The "facts" are that at Snell we evaluated cabinet constructions for over a year and came up with two constructions that worked. One was a double baffle wit a layer of neopreen between 3/4" MDF layers (Snell K5, E5, XA90, XA75, XA55), the second was using a CLD sandwich with a Swedish sourced "noise killer yellow", formulated for high loss (XA Reference). Nuckle raps and accelerometer tests showed that the CLD approach was best and the internal material was critical.
I did try some floating issolation with foam intermediary layers. Although it can be made to work it is crucial that there are no rigid contact points between layers. This makes it hard to use in practice, such as in baffles.
The beauty of the constrained layer approach is tha screws through it seem to have no effect.
Get some Green Glue and glue a tile to a sample of wood. See if it holds or not. See if it dries out or not. While you are at it try contruction adhesive and see if it dampens or not.
Find your own facts.
David
I did try some floating issolation with foam intermediary layers. Although it can be made to work it is crucial that there are no rigid contact points between layers. This makes it hard to use in practice, such as in baffles.
The beauty of the constrained layer approach is tha screws through it seem to have no effect.
Get some Green Glue and glue a tile to a sample of wood. See if it holds or not. See if it dries out or not. While you are at it try contruction adhesive and see if it dampens or not.
Find your own facts.
David
These Sika urethanes should be perfect for the job....perfect adhesion to just about any surface, and nice lossy rubber like physical qualities.I've used Sikaflex a one-component polyurethane-based, non-sag elastomeric sealant. It's a very strong adhesive yet it maintains a slightly flexible property indefinitely. It'll easily glue the tiles to the exterior of your cabinet while simultaneously adding constrained layer damping. It doesn't cure to be hard like Liquid Nails. It's available in slow or fast cure.
Dan.
Using 2mm thick vinyl mat made by Con-Tact (Kittrich Corporation), Grip Premium Liner. Comes in 18"x48" rolls and available @HD
Thanks for the additional insight Dave.
I've written to Green Glue Company again for some advice on drying.
What about this idea: drill thru holes in a 2 inch grid in the plywood to allow drying air closer to access the GG layer. Normally this wouldn't work with traditional GG application method of squirting glue bead onto the wood with no spreading, but in the past I have troweled out a thin layer of GG with small notch trowel to improve surface coverage, which should increase damping. This would allow the GG and tile to seal up the air holes and speed drying. Only concern is that it might leak. No holes within 2 inches of the tile edge.
I've written to Green Glue Company again for some advice on drying.
What about this idea: drill thru holes in a 2 inch grid in the plywood to allow drying air closer to access the GG layer. Normally this wouldn't work with traditional GG application method of squirting glue bead onto the wood with no spreading, but in the past I have troweled out a thin layer of GG with small notch trowel to improve surface coverage, which should increase damping. This would allow the GG and tile to seal up the air holes and speed drying. Only concern is that it might leak. No holes within 2 inches of the tile edge.
Reply from Bryan at GreenGlue Company (within 5 minutes of my question!)
"Hi Rich,
I don’t think you'll need to drill holes. When you use the green glue you'll see that it's pretty viscous already and I would expect that even one layer will be enough to let it dry out.
I think that's a better option rather than drilling holes.
Best Regards,
Bryan"
"Hi Rich,
I don’t think you'll need to drill holes. When you use the green glue you'll see that it's pretty viscous already and I would expect that even one layer will be enough to let it dry out.
I think that's a better option rather than drilling holes.
Best Regards,
Bryan"
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Joined 2009
Paid Member
I made a big speaker using constrained layer damping. I didn't like the cost of Green Glue so I went off to find some MSDS sheets to learn as much as I could about what things are made out of. Green Glue is little more than Latex glue loaded with chalk (a common practice) and some jolly good marketing.
Latex glue is a commodity. There are different densities, manufacturers often load them with chalk (calcium carbonate) and MSDS sheets usually only give a range of values not exact formula. But you can buy latex glue at the local hardware store - which is exactly what I did. Good luck.
http://www.diyaudio.com/forums/full-range/217893-bigun-audio-nirvana-super-15-a.html
Latex glue is a commodity. There are different densities, manufacturers often load them with chalk (calcium carbonate) and MSDS sheets usually only give a range of values not exact formula. But you can buy latex glue at the local hardware store - which is exactly what I did. Good luck.
http://www.diyaudio.com/forums/full-range/217893-bigun-audio-nirvana-super-15-a.html
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http://www.certainteed.com/resources/CTG_GreenGlue-MSDS-Eng.pdf
Yup, latex dissolved in solvent. It's translucent when cured, so no chalk. Behaves like no latex adhesive I've ever used, still gooey and wet after 5 years air exposure, and test data proves strong damping ability. I have very small area to work with so I need the most damping constrained layer I can get.
You're right about the price, I have a tube leftover from a few years ago, but I was surprised to see the current price. Hopefully my old tube is still good. It's been out in the garage 40-90F, so maybe not.
I hope to get it done this coming week. Gotta rent a wet saw that can handle 18" tile.
Yup, latex dissolved in solvent. It's translucent when cured, so no chalk. Behaves like no latex adhesive I've ever used, still gooey and wet after 5 years air exposure, and test data proves strong damping ability. I have very small area to work with so I need the most damping constrained layer I can get.
You're right about the price, I have a tube leftover from a few years ago, but I was surprised to see the current price. Hopefully my old tube is still good. It's been out in the garage 40-90F, so maybe not.
I hope to get it done this coming week. Gotta rent a wet saw that can handle 18" tile.
Check out this
and this video. Very clear and distinct improvement in the green glue CLD panel. In fact, the difference is even more obvious in real life. The ringing goes down dramatically. I've tried increasing the non-CLD panel thickness to 3x, but the ringing stays the same. Only in the CLD green glue panel does the ringing show dramatic improvement.
green glue does stay extremely tacky and never seems to dry up, it's pretty much the best thing for CLD. Except that it's quite annoying to handle and clean up properly. I tried searching for the sikaflex adhesive but it's not available where i live.
the other important thing is that all the panels must have constrained layer damping. The best method you could try is to do mitered joints. That way you'll have a completely isolated inner and outer box.
and this video. Very clear and distinct improvement in the green glue CLD panel. In fact, the difference is even more obvious in real life. The ringing goes down dramatically. I've tried increasing the non-CLD panel thickness to 3x, but the ringing stays the same. Only in the CLD green glue panel does the ringing show dramatic improvement.green glue does stay extremely tacky and never seems to dry up, it's pretty much the best thing for CLD. Except that it's quite annoying to handle and clean up properly. I tried searching for the sikaflex adhesive but it's not available where i live.
the other important thing is that all the panels must have constrained layer damping. The best method you could try is to do mitered joints. That way you'll have a completely isolated inner and outer box.
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Paid Member
Bingo, that's exactly right. I made an inside box to hold the driver, and an outer box to go over it with the latex glue between them.
Dave,
Didn't you post a fair amount of info about "Constrained Layer Construction" on the old Bass List years ago?
Best Regards,
TerryO
I don't think I was ever on the Bass List, but I am sure I have stated this all before. Probably on one of the previous "ideal cabinets" threads.
One of my standard rants.....
These threads on CLD always stop just short of the exact construction details leaving the reader to ponder the last 10%.
I built a woofer with GG between two layers of 18 mm BB a couple years back and it seemed to work well but it was a pain creating the sandwich, waiting for GG to try and scraping off all the GG that leaked out the edges during the drying process.
I just prototyped a new box with 3/4" ultralight MDF w/o CLD. The box had removable sides because it was a proto and my first attempt at a complex build. I used 1/4" thick foam weatherstripping inside all the edges and on two window frame brace edges for an air seal. When I tested the box, all the surfaces except the removable back vibrated like crazy despite the good amount of bracing I had. Its interesting that the foam gaskets work so well. Those panels were completely quiet, at least according to touch. I wasn't any more scientific than that.
I can't use the foam gasket technique on all the surfaces because its ugly so its back to CLD with GG. I'm thinking of making sandwiches of full sheets of plywood and letting them cure before I cut anything. That should minimize the pain and mess. The finished box won't have the removable sides, just an access panel for the woofer.
This brings up the question of layer thickness. The original design was nominally 3/4" thick. In MDF, the total weight is more than I can handle without a dolly. I can't get the material I want in 3/8" thickness. I'm thinking I can go two 1/4" layers for the sides - its a triangular corner woofer and the sides will be in close contact with the walls- and two or even three layers of that for the baffle. But I could also do a 1/4" layer plus a 1/2" layer.
The outer layer will be a good hardwood plywood with a "stain grade" surface. Inner layer may be BB for weight savings but I could use MDF if it would work better. Opinions/ recommendations on layer thickness and materials?
I'm also wondering whether I should cut dadoes around all the edges of the final panels so that the inner layer floats. The illustrations in the tech papers usually show a floating inner layer but I recall a comment earlier in the thread that screws between the layers at the edges don't seem to matter.
Does anybody see a problem CNCing a plywood sandwich with a thin layer of cured GG inside. If the GG gums up the bit then I'm back to making panels the hard way. Seems like an experiment might be in order.
I built a woofer with GG between two layers of 18 mm BB a couple years back and it seemed to work well but it was a pain creating the sandwich, waiting for GG to try and scraping off all the GG that leaked out the edges during the drying process.
I just prototyped a new box with 3/4" ultralight MDF w/o CLD. The box had removable sides because it was a proto and my first attempt at a complex build. I used 1/4" thick foam weatherstripping inside all the edges and on two window frame brace edges for an air seal. When I tested the box, all the surfaces except the removable back vibrated like crazy despite the good amount of bracing I had. Its interesting that the foam gaskets work so well. Those panels were completely quiet, at least according to touch. I wasn't any more scientific than that.
I can't use the foam gasket technique on all the surfaces because its ugly so its back to CLD with GG. I'm thinking of making sandwiches of full sheets of plywood and letting them cure before I cut anything. That should minimize the pain and mess. The finished box won't have the removable sides, just an access panel for the woofer.
This brings up the question of layer thickness. The original design was nominally 3/4" thick. In MDF, the total weight is more than I can handle without a dolly. I can't get the material I want in 3/8" thickness. I'm thinking I can go two 1/4" layers for the sides - its a triangular corner woofer and the sides will be in close contact with the walls- and two or even three layers of that for the baffle. But I could also do a 1/4" layer plus a 1/2" layer.
The outer layer will be a good hardwood plywood with a "stain grade" surface. Inner layer may be BB for weight savings but I could use MDF if it would work better. Opinions/ recommendations on layer thickness and materials?
I'm also wondering whether I should cut dadoes around all the edges of the final panels so that the inner layer floats. The illustrations in the tech papers usually show a floating inner layer but I recall a comment earlier in the thread that screws between the layers at the edges don't seem to matter.
Does anybody see a problem CNCing a plywood sandwich with a thin layer of cured GG inside. If the GG gums up the bit then I'm back to making panels the hard way. Seems like an experiment might be in order.
constrained layer damping shouldn't use equal thickness layers of identical material with the damping between
its much more efficient to put the damping layer where there is more shear from bending - near the surface
and making the thin outer layer of the sandwich much stiffer to force the damping layer to shear is another mechanical requirement for good constrained layer damping efficiency
its much more efficient to put the damping layer where there is more shear from bending - near the surface
and making the thin outer layer of the sandwich much stiffer to force the damping layer to shear is another mechanical requirement for good constrained layer damping efficiency