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constrained layer damping with MDF and Ply
constrained layer damping with MDF and Ply
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Old 17th October 2009, 07:05 AM   #21
pheonix358 is offline pheonix358  Australia
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One I tried when doing R&D worked well. Two layers of HD3 bonded with 3mm sheet rubber. The rubber is usually used to water proof decks, concrete roofs etc. I used a contact cement to glue them together. The vibration energy didn't get through the rubber. Bad side was trying to fit the panels together. Only way to easily do that was to use corner sinks. These are heavy corners designed to stop any energy from going from panel to panel. Worked well but the corner had a tendancy to fix the two sides at the edges.

The attached pic is from the initial tests of using corner sinks just to explain a little better. Corner material was Jarrah, a very dense timber.
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Old 17th October 2009, 10:14 PM   #22
rcw is offline rcw  Australia
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An interesting paper on the subject of constrained layer damping is here..


This clearly shows that the energy dissipated by the constrained layer is proportional to the area enclosed by the hysteresis curve, and indicates how much typical polymers have to be strained to get them into the hysteresis region, much more than the walls of any speaker box I would want.
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Old 18th October 2009, 03:20 AM   #23
critofur is offline critofur  United States
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Originally Posted by bmwman91 View Post
I think that the biggest challenge will be to get the bonding coverage you want. How viscous/thick is the "green goo" you mention? I think that you will need to be able to apply high pressure evenly across the entire surface of the boards you want to mate.

For the Green Glue to be effective, you want there to be some space between the two panels, only attach them at the edges/corners.

Ideally, you would build two seperate shells seperated by lines of green glue spaced every couple of inches - the two seperate walls of the enclosures would not be firmly attached except at the corners.

The inner enclosure would be well braced.
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Old 18th October 2009, 03:41 AM   #24
Pano is offline Pano  United States
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constrained layer damping with MDF and Ply
Originally Posted by MJL21193 View Post
I used clear silicone to bond the layers together:
Any particular type or brand you like? Do you buy the tubes that go in a caulking gun?
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Old 18th October 2009, 04:13 AM   #25
56oval is offline 56oval  Australia
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I was talking with the supplier of GreenGlue in Oz ,they made an internal cabinet then covered it with green glue then made an external cabinet to encapsulate the internal cabinet .The gap between the 2 layers was not greater than 0.5mm and both board's were the same thickness and material for CLD to work .

SikaFlex and LocTite make a similar product but minimum thickness needs to be 2mm .

For my own cab's I'm using 5086 alloy and ply .The alloy baffle's are light weight and very stiff no flex .

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Old 18th October 2009, 04:41 AM   #26
MJL21193 is offline MJL21193  Canada
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Originally Posted by panomaniac View Post
Any particular type or brand you like? Do you buy the tubes that go in a caulking gun?
I use GE Silicone 1 which seems to set faster and has better adhesion than Silicone II. They come in a tube for a regular caulking gun.

It would be interesting to do a comparison between a CLD type panel and a one piece panel (but thicker). Using an accelerometer, measure the vibration from the inside of the panel and the outside on both panels and see if there is a difference.
According to rcw, the thicker, one piece panel with transmit less energy to the outside due to it's superior stiffness.
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Old 18th October 2009, 04:52 AM   #27
Pano is offline Pano  United States
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constrained layer damping with MDF and Ply
Well I guess the silicon and Green Glue have the advantages of being faster, lighter, easier and maybe cheaper than sand filled. Sand filled does work great, tho... (Royal P.I.T.A)
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Old 18th October 2009, 07:08 AM   #28
TerryO is offline TerryO  United States
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Speakerlab, here in Seattle, used to make their cabinets using a glued up laminate consisting of a 1/2 inch particle board (not MDF) inner layer, glued to a 3/4 inch plywood outer layer. They used mitered edges for appearance and to increase the area of the gluing surface.

Heavy, but very effective, as the dissimilar materials and thickness would serve to cancel different frequency ranges and modes.

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Old 18th October 2009, 07:14 AM   #29
rdf is offline rdf  Canada
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I'll bet one of their '70s catalogs is floating around my parent's house. Big into horns as I recall.
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Old 20th October 2009, 10:28 PM   #30
Antripodean is offline Antripodean  Australia
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Thanks everyone for all the input. FWIW I see the simple lamination of chipboard and ply as damping and will look to something more in the line of CL damping as has been suggested in many of posts with various innovative solutions. Largest panels are 750x600mm so I will need to see if this really justifies the design approach or whether a nearly as good result would be achieved from focusing on the bracing.
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