, gold having both a thicker constraining layer, and butyl layer. It seems very stiff for the constraining layer thickness, and has an embossed pattern in the constraining layer.

STP Bomb - This is the thickest product of the whole group. It is also the third of the products that can support its own weight by holding the corner. It also seems very stiff for the constraining layer thickness. This is also a mastic-bitumen based product, but like vizomat, has no smell.

Knu Konceptz Resonance Control and Kolossus - Both products are butyl based. Both have decent back papers, and seem to cut well. I haven't had much time to play with either, but I have a large amount of both, so I'll post more as I get a better impression of them.
 
#183 ·
Thanks for the update Chris. Sorry I haven't really been around to help. Seems like the last few weeks have been crazy, and this weekend will be no different. I might have some time in the evenings starting next week, just shoot me a text when you might be working on this and I'll do my best to swing by and help.
 
#184 ·
Thanks Dustin, its been pretty hectic here too. Just finalized the refinance on the house last week, drama at work that could lead to termination for some people for breaking certain laws, and trying to get ready for promotional testing and interviews. Seems like when one thing ends, another starts up. To top it all off, I started riding to work again this morning, and lost a shoe to a pitbull on the way. I was lucky my wife mad me wear my skate shoes, because if I was in running shoes, it would have ripped me off the bike. Found out later animal control put it down after it killed another stray.
 
#185 ·
Great update Chris! First impressions are nice since most people order these online and don't get to handle them. Very interested to see the results.
 
#186 ·
So, my calipers and micrometers are eluding me tonight, (probably at my sister in laws), but there is at least one deviation from published specs so far. This one is so blatant that its visible. After reading published specs for Knu Konceptz Kolossus, I had to re-look at some things. Mostly, comparing its constraining layer to Alphadamps. Both advertise as having a 10mil thick aluminum constraining layer, but Alphadamp was significantly more difficult to cut. I went back and cut a small sample to tear apart and measure. Before removing the butyl from the aluminum, I tried flexing both, and had my wife do the same. The conclusion was both of us thought the Alphadamp was much stiffer. I then started pulling the butyl from the aluminum (took about 10 mins per sample, for about a 1" square section). The Alphadamp is definitely thicker than the Kolossus. Since I don't have a way of objectively measuring until tomorrow, I'll just say for now that it seems like the Alphadamp aluminum is 3mil thicker. If Alphadamp's aluminum is truly 10mil thick, that would put the Kolossus aluminum at 7mil, which is the same as what Knu advertises its cheaper (20% cheaper) Resonance Control line as having.
 
#187 ·
Interesting find. And I had high hopes for Knu, since they do seem to be a good value. If you don't find your measurement tools, let me know. I believe I still have mine kicking around the garage somewhere.
 
#188 ·
Ok, got my calipers. Alphadamp measures between 9.5-10.5mil. Stp-atlantic's Bomb measures 4mil (stated thickness is 100 microns, or 3.9mil). Kolossus measures 7mil, BUT that is with a protective plastic film covering the aluminum. I couldn't peel it off at work very well, but that film is between 1-2mil thick. When I get home, I'll get the film off and measure just the aluminum. Remember, stated thickness is 10mil.
 
#190 ·
Definitely an interesting find! I would definitely like to know the difference between the standard Kno Knoise and the Kolossus. Are they both using undersized constraining layers? Do they both use the same constraining layer with the Kolossus simply using a thicker adhesive layer? (7 mil is the stated thickness of the standard Kno Knoise after all.) And of course the most important question, how do they perform? Really looking forward to the results of the testing.
 
#191 ·
So they are definitely using undersized constraining layers on both products. I haven't been able to get the plastic layer off, next step is to try chemicals. Its very slick, and the best tweezers I have won't grab it firm enough to peel it off. So, with the plastic film still in place, the Kolossus constraining layer averages 7mil thick, instead of the 10mil thick advertised. Resonance Control averages 4mil thick with the plastic film in place, instead of 7mil thick as advertised. Keep in mind, they are claiming the aluminum layer is 7mil and 10mil thick respectively, saying nothing about a plastic film.

I'm going to try a couple of things tonight to get the film off and get a final measurement, and then email them, but I'm not sure I'll get an answer. I know both myself and rton20s emailed them about participating in the testing, and never got a response.
 
#192 ·
Plastic film is cheap so I can see using it to protect the aluminum; it obviously doesn't work as a constraining layer and should not be used to help bring up the mil for advertising purposes.


How is the accelerometer coming? I have been thinking about other ways to measure the flex. There are distance measurement photo eyes, or something I work with a lot is a cam/spring with an analog sensor. Not sure how accurate the readings would be with a regular DMM, but just wanted to throw out a couple things I've been thinking about.
 
#193 ·
Yep, its not that the film is a problem, unless they are padding their numbers with it. But even with the film padding the numbers, they're still 30% and 43% off of the numbers they claim for constraining layer thickness. I'm really curious if they'll respond to a query about that, and what it is they'll say. Based on published specs, it theoretically should be a front runner, and rton20s purchased some to test after trying to see if they would donate a sample for it.


I posted a few posts up about the accelerometer, but basically the one I have now isn't going to be good enough. There are two ways to fix it, replace it, or eq the response, as GOYOP and my dad had suggested. Unfortunately, some things fell through for my wife, so I'm not able to pursue either option, as eq'ing the response enough to work puts the power supply past its abilities, and even if it was up to the task, it would be putting the speakers significantly past the safe point, both thermally and excursion wise. I would need a high excursion sub to get it to work.

At this point, I'll be using the mic, as Jazzi did in his project log, just in a more controlled environment. I'll have to get both frequency response of the bare metal, and damped metal, and waterfall plots of both. I'll have the first set of results to post tomorrow. I wont be able to test friday as I have testing for a supervisor position, but I will be testing sat and sun as well. I may have some raamat coming, if so that will be the last of the products to be installed on the roof of my car for long term heat testing.


Do you have any links or search ideas for the alternate measurements? I'd like to still look into it (who knows, I may get the position).
 
#194 ·
Update,

KnuKonceptz Kolossus - Constraining Layer thickness, no plastic film - 4mil - Advertised as 10mil

Knukonceptz Resonance Control - Constraining Layer thickness, no plastic film - 3mil - Advertised as 7mil

I'll prepare an email tomorrow morning.
 
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