Objective CLD (sound deadening) Testing Results

[TOOSTUBBORN2FAIL]

I got the go ahead to post this.

The test rig is a baltic birch box, with a pair of Hybrid Audio Technologies L6SE's bolted to one side, and an 12"x12" 16ga steel sheet clamped down around its outer half inch. This leaves an area of 11"x11" exposed. The back of the speakers are covered by a second box, to prevent any noise directly from the speakers from reaching the mic.

The mic is a Dayton Audio calibrated usb measurement microphone, and it is run through REW. All measurements are taken with sweeps in order to get both frequency response and decay plots. All measurements were taken with the panel at 77 degrees F, using an ir thermometer. All measurements include a bare metal measurements and a treated metal measurement. The treated metal measurement was taken with 28% coverage, and the test pieces of deadener were die cut to ensure consistency.

Products were also heat tested, and my summary includes my explanation in how that played into effect. Basically anything that had even a hint of risk of failing, got dinged. Anything that showed a history of failing or failed heat testing miserably flat out failed.

The margin of error on these tests is +/- 0.75db. I came to this conclusion doing multiple tests of several products, sometimes months apart.

I have no vested interest in any company. Some samples were provided by other car audio enthusists. Others were provided by sound deadening companies. There were company provided samples that did well and ones that did horrible.

This is the list of the majority of tested products and their results, in raw form.
http://www.diymobileaudio.com/forum/...-post1723.html

This is the results for Silent Coat products.
http://www.diymobileaudio.com/forum/...-post1724.html

And this is the final summary for the time being.
http://www.diymobileaudio.com/forum/...-post1725.html

[Ashikabi]

Thanks

[TOOSTUBBORN2FAIL]

No problem. I have one more post to add to this, probably monday, that explores different installation ideals, ie 25% vs 100% coverage.

[DAEMANO]

@TOOSTUBBORN2FAIL

Incredibly thorough man. Great, great work!

[TOOSTUBBORN2FAIL]

So, as everyone knows, I had to stop testing for the time being. I also had to sell the speakers used in the test rig. I knew I couldn't possibly finish all the brand comparison's in time, but I still wanted to test a few last things. Being that it would not be fair for me to pick and choose which brands to test, I instead testing install methods. 25% vs 100%, stacked double layers vs opposed side double layers, multiple small pieces vs one large piece. I needed to use a product that I still had enough of to do multiple tests, the only product with enough material for that was SDS Tiles and SDS Sheet. I know, SDS Sheet was not included in the product comparison test, but I had no other material in quantities large enough to use for the purpose of this testing.

Just to clear the air, I was extremely stressed out on the day I did this, so I screwed up on this run of testing, and closed out REW without saving the files. Therefore, I only have the individual frequency response plots and waterfall plots saved. Rton20s helped me out by overlaying the plots so the comparisons are easier, although the plot names are jumbled. That is entirely my fault. The other thing you'll notice is I tested at a much higher level. Aside from that, all testing was done as normal, at 77 degrees, with all noise sources as quiet as possible. Never realized how long my fridge runs for until I had to wait for it to stop.


Lets start with 25% vs 100%. I tested this with SDS CLD Sheet. It is advertised as a corrosion preventative treatment for camper vans, and is recommended to be used at 100% coverage. It is the same butyl as CLD Tiles, but thinner with a thinner constraining layer.

Bare Metal Frequency Response - Peak Amplitude 114.2db
28% Damped Frequency Response - Peak Amplitude 103.0db




Bare Metal Frequency Response - Peak Amplitude 114.2
100% Damped Frequency Response - Peak Amplitude 98.0db




So there is a 11.2db drop in peak amplitude with 28% coverage. There is a 16.2db drop with 100% coverage. So, to treat 1 square foot, you would spend $0.85 for the first 11.2db, and $2.20 for an additional 5db.



As an aside, I would now put CLD Sheets just above Dynamat Xtreme for those wanting the lightest weight effective damper out there. I know this isn't a direct comparison, however, the performance is as good, and it is lighter.



Moving on. SDS Tiles, 28% vs 56%. This test used a single 28% coverage piece vs two 28% pieces double layered on each other.

Bare Metal Frequency Response - Peak Amplitude 114.2db
28% Damped Frequency Response - Peak Amplitude 98.5db




Bare Metal Frequency Response - Peak Amplitude 114.2db
56% Double Layer Damped Frequency Response - Peak Amplitude 96.8db




So, 28% coverage with CLD Tile gave a 15.7db reduction in peak amplitude, vs 17.4db for 56% coverage using two 28% coverage layers. Your first 15.7db will cost you $1.78, while that additional 1.7db will cost you another $1.78.


Moving on. I have long held a belief that if you are intent on double layering, that put one layer on each side of the metal would be better than putting two layers on one side. Well, I was wrong. This tested that theory, using 28% coverage on each side of the panel In fact, the results are damn near identical.

Bare Metal Frequency Response - Peak Amplitude 114.2db
56% One layer per side damped Freq Resp - Peak Amplitude 96.8db




And here is an overlay showing 28% coverage, vs both forms of 56% coverage.


As with double coverage, you would get your first 15.7db for $1.78 and your additional 1.7db for another $1.78.


I also ran a test just to see what would happen. I ran a 28% vs 120% test using CLD Tiles. The 20% was layered on top of the first layer. My test rig panel measured 10"x10", and CLD tiles are 6"x10", so I put one dead down the center, and cut one in half, covering each uncovered edge.

Bare Metal Frequency Response - Peak Amplitude 114.2db
120% Damped Frequency Response - Peak Amplitude 95.1db*




And for fun, 0% coverage vs 28% coverage vs 120% coverage.


So in this case, your first 15.7db comes at a cost of $1.78, while an additional 3.4db comes at an additional $10.94.

*Now, there is a catch. If you look at the 120% graph, you'll notice the original peak is actually down more like 24.2db, and there is a new peak lower in frequency. That peak has always been there, but it was always secondary to the largest peak. I have a hunch that secondary peak may be due to the speakers themselves, as you can see that peak in every other test I've done, and it never changes very much, which you can tell by looking at the waterfall plots. None of the products can stop that particular peak from ringing. Even so, if we ignore that peak, you would still be getting the first 15.7db for $1.78, and the next 8.5db for $10.94.


On to the last test. I've had a hunch for a while that using one large piece of material was more effective than using a bunch of small pieces. This test proved that theory correct. In fact, it actually blew me away on how much of a difference it makes. If you cut your pieces too small and use a lot of them, instead of fewer large pieces, CLD actually stops working as a CLD, and works more like a mass loading product. To test this, I cut up a 28% coverage piece into 4 equal pieces, and placed them around the center of the panel.

Bare Metal Frequency Response - Peak Amplitude 114.2
28% Damped Multi Piece Freq Resp - Peak Amplitude 108.4db



And here is 0% coverage, 28% coverage, and 28% coverage split into 4 pieces.


As you can see, you go from a 15.7db reduction in peak amplitude with a single piece of CLD Tile, to a 5.8db reduction if you cut that same size piece into 4 pieces. It also rings for much longer, and maintains its high Q frequency response. Bottom line, don't cut your cld pieces if the panel you are treating is 75% larger than the piece of cld you are using.


That's it guys. Speakers are out and for sale. At some point, I will start again, with a new rig and better results. Hopefully sooner rather than later.

[DAEMANO]

@TOOSTUBBORN2FAIL

Oh man! This is among the best content on this site. Seriously man, if you love doing this kind of testing as much as it seems you should have a Youtube account and a Patreon. This post should be stickied, because it dispels a lot of assumptions that apparently have turned out to be incorrect. Great...GREAT test!

[TOOSTUBBORN2FAIL]

Thanks. I actually really do love this stuff. Unfortunately there are some life events preventing me from doing anything else at this time, but I do plan on starting again whenever those issues resolve and putting out even better info. I will likely add a youtube channel at that time, along with testing at multiple temps, since varying temps affect the performance of each product as well. For these, I had to do each test at 77 degrees, since it wasn't feasible to heat and cool the whole house to get measurements at different temps.

The next test rig will be self enclosed, which will both lower the noise floor, and allow the varied temp testing.

[fumanchu1]

Thanks bud that is some extensive research right there

[johan]

These tests are amazing! Damnit, I just finished a complete treatment and that last test about cutting the pieces down would have been REALLY helpful to know. I had a feeling that was true, but seeing actual empirical evidence... damn.

[Ashikabi]

Excellent stuff, you're gonna save me a ton of money and weight