The testing and results below are all from an independent enthusiast, Chris Purdue, who is on his own journey to find out what the best products are in the sound deadening market. Chris is a high-end car audio enthusiast, just like a lot of you reading this page, and has been so for over a decade. He has years of experience, and has a vast understanding of audio and how it works. This journey of his started years ago on the diymobileaudio forums. His previous testing can be found there. On his new test rig (which we will update this page with info about as soon as we can get to it), his new ongoing testing and its results can be found on his Facebook group named “The Deadening” (link below). The following data is all from this group, posted by Chris. If something about the article contradicts the data he has published for the world to use, please, let me know as it is nothing but a simple mistake. We are just here to help those interpret his data.

As of the publishing of this article (November 18th, 2021), these are the products he has tested on his new test rig.

So, before we dissect the data, we need to understand how these tests were done and what the data means. The first thing we need to go over is the test rig itself. The test rig is essentially two sealed enclosures with one shared wall separating them. The first enclosure is plain. Nothing about it is different from a standard sealed enclosure for a speaker. But the second enclosure has a removable metal panel that acts as the wall for the far end. Installed into the dividing wall is a speaker. The rear of the speaker fires into one enclosure. The front of the speaker fires into the second enclosure. A microphone placed just outside the metal panel measures the frequency response that the combination of the speaker firing into the enclosure with the resonant metal panel creates. This measurement is done before and after a Constrained Layer Damper is applied to the metal panel. This gives us the before and after data and gives us an idea of how the CLD affects the panel. We can measure frequency response, as well as decay of the resonance. The two are typically correlated, but decay, while being more telling, is much harder to interpret into easy-to-understand numbers. So, for now, we are going to stick with frequency response. The frequency response will have a peak in the frequency response at the resonant frequency of said metal panel. In this case, that peak is around the 100hz area, which is also typical for a car door. We want to focus on how much reduction in amplitude this peak has to determine how effective the tested CLD is. I will include a link to Chris’s walk-through/explanation video once he posts it. As of today, (November 18th, 2021), there is no video of it.

The Decibel scale is measured logarithmic instead of linear. Every 3-decibel change, the energy is doubled or halved. If you have a speaker playing something at 85dB, twice the amount of energy is needed to hit 88dB. You will need twice the amount of power applied to the speaker or twice the number of speakers to achieve the 88dB. If you double the number of speakers and double the amount of power, that would be a 6dB addition. 50 decibels is NOT half as loud, or half the energy of 100 decibels. Pretty simple, right? Good. Let’s recap with bullet points real quick just in case.

**. The decibel system is logarithmic, not linear.**

**. 3dB up is twice the energy. 3dB down is half the energy.**

**. 50dB is NOT half of 100dB. 25dB is not half of 50dB.**

**. 97dB is half the energy of 100dB. 103dB is 2x as much energy as 100dB.**

The rating system is simple. A CLD is supposed to do one thing and one thing only. Reduce resonance from a panel. So, while it’s the main focus, we will also be including a price to performance rating to give an idea of how products compare to what your dollar gets you. This price-to-performance rating is simple. The price per square foot of the product multiplied by its effectiveness in comparison to ResoNix.

Example: If ResoNix proves to be 2x better (3db difference) than another product, we take the price per square foot of the other product, and multiply it by 2. If this product costs $6.50 per square foot, and ResoNix costs $8.20 per square foot, we can now value the price to performance at $13 for this other product. While it may be cheaper, its not as good of an overall value as ResoNix

**Spoiler alert:** ResoNix is currently the best independently tested product on the market. And frankly, it wasn’t very close either. We expected this since our goal was to make the best performing product, hands down. Still, since it performed so well, we will use the ResoNix results as the reference.

How we are determining the Resonance Control rating is pretty simple. As you can see in the graph below, ResoNix reduces the peak of the panels resonance by 17dB. We will reference the performance of every product to that and use the fact that every 3db is half or double the energy.

How we are determining the price to performance is even simpler. Based on the math above, we figure out how much of another product (in dollar value) it would take to achieve the same performance as one square foot of ResoNix CLD

So starting off, you will see in the picture below that the panel was tested before each time a new CLD was tested to ensure that nothing was off. Here are all of the “before application” measurements. No real variances, which obviously is good.

**Since all of the “before” measurements are very similar, we will use one to keep it simple.**

First up, ResoNix CLD Squares. As you can see in the before/after measurement, panel resonance goes from 106.5dB to 89.5dB, a 17dB reduction. As mentioned earlier, this is going to be our reference. So from here on out, if something has a 3db difference from ResoNix, that would be half or double as effective.

Next up is the Kleenex of sound deadener, Dynamat Extreme. This is the most popular product for aftermarket automotive use worldwide, and they have been around for decades. Looking at the measurements, Dynamat Extreme drops the peak in the resonant frequency from 106.5dB to 98.5dB. An 8dB reduction in the resonance of the test panel. ResoNix being at a 17dB reduction in the test panel, is 8x as effective as Dynamat Extreme per given amount (9dB more equates to 8x the amount of energy). So, for every square foot of ResoNix CLD Squares, you would need 8 square feet of Dynamat Extreme to, in theory, yield the same result. We were able to find Dynamat Extreme online for as low a $4.65 per square foot. This generates a price-to-performance of $37.20 vs. ResoNix $8.20. To get the same end result as ResoNix, you would be paying 4x the overall price and doing 8x the work overall. This is not a good value.

Up next is 3M’s EPM. This is a new product that is different from traditional Butyl/Aluminum CLD’s. Its purpose is to be extremely light yet practical. The downside is, you pay a premium for the lightweight for average performance. We are leaving the ResoNix CLD measurement visible to use as a visual gauge, but remember, another product being in between the “before” peak and the ResoNix measurement does not mean the other product is half as good. Every 3db difference is 2x the energy. 3M measures at 96dB (we are rounding to the nearest half dB in favor of the product to make this easier) vs. the Before Measurement of 106.5dB. 10.5dB is the amount of resonance reduction we have. 7db less than ResoNix, making ResoNix about 5x as effective per square foot. We were able to find this product for as low as $8.20 per square foot. We can calculate that, in theory, you would need to spend $41 to get enough of the 3M product to achieve the same result as 1 Square foot of ResoNix CLD Squares. Another spoiler alert is that this is the worst value product in the entire test regarding resonance reduction.

Next up, we have a recently popular product, Kilmat 80mil. This has become very popular among car audio hobbyist groups and pages as a good budget option. Well, let’s look at the data to see how true that really is. Looking at the graph, Kilmat 80mil reduces the resonance peak from 106.5dB to 98.5dB. The same reduction as Dynamat Extreme, but Dynamat Extreme also lowers the resonant frequency of the panel vs. Kilmat 80mil. From this, we can assume that Dynamat Extreme is heavier than Kilmat. When looking at two products that reduce the resonance amount equally, we would then determine the better performing product by picking the one which moves that peak outside of our desired passband the most. In this case, it would be Dynamat Extreme. Now comparing to ResoNix CLD Squares. Since this is also a 9dB difference, ResoNix is 8x as effective per given amount vs. Kilmat 80mil. Kilmat 80mil comes out to $1.78 per square foot, so doing the calculation, we get a price to performance value of $14.24 to, in theory, achieve the same result as a single square foot of ResoNix CLD. 8x as much would need to be applied. More work to apply, more cost overall to achieve a given amount of performance. This, while seemingly low cost, is not a good value. Remember, subjective reviews on the internet are typically not a great source of accurate information.

Moving on, we have the slightly more expensive big brother of Kilmat, Noico 80mil. These products are both made by the same manufacture with similar formulas. The Kilmat is just a watered-down version of Noico, so let’s see what the Noico 80mil can offer. The graph shows a 9.5dB reduction (from 106.5dB, to 97dB) in the resonance peak. Definitely better than the Kilmat. Also, it lowers the resonance frequency lower than Kilmat. Looking at this, Noico is definitely a much better performer than Kilmat. Now comparing it to ResoNix. ResoNix lowers the resonance peak another 7.5dB lower than Noico. This equates to ResoNix being 5.62x more effective at reducing resonance in a given panel. Noico can be found for as low as $1.97 per square foot. Price to performance vs. ResoNix CLD Squares, you would spend $11.07 to get enough Noico to, in theory, be as effective as ResoNix. 5.62x the amount would need to be applied. This is also not as good of a value, especially when you consider the extra work required to apply all of that additional product.

Next up is NVX 90mil. This reduced the panel resonance from 106.5dB, to 95dB, an 11.5dB difference. Not bad. Let’s see how it compares in value to ResoNix CLD Squares. We were able to find NVX 90mil for as low as $2.50 per square foot when buying an 80 sq foot bulk pack. Remember, ResoNix reduces the test panel’s resonance by 17db. NVX 90mil reduced the panel’s resonance by 11.5db. Based on this, we can calculate that ResoNix is 3.6x as effective as NVX. This means you would need to, in theory, apply 3.6x as much NVX 90mil to the test panel to get the same reduction as a given piece of ResoNix CLD Squares. Taking that 3.6x multiplier to their $2.50 per square foot price, we can calculate its price to performance vs. ResoNix would be $9, vs. ResoNix $8.20. We finally have something close, but when using this product, you would then have to go through the additional work of applying 3.6x as much product vs. ResoNix CLD Squares to get the same performance. Close, but no cigar.

Next, we have Roadstage Audio, which is a “3-in-1” product. Butyl, foil, and foam all in one package. Lets see how effective it is at reducing panel resonance. As you can see on the graph, the resonance reduced from 106.5dB, to 98dB. An 8.5dB reduction in resonance. ResoNix 17dB reduction allows us to calculate that ResoNix is 7.1x as effective per given amount compared to Roadstage Audio. I cannot find a website for Roadstage, let alone pricing, so we have no way to calculate the price to performance ratio. That said, I have a hard time believing that it’s cheap enough (especially considering it’s a 3-in-1 product) to be anywhere in the ballpark of the value of ResoNix CLD Squares.

Next up, we have Sonic Barrier MX-4. Another 3-in-1 product similar to Roadstage. Frankly, there are a LOT of products like this nowadays. Almost all of them are made by one manufacturer overseas with a different logo applied for each company. Roadstage says theirs is from another factory, which I believe. But Sonic Barrier is one of the ones in the “same as the rest” group. The only difference you can really get is butyl and foam thickness. Sonic Barrier is the thinnest we have seen from this manufacturer. So, getting into the test results. Sonic Barrier MX-4 reduced the panel resonance from 106.5dB to 99.5dB, a 7dB reduction. Considering ResoNix had a 17dB reduction, we can calculate that ResoNix is exactly 10x as effective per given area covered than Sonic Barrier MX-4. We were able to find Sonic Barrier MX-4 for $2.85 per square foot. The price to performance value comes out to $28.50 vs. ResoNix at $8.20 per square foot. While the initial cost is attractive, this is not a good value.

Up next is Second Skin Damplifier Pro. This is regarded as one of the best CLD’s on the market. Let’s see what the data says. According to the graph, we have a resonance peak reduced from 106.5dB to 95.5dB, an 11dB reduction. This is among the better products, but definitely not the best. Let’s compare to ResoNix to see what value you get. ResoNix CLD Squares reduce 17dB of the test panel’s resonance, a 6dB difference vs. the Second Skin Damplifier Pro. This 6dB difference equates to ResoNix being 4x as effective per given amount than the Second Skin Damplifier Pro. You can get Second Skin Damplifier Pro for as low as $6.16 per square foot if you order their 120sq foot bulk pack. Highly unlikely that anyone is ordering that much, but let’s use it for the sake of argument. Second Skin Damplifier Pro price to performance ratio comes out to $24.64 vs. ResoNix $8.20. And again, you would still need to go through the work of applying, in theory, 4x the amount to get the same result. This is not a good value.

Below, you can see all the results stacked onto the graph with the reference “before application” measurement.

So here are some bar graphs to represent resonance control, a graph to represent the overall value, and a graph to represent the amount of square footage needed of a given product to match the performance of 1 square foot of ResoNix CLD Squares.