# Report: is closed cell foam the right material to decouple mass loaded vinyl?



## Justin Zazzi (May 28, 2012)

Back in the summer of 2017 I wanted to test a common rule of thumb: mass loaded vinyl should always be decoupled from nearby surfaces, and closed cell foam is the right material to do it.

Many of you kindly donated materials for this experiment and I am very, very thankful for it. I am thrilled to finally finish and post the results. This took a very long time to write because I did not have a solid method to interpret the results until just recently when we covered the transmissibility ratio in an acoustics class I'm taking. I apologize for the delay, but I hope the wait is worthwhile.

the report is at my dropbox here --> MLV decoupling report v1.3


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## SkizeR (Apr 19, 2011)

*proceeds to order 1 ton of pillow stuffing to market as my own decoupler* 

Glad you got around to this. Thanks.


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## seafish (Aug 1, 2012)

awesome to see this written up!! Thanks!!!


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## 04quadcab (Dec 31, 2017)

Nice work.


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## fish (Jun 30, 2007)

Thank you sir, for taking the time to do the research, & saving me some time & money!


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## Holmz (Jul 12, 2017)

That is quality work.


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## karmajack (May 9, 2017)

Question. So what if the MLV can't hang free. Is it going to introduce noise? If MLV is used, without adding a dedicated decoupling material, and it is decoupled by trim panels and sheet metal, is that worse than no MLV at all?


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## brainbot1 (Feb 19, 2016)

Thank you for this. I use 1/8" neoprene stuck to both sides with contact adhesive but now this has me thinking....


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## kanadian-kaos (Sep 12, 2010)

Whoa. Good read. Thanks for putting in the effort.


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## captainobvious (Mar 11, 2006)

Is there actually a claim that using CCF between the MLV and door is done to enhance the effectiveness of the MLV specifically to block noise? I've never read that. Are there manufacturers/sellers claiming that?
I had always thought the intention of CCF between the door and MLV was to decouple to _*prevent any vibration/resonance of the MLV against the door panel*_...Which makes sense.


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## K-pop sucks (May 28, 2018)

From my research you need to start with a CLD tile with only 25% coverage( 2mm butenyl and 4mm aluminum gave the best measurements). Add a Closed cell foam as thick as you can find and place a mlv piece on top. Then apply 1" + inches of open cell foam on top. Each layer has an air gap. 

Interior panel: CLD tiles applied to with 25% coverage, 3m thinsulate 600L as the final noise barrier.


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## YeahWhatever (Dec 12, 2018)

WOW, great report sir. Thanks for your time. Nice to see the heat wave pro I used with my MLV tested good. Shocked to see how poorly most of the foams worked for decoupling.


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## SkizeR (Apr 19, 2011)

captainobvious said:


> Is there actually a claim that using CCF between the MLV and door is done to enhance the effectiveness of the MLV specifically to block noise? I've never read that. Are there manufacturers/sellers claiming that?
> I had always thought the intention of CCF between the door and MLV was to decouple to _*prevent any vibration/resonance of the MLV against the door panel*_...Which makes sense.


ive seen claims of not decoupling causing the vibration from the car to just transfer to the mlv and cause it to not be very effective. dont remember if it is right from the companies, or some random diyma claim. I can see why it would be the case though.


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## beak81champ (Oct 2, 2015)

So, I don’t see what any recommendation might be. Is there a certain thickness of polyester open cell foam (pillow stuffing) that could be used to decouple, assuming we would only use in dry areas, such as under interior carpet, inside rear quarter panels, etc. How thick would this need to be before the MLV crushes it and renders it ineffective? Does 1lb sq ft vs. 2lbs sq ft MLV matter? Should we still utilize Richard Vedvicks method in the door and scrap the CCF MLV method? I obviously have more questions than answers, lol.


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## Holmz (Jul 12, 2017)

I guess the main case that was left untested then was:
N) MLV connected using Velcro?


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## Justin Zazzi (May 28, 2012)

karmajack said:


> Question. So what if the MLV can't hang free. Is it going to introduce noise? If MLV is used, without adding a dedicated decoupling material, and it is decoupled by trim panels and sheet metal, is that worse than no MLV at all?


A mass loaded barrier will reduce noise transferring from one side to the other. It could possibly introduce noise by rubbing/buzzing against a nearby surface if the conditions are just right, but generally not.



captainobvious said:


> Is there actually a claim that using CCF between the MLV and door is done to enhance the effectiveness of the MLV specifically to block noise? I've never read that. Are there manufacturers/sellers claiming that?
> I had always thought the intention of CCF between the door and MLV was to decouple to _*prevent any vibration/resonance of the MLV against the door panel*_...Which makes sense.


The two ideas you have are the same thing. Vibration of the mass loaded vinyl is transferring noise, no matter what causes it to vibrate. Manufacturers may or may not be claiming the decoupling works this way or that ... but manufacturers are catering to the idea by making vinyl pre-glued to foam or lead sheeting pre-glued between layers of foam etc. Decoupling using closed cell foam is also ingrained in the culture here for example see the next comment below \/



K-pop sucks said:


> From my research you need to ... Add a Closed cell foam as thick as you can find and place a mlv piece on top...


My research shows otherwise. I encourage you to run an experiment with your approach and let us know how it goes!



beak81champ said:


> So, I don’t see what any recommendation might be. Is there a certain thickness of polyester open cell foam (pillow stuffing) that could be used to decouple, assuming we would only use in dry areas, such as under interior carpet, inside rear quarter panels, etc. How thick would this need to be before the MLV crushes it and renders it ineffective? Does 1lb sq ft vs. 2lbs sq ft MLV matter? Should we still utilize Richard Vedvicks method in the door and scrap the CCF MLV method? I obviously have more questions than answers, lol.


If you squish a material to half it's original thickness, it will become twice as stiff (or more). If you use a vinyl that is twice as heavy, it can compensate for a spring that is twice as stiff. I did not investigate the ideal ratios to use because I consider it to be a narrow niche case and impractical for nearly everyone.

I believe the method of stuffing the door with absorbent material has some value and I did this in my build log before I learned of Richard's post. How much difference it makes, I'm unsure.



Holmz said:


> I guess the main case that was left untested then was:
> N) MLV connected using Velcro?


Velcro itself has almost no spring-like properties since it is designed to be fairly rigid, so it would not help to decouple the vinyl if used with 100% coverage. However, I think you're suggesting use velcro to hang it on the edges and leave the rest of the vinyl floating which is the recommendation I tried to make in the conclusion. If the vibration along the edge of the vinyl is "far" away from the middle of the vinyl where it is floating, the vibration isolation is excellent.


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## FordEscape (Nov 23, 2014)

Enlightening indeed, thanks for the effort.


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## beak81champ (Oct 2, 2015)

Thank you for this project, and especially answering our questions using your findings! You guys that do these experiments and objective comparisons make it much easier for the rest of us to chose equipment, materials, ideas to clone, and save a bunch of money. I, for one, certainly appreciate all of you knowledgeable guys helping out the rest of us!!!


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## ckirocz28 (Nov 29, 2017)

Thanks for your work and thanks to those that donated materials to support your work! It's great to see some scientific answers to our burning questions in this hobby.


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## Justin Zazzi (May 28, 2012)

ckirocz28 said:


> Thanks for your work and thanks to those that donated materials to support your work! It's great to see some scientific answers to our burning questions in this hobby.


Yes indeed, a huge thank you to everyone who donated materials for this experiment. We all sincerely appreciate the kindness!


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## GreatLaBroski (Jan 20, 2018)

SkizeR said:


> *proceeds to order 1 ton of pillow stuffing to market as my own decoupler*
> 
> Glad you got around to this. Thanks.


I wonder how well this would work: take tyvec sheets, cut to match your door card, sew shut on the edges, then fill with synthetic pillow stuffing. Place in between MLV and door.


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## GreatLaBroski (Jan 20, 2018)

Justin Zazzi said:


> Yes indeed, a huge thank you to everyone who donated materials for this experiment. We all sincerely appreciate the kindness!


Thanks for taking the time to do this!


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## K-pop sucks (May 28, 2018)

I made a mistake regarding closed cell foam thickness, greater than 3/8's gives marginal returns. The only benefit of open cell foam is when it's thickness can be 2" or more in thickness. That's why open cell foam isn't recommended.


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## preston (Dec 10, 2007)

Thanks Justin. I always have had my doubts about needing to add the CCF layer. In most cases the MLV is pushed down by the weight of the carpet or tnesion of the trim pieces. Yes its possible MLV could be hung in a way to pick up some vibration, but I would think the vibration of that metal would have to be of significant amplitude to excite the MLV. In 90% of my MLV installs I don't believe that is happening. I've certainly never found a resonance related to my MLV installs . I don't really mind a little extra cost for the CCF, I just minded the extra labor of attaching it. I will no longer be using it. Especially since my product of choice was the RAAM Ensolite which tested very poorly !


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## Theslaking (Oct 8, 2013)

Products like Ensolite are a good idea. Justin is saying it does not stop the transfer of vibration to the MLV but it certainly stops a panel from buzzing or a clip from slapping against the MLV. I personally will still use it as that was my intention to begin with. I never interpreted the idea in a way that metal transferred vibration to mlv which in turn vibrated causing resonance. I actually always thought that it was to stop stuff from vibrating against each other.


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## Holmz (Jul 12, 2017)

Justin Zazzi said:


> ...
> 
> Velcro itself has almost no spring-like properties since it is designed to be fairly rigid, so it would not help to decouple the vinyl if used with 100% coverage. However, I think you're suggesting use velcro to hang it on the edges and leave the rest of the vinyl floating which is the recommendation I tried to make in the conclusion. If the vibration along the edge of the vinyl is "far" away from the middle of the vinyl where it is floating, the vibration isolation is excellent.


We should know the stiffness without numbers, but it probably is non linear and very stiff with no movement.

Do I conclude that I want it to hang, or do I still want a layer of something else under it?
And do I still want neoprene layer for the Velcro to attach to?


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## Justin Zazzi (May 28, 2012)

I was trying to recommend letting the vinyl float and not be firmly attached where possible, such as the vertical surfaces on the inside of door trim panels.

Beyond that, it would be ironic if I tried to recommend a certain rule of thumb since the conclusion of this experiment was to disprove a certain rule of thumb. I do not yet have anything better to replace it with other than be practical with both your time and money in terms of what you enjoy about this hobby.


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## Jscoyne2 (Oct 29, 2014)

I figure this is a good place to ask this considering it's a similar subject.

Whats your thoughts on FG enclosures like spare tire sub boxes where the box hugs the exact dimensions of the vehicle? In regards to resonance and vibration transfer to the body. Would putting down CCF before laying the Fg be useful or no? 


Sent from my XT1710-02 using Tapatalk


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## JCsAudio (Jun 16, 2014)

Jscoyne2 said:


> I figure this is a good place to ask this considering it's a similar subject.
> 
> Whats your thoughts on FG enclosures like spare tire sub boxes where the box hugs the exact dimensions of the vehicle? In regards to resonance and vibration transfer to the body. Would putting down CCF before laying the Fg be useful or no?
> 
> ...


Hey Jscoyne2,

I havent done a fiberglass enclosure but I will say that coupling the sub box to the vehicle helps with the sensation of bass throughout the vehicle, especially in the lower octaves because it transfers vibrations to the structure which you will feel. Now obviously you don’t want rattles so that is where using something like CCF along with typical sound deadening methods might help. 

I’m no expert but have experimented with this and in my opinion it does make a difference. I will let the fabrication experts chime in on the CCF specifically though.


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## Justin Zazzi (May 28, 2012)

I think it's all about goals. If you enjoy feeling the bass then by all means clamp that enclosure to the car and have fun. Also, the more you bolt it down the less it can become a projectile if you're ever in a crash.

If you want to float it and decouple it, you have the same challenge as mass loaded vinyl. You should find a decoupling material that is soft enough to isolate it, relative to how heavy it is. Most materials used in car audio do not have published stiffness values so the only advice I could offer is grab something like a set of rubber anti-vibration mounts from an industrial supply company, something used to isolate small power generators or small machinery. Those are usually specified with stiffness or with how much weight they are designed to decouple and at what frequency etc..

I doubt any of that would work for a custom molded enclosure like a JL Audio Stealthbox because they are designed to be fitted exactly one way and you'll have a crazy challenge trying to do something different. Even if you could fit something squishy between the box and the car, it still gets clamped to the car with bolts so that defeats the purpose of trying to float it.

A much much easier thing would be to mount two speakers opposing so they cancel the vibrations of eachother and then you don't need to worry about anything else.

See the Sonos home subwoofer for example:


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## SkizeR (Apr 19, 2011)

I do my best to totally decouple enclosures from the car as much as possible. The last thing you want to do is transfer the vibration from the enclosure to the rest of the car. 

Sent from my SM-G950U1 using Tapatalk


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## dgage (Oct 1, 2013)

For large home theater subwoofers I use 3 layers of 1/8” rubber from Tractor Supply (roll) interspersed with a pair of 1/2” plywood sheets. For a car I’d probably try thinner rubber like maybe multiple layers of the rubber used for drawer liners. And you can also get rolls of cork at a hardware or office supply. 

And if you’re trying to do a complex shape, you might want to look into cans of Plastidip or Flexseal that can be applied with a brush, which would give you a rubberized coating. Maybe you could use strips of cork above that and even apply them while the rubber is wet so the cork is adhered, which would provide some spacing/isolation for your enclosure. But as soon as you bolt the enclosure to the car, unless you use an isolation mount, you’re going to transfer vibrations into the cars structure.


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## sazabi2001 (Feb 12, 2019)

Hummm, find this just before I re-do all my car interior. Does this means I'd better use 3M Thinsulate rather than CCF + MLV?


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## JCsAudio (Jun 16, 2014)

Feeling the bass as well as hearing it is an important part of the equation. High end theaters use bass shakers for this very reason because the sensation of bass is just as important as hearing it. Sound traveling through air also loses energy much faster than it does traveling through a solid. I deal with that when we design buildings and don’t want sound to travel through walls or floors. In those cases, decoupling the walls is more effective than adding mass or insulation to increase the STC ratings. I also renovated the Bose research and development building years ago and learned a lot. Those engineers do some amazing **** in that building. My crew was the first to construct a sound room for them that didn’t rattle in years. 

In car audio, the school of thought is “we don’t want rattles” and from an installers point of view I can understand this as you don’t want customers coming back complaining about a rattle in the door or similar. For me, the trick is to couple the subwoofer to the structure of the vehicle AND deaden all the rattles that it might produce. The above mentioned securing the box down to prevent that the box from becoming a skull crushing projectile in an accident is also important and obviously when you do this you’ve just coupled the box to the car. Build a fiberglass enclosure, even with foam between the car metal and sub box and guess what, you’ve just coupled the box to the frame of the car. I think you guys do it all the time and may not even know you are coupling the box to the car. It’s a balancing act between rattles and feeling the bass. Going with huge cone area and thousands of watts is another way to feel the bass too but that costs much more. :laugh:


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## Justin Zazzi (May 28, 2012)

sazabi2001 said:


> Hummm, find this just before I re-do all my car interior. Does this means I'd better use 3M Thinsulate rather than CCF + MLV?


Please re-read the last sentence of the conclusion.


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## reburns (Apr 1, 2019)

I'm a little confused by the testing & report... that the MLV samples were 1.5" square, and the wavelength of the sound frequency is long, on the order of feet. The MLV functions to deflect with the sound pressure, and by virtue of internal coulomb friction turn that displacement energy into heat and not just act as a fixed mass against an undamped CCF spring? Would we see much different results from a large coupon? I only have questions, not answers!


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## fftfk (Apr 29, 2019)

New project this weekend - angrily rip out all of the ensolite I painstakingly applied to my whole car!!!!

Great job on the research.


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## Bosanek (Apr 16, 2019)

If I might add a question to this debate:

If most of MLV sheet's surface is secured to a vertical panel (like a plastic trim card on a side door) using glue or plenty of velcro strips, I don't see a need to use any decoupler between the MLV and the trim card.
The only way for MLV to vibrate in that setup is if the entire trim card would vibrate with it, and that would take a lot of force to "excite".


Is this thinking correct?


By the way, has anyone used an automotive-grade glue (example: roof upholstery glue) instead of velcro strips to secure an MLV sheet to a vertical surface? Did it hold up in the long term?


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## LBaudio (Jan 9, 2009)

thanks for taking time to complete this research and educate uneducated


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## Justin Zazzi (May 28, 2012)

I have moved and so I welcome all new discussion in this thread below.

Report: is closed cell foam the right material to decouple mass loaded vinyl?


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## spwath (Apr 7, 2020)

Bosanek said:


> If I might add a question to this debate:
> 
> If most of MLV sheet's surface is secured to a vertical panel (like a plastic trim card on a side door) using glue or plenty of velcro strips, I don't see a need to use any decoupler between the MLV and the trim card.
> The only way for MLV to vibrate in that setup is if the entire trim card would vibrate with it, and that would take a lot of force to "excite".
> ...


In theory, decoupling isn't just to prevent rattle. It should help with sound isolation. 3 pieces of drywall will be much more effective at blocking noise is there is a space between them, rather than all put together.
The same thing applies here, you want a space in between the car door and the mlv (which is what the foam will do).
If you don't have a space, you just rely on the mass law curve, and it is much less effective at blocking noise.


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## opekone (Mar 24, 2020)

Very great work! I love the idea of mounting to the driver to create a simple and repeatable process where the harmonic resonance of the mounting surface is continuously variable.

I'm interested in the effect of the overall size of the MLV or the decoupling layer since they both gain their spring and dampening curves from the interaction of neighboring material. Replicating results with a much smaller piece, say, 5mm x 5mm, would go a long way to demonstrating the efficacy of this methodology.

In vivo, as it were, the speaker's output is significantly dampened and modified by the air and when it hits an object (like your inner door skin) it excites that object at it's natural harmonic resonance. While mounting directly to the speaker does provide a great view into the variability across difference resonant frequencies, I wonder if it's an accurate recreation of our use case. Here the only interaction we are seeing is that of the decoupler + MLV interacting with the harmonic resonance of the material. We don't assess it's ability to mitigate the airborne sound nor do we assess the combination of effects. This is particularly curious to me because in our application we typically use CLD rather than decoupled MLV to deal with harmonic resonance.

Is Jazzy even still here?


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## Theslaking (Oct 8, 2013)

opekone said:


> Is Jazzy even still here?


No



Justin Zazzi said:


> I have moved and so I welcome all new discussion in this thread below.
> 
> Report: is closed cell foam the right material to decouple mass loaded vinyl?


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## DirtyBumOak510 (May 31, 2020)

Justin Zazzi said:


> I have moved and so I welcome all new discussion in this thread below.
> 
> Report: is closed cell foam the right material to decouple mass loaded vinyl?


I like the scientific analysis. My only problem with the conclusions however is that they need to be put into perspective. The MLV on its own I think is a good solution. Having just installed (not reading the report first obviously) CLD, CCF and MLV, I have to say that there is NO WAY IN HELL that I could have used anything thicker than the 1/8" CCF that I used. I had a hard enough time getting my door panels back on to begin with. I think my takeaway from this is that you might as well just leave the CCF (or alternative) off completely.


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