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Discussion Starter #1
For whatever reason, when I started my sound deadening I was not going to use MLV. I have since decided to use it, at least in the floors and back wall. Perhaps doors as well when I get to them.

Just checking my understanding and a couple questions.

The idea is to have a barrier, meaning sealed to keep noise out.

How do I treat the areas around studs coming up through the floor or bolts going into the floor.

My base layer is BXT2 followed by ensolite. On top of that will be the MLV.

Do I glue it to the foam or as long as it will stay in place, that is all that matters?

My amp rack is glued to the back wall. I am thinking CCF between the back wall and the amp rack where there is no glue, then closed cell foam over the plywood rack then MLV over the whole thing. Right thinking?
 

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You don't need MLV to create a quite car. CCF will do the job just fine and well.
 

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You don't need MLV to create a quite car. CCF will do the job just fine and well.
You don't need MLV specifically, but you do need a barrier to keep noise out of the passenger compartment. CCF is a mechanical not an acoustical material - it keeps one thing from making contact with another. It isn't dense enough to block sound effectively and it's a poor absorber of sound for the same reason it doesn't absorb moisture. Even if it were an effective absorber, it wouldn't help much in a thinner layer since frequencies absorber are directly related to the absorber's thickness.

For whatever reason, when I started my sound deadening I was not going to use MLV. I have since decided to use it, at least in the floors and back wall. Perhaps doors as well when I get to them.

Just checking my understanding and a couple questions.

The idea is to have a barrier, meaning sealed to keep noise out.
Yes.

How do I treat the areas around studs coming up through the floor or bolts going into the floor.
You make the holes in the barrier as small as you can. A hole with a heavy steel bolt passing through it really isn't an open hole - the bolt counts :)

My base layer is BXT2 followed by ensolite. On top of that will be the MLV.

Do I glue it to the foam or as long as it will stay in place, that is all that matters?
As a general rule, you want to make as few permanent changes to the vehicle you can. Gluing stuff to the sheet metal seems to guarantee that you'll need to get under it in the future. ;)

The only adhesive you'll need on the floor will be used to seal seams in the barrier layer. Carpet, seats, trim and gravity will hold the CCF and MLV in place.

My amp rack is glued to the back wall. I am thinking CCF between the back wall and the amp rack where there is no glue, then closed cell foam over the plywood rack then MLV over the whole thing. Right thinking?
Probably. The guiding principle of the design should be to create as close to a complete envelope, below the glass line, as you can. Depending on what the amp rack is made of, it may be creating a barrier itself. The ideal barrier is limp and dense. Depending on how much mass/area the amp rack creates, adding a barrier layer over it may or may not improve things.
 

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Yeah, ^^ what he said ^^. :)

You can see how I did mine in my build thread HERE. I've got quite a few pictures to look at. The deadening part starts around post #65.
 

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What "lb" or STC is the MLV most of your are using? Is .5lb (STC 20) adequate? This is about 1/16" of an inch thick. I'm assuming this is put between the door card and the metal and therefore can't be very deep. Also assuming no CCF is needed underneath it.
 

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1/8" 1lb. Per sq ft.
 

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1 lb is what I seem to see used most around here. I just finished "deadening" my car and concentrated more on the ccf and mlv than I did with the CLD tiles. I was fortunate in that my car comes fairly deadened from the factory (lexus). Rudeboy and Don both seem to really know their stuff and are a great resource to use in your research. check their websites, contact them via pm or email, and purchase correctly the one time. Is amazes me how much the science of quieting a car down has come since my inception to it in the mid 80's. Best of luck.
 

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What "lb" or STC is the MLV most of your are using? Is .5lb (STC 20) adequate? This is about 1/16" of an inch thick. I'm assuming this is put between the door card and the metal and therefore can't be very deep. Also assuming no CCF is needed underneath it.
Between the door card and inner skin is the ideal placement since it puts noise entering the door through the front, rear, top and bottom behind the barrier. It will also acoustically reinforce the plane between a door mounted speaker's front and rear waves.

Outer skin placement will still do a decent job with noise and also makes it harder to hear door mounted speakers from outside the vehicle. Doing both is great, but is probably overkill for most applications.

You really want to decouple the barrier from the sheet metal if at all possible. It generally is, with care. My preference is to get as close to a full layer of CCF as I can between the MLV and inner skin. I'll then add as much CCF as will fit to the side of the MLV facing the trim panel, enough to compress very slightly when the trim panel is reinstalled. If there absolutely isn't space, I'll skip the layer between the MLV and inner skin and make sure there is enough on the other side to press the MLV tightly against the inner skin. If there's no room at all, I'll go to the outer skin.


Rudeboy and Don both seem to really know their stuff and are a great resource to use in your research. check their websites, contact them via pm or email, and purchase correctly the one time.
Thank you, but Don = Rudeboy - you're freaking me out a little ;)
 

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What "lb" or STC is the MLV most of your are using? Is .5lb (STC 20) adequate? This is about 1/16" of an inch thick. I'm assuming this is put between the door card and the metal and therefore can't be very deep. Also assuming no CCF is needed underneath it.
Sorry, forgot to address the first point. Each time you double the mass of a barrier, you get an extra 6 dB attenuation. It doesn't work out exactly that way in practice, largely because you need to consider the mass of what you are starting with. Still, the more mass you add, the better off you are going to be. There isn't a huge difference in difficulty between 1/8" and 1/16". 2 lb/ft² is available, but is 1/4" thick and considerably less flexible.
 

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I used CCF for my car and was HUGE difference. You can get similar results with CCF compared to MLV. Not only that, you don't have over 100 pounds of deaden-er.
 

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I used CCF for my car and was HUGE difference. You can get similar results with CCF compared to MLV. Not only that, you don't have over 100 pounds of deaden-er.
You're saying you used CCF and nothing else? You're also saying you've used MLV and CCF in the same vehicle in a previous install, pulled it out and replaced it with just CCF and got "similar results"?
 

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Thanks for the replies. I have ccf (about 1/8" thick) from a previous project. Is the thickness of this more or less important than the MLV? I understand the CCF is for isolation, the MLV is for deadening and the butyle/AL layer and expanding foam in crevices is for reducing the resonant frequency (and stiffening) as I understand it. My thought was to have a layer of MLV, then CCF then another layer (of 1/2lb) MLV. In areas where this was too thick there would just be a layer of MLV. On doors the CCF would be trimed back from the edges and where the card is attached through to the metal to allow a thicker layer where it fits.
 

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Thanks for the replies. I have ccf (about 1/8" thick) from a previous project. Is the thickness of this more or less important than the MLV? I understand the CCF is for isolation, the MLV is for deadening and the butyle/AL layer and expanding foam in crevices is for reducing the resonant frequency (and stiffening) as I understand it. My thought was to have a layer of MLV, then CCF then another layer (of 1/2lb) MLV. In areas where this was too thick there would just be a layer of MLV. On doors the CCF would be trimed back from the edges and where the card is attached through to the metal to allow a thicker layer where it fits.
CCF is a mechanical material - it has almost no useful acoustical value. As such, all you're doing is separating the MLV from resonant surfaces. Air would work if we could maintain the gap, and that's what CCF does. Since we're not worried about CCF defying the laws of nature and absorbing sound, the only issue is whether or not the CCF will maintain that gap in use. In my experience, 1/8" is enough to maintain that gap everywhere except the foot wells where it undergoes constant compressions. I use 1/4" (or 2 layers of 1/8" there). It's also important not to feel vibration through your feet and legs, so the foot wells need to be well isolated.

I'd expect the expanding foam to reduce the amplitude of the resonance and raise its frequency. Stiffing raises a panel resonant frequency. Two things to consider. Filling cavities with expanding foam is all but irreversible. I try to remember to ask myself if the permanent changes I make to the vehicle are worth the potential benefit. If the area you treat are subject to twisting or other gross movements, you can get squeaking.
 

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Discussion Starter #15
Follow up question on this.

My MLV is one sheet on the back, and then it takes 3 pieces to cover the floor. A truck floor is much easier than a car floor, just bigger.

Anyway, There is a piece of MLV that runs down each side of the floor and then a piece over the center hump that completes the floor. To make it easier to remove if I ever have to I would like to overlap the seams and tape instead of glue. That way I could pull the floor out in 3 sections

Will that present a significant issue with a 1"+ overlap with taped seams? I'll glue if it is a lot better for this specific instance.
 

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Follow up question on this.

My MLV is one sheet on the back, and then it takes 3 pieces to cover the floor. A truck floor is much easier than a car floor, just bigger.

Anyway, There is a piece of MLV that runs down each side of the floor and then a piece over the center hump that completes the floor. To make it easier to remove if I ever have to I would like to overlap the seams and tape instead of glue. That way I could pull the floor out in 3 sections

Will that present a significant issue with a 1"+ overlap with taped seams? I'll glue if it is a lot better for this specific instance.
No performance problem. May not even have to tape it if you can be sure the seams will stay overlapped. If you do have to tape you'll need one with a vinyl compatible adhesive. It's been a long time since I tried that but I think you want an acrylic adhesive.

All for the removable approach.
 

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As long as you get the carpet and any other pannels and/or consoles back in your good.
Just be sure not to leave any kind of gap between the two pieces or noise will most def come through said gap.
Defeating the whole purpose behind what your doing.
Edit: If you feel like the tape your using has enough stregnth to hold the pieces the together for however long you need it to then no there will be no ill effects.
 

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Discussion Starter #18
The tape is designed for it. I bought it when I bought the mlv. It will hold enough to get the carpet in.

I sure hope everything goes back in. Tomorrow I should be able to get the pad and carpet in, the amps and distribution blocks and the back seat.
 
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