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Old 05-11-10, 10:38 AM   #11
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Re: Constraint Layer Damping


Quote:
lsiberian wrote: View Post
20 bucks for roofing material is a far cry from the cost of the amps and crossovers.
I'd use Dynamat or a comparable product. It won't smell bad like that asphalt based roofing stuff does.

The treatment should work best if you place it between two layers of equal thickness. That puts the damping material right at the location of max shear in the panel, maximizing effectiveness.


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Old 05-11-10, 10:44 AM   #12
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Re: Constraint Layer Damping


It's probably not on the interwebs anymore, but back in the 90's when I first got into subwoofer building, there was a guy who would make his own composite panels and then build the box.

Basically it was 3/4" MDF -- roofing felt -- 3/4" MDF sandwich. He would then miter the edges or carefully design a box in a box so that the felt layer was never short circuited by contact with an outer layer of MDF. It was a lot of extra work, but he swore by the damping effects. Not sure what adhesive he used, it's been a while.

I was researching NHT1259 sub designs at the time, might have been the old Bass-list.


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Old 05-11-10, 10:44 AM   #13
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Re: Constraint Layer Damping


I've also thought about using honeycomb sandwich panel construction but the cost seemed to outweigh the benefits. Maybe a foam core sandwich panel could be constructed DIY and really help reduce the weight of the cabinets while maintaining excellent panel stiffness. The foam core may act as a damping material in the process.


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Old 05-11-10, 02:08 PM   #14

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I started this thread.
Re: Constraint Layer Damping


Quote:
vann_d wrote: View Post
I'd use Dynamat or a comparable product. It won't smell bad like that asphalt based roofing stuff does.

The treatment should work best if you place it between two layers of equal thickness. That puts the damping material right at the location of max shear in the panel, maximizing effectiveness.
Peel-n-seal is what one of my friends uses. The exterior structure will be 3/4" plywood and quarter round on the edges to help with baffle step and make finishing quick work. I'm quite sure this is overkill, but that's the point of this build.

Constraint Layer Damping, A bracing matrix and thick Rockwool treatment is more than my current speakers have.


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Old 05-16-10, 12:14 AM   #15
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Re: Constraint Layer Damping


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http://www.silcom.com/~aludwig/Louds...ration_damping has a very good article on the subject and suggests using 30 lb. roofing felt.

I'm wondering if any of you have experiences with constraint layer damping in loudspeakers.

The gentlemen measured a 20db decrease in panel vibrations which I found impressive.
I remember the old Ludwig build, but hadn't read it in ages. My first thought reading your initial post was 'what the is 30lb roofing felt?'. Turns out we have a similar product here called Malthoid dampcourse which is about $A13 for a 100mm wide 20m roll so I think I'll give some a try in the speakers on the interior walls. Not sure what to glue it to the walls with though. I've emailed and enquiry over the w/e and hope I'll get a response.

Vann's post 2 is my understanding of CLD (better expressed too).

Quote:
vann_d wrote: View Post
I've also thought about using honeycomb sandwich panel construction but the cost seemed to outweigh the benefits. Maybe a foam core sandwich panel could be constructed DIY and really help reduce the weight of the cabinets while maintaining excellent panel stiffness. The foam core may act as a damping material in the process.
Many years ago, about the time of the SL600 Celestions, a friend built some speakers and subs with a Styrofoam core and Laminex skins. It was very light and stiff and seemed to work well but we had no way of measuring back then. Each skin was added over the 50mm thick styro and left to dry. Panels were cut and mitred and glued to each other to form the enclosure. The baffles had marine ply behind the drivers to give extra support.
The speakers were huge, a big 4 box sort-of line array a la Infinity IRS.


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Old 05-16-10, 07:11 AM   #16
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Re: Constraint Layer Damping


Quote:
I'm wondering if any of you have experiences with constraint layer damping in loudspeakers.
Lots of DIY stuff.
Found the roof felt too cumbersome and difficult to work with.
I also tried the layer technique in SpeakerBuilder 3/89 of layering veneer plywood with drywall sandwiched in between. Again cumbersome and difficult.
Another article in SB 5/96 ( Hajo Prodan "The Opposite Moduli(OM) Speaker Cabinet" ) lead me to OM compounds and try laminating layers of plywood with silicone RTV.
While messy to work with it created panels that were much more inert than layered ply.
On my later subs I did not want to resort to a layered "brute force" technique, so I made an acoustic mud compound to grout on the inside of the sub panels.


Syd


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Old 05-20-10, 03:14 PM   #17
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Re: Constraint Layer Damping


Yoo All

Currently building curved speakers using 1/6" sheets of PVC bonded with Neoprene to a thickness of 3/4"
Best enclosures I have build in 30 years of building
Cheers
Sunny


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