Mass Loaded Vinyl

[ameuba10]

has anyone thought of using mass loaded vinyl as a sound barrier inside their box? ive followed car audio for years now and thought that this technique could be used in home audio as well.

 

[highfigh]

has anyone thought of using mass loaded vinyl as a sound barrier inside their box? ive followed car audio for years now and thought that this technique could be used in home audio as well.

You mean, something like DynaMat? A brace does the same thing- it breaks up the resonance mid- panel, and it's easier to install.

 

[ameuba10]

well in car audio we put dynamat on the door to kill resonance, then a closed cell foam over that, then the mass loaded vinyl as a sound barrier. mainly to keep out road noise and to keep musical sound inside.

 

[Alex2507]

Around here there has been talk of using Peel & Seal instead. I Googled it for a link but found this sort of interesting discussion that applies to automotive applications as well.

 

[Rickster71]

This looked interesting:

 

[highfigh]

well in car audio we put dynamat on the door to kill resonance, then a closed cell foam over that, then the mass loaded vinyl as a sound barrier. mainly to keep out road noise and to keep musical sound inside.

I know- I did car audio for over 20 years. The point of bracing a box is to keep it from resonating. The rest is overkill. DynaMat lowers the resonant frequency, bracing raises it to a place that it won't be a problem when it's caused by low frequencies. Also, unless the surface is right, Dynamat won't stick for long. Peel N Stick would probably work better- it's made for attaching to building materials and DynaMat is made for attaching to painted metal surfaces.

Give it a shot. If you're building your own and can actually test the results, build two boxes and add a second layer of MDF to the exterior, using wood glue and screws, staples or brad nails Then, measure the response and if possible, the cabinet's resonant frequency. If you have a lot of time and materials, try building the box with two layers of MDF and a layer of vinyl between them.

There's already a lot of info about this kind of thing- google is your friend.

 

[Loren42]

This looked interesting:

The stuff is made from recycled tires!

The road noise must be horrible!

 

[Loren42]

I know- I did car audio for over 20 years. The point of bracing a box is to keep it from resonating. The rest is overkill. DynaMat lowers the resonant frequency, bracing raises it to a place that it won't be a problem when it's caused by low frequencies. Also, unless the surface is right, Dynamat won't stick for long. Peel N Stick would probably work better- it's made for attaching to building materials and DynaMat is made for attaching to painted metal surfaces.

Give it a shot. If you're building your own and can actually test the results, build two boxes and add a second layer of MDF to the exterior, using wood glue and screws, staples or brad nails Then, measure the response and if possible, the cabinet's resonant frequency. If you have a lot of time and materials, try building the box with two layers of MDF and a layer of vinyl between them.

There's already a lot of info about this kind of thing- google is your friend.

Both approaches of stiffening and dampening do different things.

Rigidity does raise the resonance points of the panels and make the reduction of vibration easier to control.

The Dynamat (or its equivalent) works by absorption. Actually, it converts mechanical energy into heat. Bracing does not.

Imagine an infinitely well braced cabinet (cement is a good example). You have 100% of the rear wave energy now trapped or contained in the cabinet.

Actually, no. The rear wave will return to vibrate the cone of the driver or exit the port. This is where stuffing comes in. Like Dynamat it converts the mechanical acoustic energy into heat.

The point is, bracing alone is not sufficient. Adding a layer of Dynamat will help reduce the mechanical energy along with the use of stuffing.

As far as sticking inside the cabinet, I would not give Peel & Seal much better chance than Dynamat. I have a roll of Peel & Seal that has never been used and is a few years old. The glue has deteriorated so much so that it sticks to nothing.

The Peacemaker looks interesting, too. However, Vance Dickason points out that multiple layers of 30# roofing felt has been successfully used in the industry commercially for decades.

Roofing felt is loosely stapled to the inside walls with 3 to 5 layers. It is cheap and easy to deploy with little worry of adhesion issues.

That may be a simple and inexpensive alternative to mass loaded vinyl and the other products mentioned.

 

[lsiberian]

Both approaches of stiffening and dampening do different things.

Rigidity does raise the resonance points of the panels and make the reduction of vibration easier to control.

The Dynamat (or its equivalent) works by absorption. Actually, it converts mechanical energy into heat. Bracing does not.

Imagine an infinitely well braced cabinet (cement is a good example). You have 100% of the rear wave energy now trapped or contained in the cabinet.

Actually, no. The rear wave will return to vibrate the cone of the driver or exit the port. This is where stuffing comes in. Like Dynamat it converts the mechanical acoustic energy into heat.

The point is, bracing alone is not sufficient. Adding a layer of Dynamat will help reduce the mechanical energy along with the use of stuffing.

As far as sticking inside the cabinet, I would not give Peel & Seal much better chance than Dynamat. I have a roll of Peel & Seal that has never been used and is a few years old. The glue has deteriorated so much so that it sticks to nothing.

The Peacemaker looks interesting, too. However, Vance Dickason points out that multiple layers of 30# roofing felt has been successfully used in the industry commercially for decades.

Roofing felt is loosely stapled to the inside walls with 3 to 5 layers. It is cheap and easy to deploy with little worry of adhesion issues.

That may be a simple and inexpensive alternative to mass loaded vinyl and the other products mentioned.

Peel-n-seal is supposedly effective for constraint layer damping though I'd not suggest using this technique except on a long-term reference project. I suspect that in Dickason's project that the added mass has more to do with the improvement than the damping itself. I think it's overkill to use this method in nearly all loudspeaker designs. A well braced and internally damped box I think will provide good enough SQ that the need for a constraint layer damping system doesn't exist. This won't change my plans to use constraint layer damping on my reference project, but I don't plan to use it on any other projects. It makes construction far more complex than necessary IMO.

 

[highfigh]

Both approaches of stiffening and dampening do different things.

Rigidity does raise the resonance points of the panels and make the reduction of vibration easier to control.

The Dynamat (or its equivalent) works by absorption. Actually, it converts mechanical energy into heat. Bracing does not.

Imagine an infinitely well braced cabinet (cement is a good example). You have 100% of the rear wave energy now trapped or contained in the cabinet.

Actually, no. The rear wave will return to vibrate the cone of the driver or exit the port. This is where stuffing comes in. Like Dynamat it converts the mechanical acoustic energy into heat.

The point is, bracing alone is not sufficient. Adding a layer of Dynamat will help reduce the mechanical energy along with the use of stuffing.

As far as sticking inside the cabinet, I would not give Peel & Seal much better chance than Dynamat. I have a roll of Peel & Seal that has never been used and is a few years old. The glue has deteriorated so much so that it sticks to nothing.

The Peacemaker looks interesting, too. However, Vance Dickason points out that multiple layers of 30# roofing felt has been successfully used in the industry commercially for decades.

Roofing felt is loosely stapled to the inside walls with 3 to 5 layers. It is cheap and easy to deploy with little worry of adhesion issues.

That may be a simple and inexpensive alternative to mass loaded vinyl and the other products mentioned.

I can think of exactly zero speakers where I removed a woofer and saw roofing felt and I have repaired a lot of speakers. I'd like to see a list of the companies that have used it.

Vinyl damping material can be stapled in place, too- it doesn't need to be Peel N Stick and I was going to comment that the method of attachment makes a difference because the adhesive-backed stuff can and does fall off. I put some on my kitchen sink and as soon as the hot water hit it, the adhesive failed to hold it in place. This is actually a good example, too. Look at a stainless sink that has a small square of vinyl on it- it works well and covering the whole sink makes a difference but the noise is still not bad with just the small amount. Since the box is a different material, the affect will be different, though.

An infinitely stiff box will reflect the sound back to the cone and port but an inert panel may be better. Have you done anything with a thinner inner panel and a volume of sand behind it, to absorb the energy?

 

[Dennis Jaeger]

Late to respond to Highfigh but using roofing felt is (has been ) common in the UK for decades. users include the BBC (LS3/5A), KEF, Spendor. Harbeth, etc.