Anyone have experience with this material?
https://www.menards.com/main/floori...e/405f014/p-1559630031755-c-1536584011607.htm
Rubber flooring used in gyms and training facilities. It is available in recycled rubber and rubber/cork composite... Price seems reasonable.
https://www.menards.com/main/floori...e/405f014/p-1559630031755-c-1536584011607.htm
Rubber flooring used in gyms and training facilities. It is available in recycled rubber and rubber/cork composite... Price seems reasonable.
My one experiment with it so far has been a quick fix of a plastic food container to a 6x4 inch piece of pine. The pine was quite resonant on its own, it made a nice dink dink noise when tapped. With the plastic fixed to it with this stuff it was pretty dead. When it dries it's a bit like chewing gum, and when pushed or poked with a finger it slowly moves back to its original position. My only concern is it seemed to dry out a bit after a few weeks. I think it will hold tiles up, it's sold as an adhesive to layer plasterboard together.
I shall add some information here although it has been more than a year since this thread has been active.
A good damping paste is Decidamp DC 30.
It may be worthwhile to explore their other products.
I have found a tip to this product in this YouTube video.
Besides some other sound engineering information this youtuber further demonstrates why plywood is more viable material for speaker enclosures than MDF.
All in all this guy has a wealth of knowledge of which audio is just a small part and which he happily shares. I would encourage anyone to like and subscribe to his channel. He needs support and deserves it too.
In my opinion MDF is cheaper material for loudspeaker manufacturers. It is easily machined with CNC so they rationale it with damping properties etc. etc. Particle board is cheaper still but unfortunately it is widely recognized as el cheapo material. Not that some manufacturers don't use it. They just slap some cheap plastic molding on the front and sing praises about special baffle material and shape resulting in sublime sound quality.
Now, some of my own thoughts on constrained layer damping (CLD henceforth). The basic premise is to have a lossy layer that gets sheared left and right. As panel vibrates it actually bends, so one outer layer is stretched and the other is compressed. The damping layer is constrained between those two plates (hence the name) and gets deformed in shear. If it is compliant and lossy it converts mechanical motion into heat. Gedankenexperiment: Think of a phonebook. Covers are outer plates, and the pages in between are your constrained layer. Now bend it and observe how sheared the CL gets.
From this it can be concluded that it does not matte how thick the cover plates are. What matters is that they are stiff in tension and compression. The can be actually quite thin. As explained below this can be even beneficial.
A panel can be CLD'd on both sides but for loudspeaker enclosures it is more practical to apply CLD on the inside only and leave the outside for lovely veneer of endangered tree species..
Different materials can be used for constrained layer (CL), Decidamp is one, another will be mentioned below. So how thick should the other plate be (the one on the inside of enclosure). As stated... not much. It is tensional stiffness that is important. I am bringing this up because above in this thread there was talk about using 1/2" plywood plate and 3/4" enclosure panel. That thickness can be used in better way to increase the thickness of outer enclosure panels. Those panels will be stiffer, miters and rebates can be made bigger and still have meat left. Whole enclosure will be beefier. Up to a point of course. No need to go over board. In your designed you can be constrained either by budget, meaning how thick of a plywood you can afford or weight, meaning how heavy loudspeakers you don't want to haul around. Use what you have in a way that maximizes benefits. A few milimeters (yes, that new thing called a metric system) thick plywood plate would be ok, thin steel or aluminum sheet would be even better, some commercial products even use aluminum foil. The point is that it is stiffer in tension than CL. Rubber sheet would not work as a constraining plate at all and because it is springy would not dissipate energy well and therefore not the best choice for constrained layer. Aluminium foil is also used (I think) because it can be shaped and applied to compound curves.
Another reason for using one thick and one thin plate hast to do with shear stress in CL. More is better. By using 1/2" and 3/4" with Cl in between your are moving CL towards the center where shear stress is zero. Absolutely worst idea is using sandwich of equally thick plates with CL in the middle. This would defeat the whole purpose of CL. The shear stress in center is zero, CL does not get deformed so it cannot convert mechanical energy to heat.
Speaker dave from Snell have mentioned that screws apparently did not have an effect on CLD. Others have concurred and rightfully so. Screws do not prevent CLD from working as screw compression does not oppose the principle. In theory they do restrict the lateral movement between plates, but this is negligible.
Interesting products from down under are from Megasorber are self-adhesive constrained layer damping sheet D14, self-adhesive vibration isolation & damping sheet DIS8 and self-adhesive damping tile DT2.
Demo on YouTube.
For experimenting I thing a brushed on bitumen layer (or heat gunned) with some this aluminium sheet (repurposed beer can) might be informative.
As for regarding other things in this thread. I do not get that ceramic tile idea. What is it for? For conversion of low frequency vibration into high energy so it gets more noticeable? Or is it to improve sound reflections so they can travel back into the speaker internals and finally radiate away through speaker cone, with time delay and coloration. One benefit might be mass loading. But mass loading is of little use in loudspeaker enclosure. It is good for sound barrier, but this is not good for speaker. High impedance mismatch increases reflection. Air ceramic boundary is good example of such. Energy inside loudspeaker should not be reflected (or it has to be reflected many times to be absorbed by stuffing and other damping). Energy just does not disappear, it has to be damped or it will go somewhere, either through cone or enclosure walls. And as we know, the later can be damped.
A good damping paste is Decidamp DC 30.
It may be worthwhile to explore their other products.
I have found a tip to this product in this YouTube video.
Besides some other sound engineering information this youtuber further demonstrates why plywood is more viable material for speaker enclosures than MDF.
All in all this guy has a wealth of knowledge of which audio is just a small part and which he happily shares. I would encourage anyone to like and subscribe to his channel. He needs support and deserves it too.
In my opinion MDF is cheaper material for loudspeaker manufacturers. It is easily machined with CNC so they rationale it with damping properties etc. etc. Particle board is cheaper still but unfortunately it is widely recognized as el cheapo material. Not that some manufacturers don't use it. They just slap some cheap plastic molding on the front and sing praises about special baffle material and shape resulting in sublime sound quality.
Now, some of my own thoughts on constrained layer damping (CLD henceforth). The basic premise is to have a lossy layer that gets sheared left and right. As panel vibrates it actually bends, so one outer layer is stretched and the other is compressed. The damping layer is constrained between those two plates (hence the name) and gets deformed in shear. If it is compliant and lossy it converts mechanical motion into heat. Gedankenexperiment: Think of a phonebook. Covers are outer plates, and the pages in between are your constrained layer. Now bend it and observe how sheared the CL gets.
From this it can be concluded that it does not matte how thick the cover plates are. What matters is that they are stiff in tension and compression. The can be actually quite thin. As explained below this can be even beneficial.
A panel can be CLD'd on both sides but for loudspeaker enclosures it is more practical to apply CLD on the inside only and leave the outside for lovely veneer of endangered tree species..
Different materials can be used for constrained layer (CL), Decidamp is one, another will be mentioned below. So how thick should the other plate be (the one on the inside of enclosure). As stated... not much. It is tensional stiffness that is important. I am bringing this up because above in this thread there was talk about using 1/2" plywood plate and 3/4" enclosure panel. That thickness can be used in better way to increase the thickness of outer enclosure panels. Those panels will be stiffer, miters and rebates can be made bigger and still have meat left. Whole enclosure will be beefier. Up to a point of course. No need to go over board. In your designed you can be constrained either by budget, meaning how thick of a plywood you can afford or weight, meaning how heavy loudspeakers you don't want to haul around. Use what you have in a way that maximizes benefits. A few milimeters (yes, that new thing called a metric system) thick plywood plate would be ok, thin steel or aluminum sheet would be even better, some commercial products even use aluminum foil. The point is that it is stiffer in tension than CL. Rubber sheet would not work as a constraining plate at all and because it is springy would not dissipate energy well and therefore not the best choice for constrained layer. Aluminium foil is also used (I think) because it can be shaped and applied to compound curves.
Another reason for using one thick and one thin plate hast to do with shear stress in CL. More is better. By using 1/2" and 3/4" with Cl in between your are moving CL towards the center where shear stress is zero. Absolutely worst idea is using sandwich of equally thick plates with CL in the middle. This would defeat the whole purpose of CL. The shear stress in center is zero, CL does not get deformed so it cannot convert mechanical energy to heat.
Speaker dave from Snell have mentioned that screws apparently did not have an effect on CLD. Others have concurred and rightfully so. Screws do not prevent CLD from working as screw compression does not oppose the principle. In theory they do restrict the lateral movement between plates, but this is negligible.
Interesting products from down under are from Megasorber are self-adhesive constrained layer damping sheet D14, self-adhesive vibration isolation & damping sheet DIS8 and self-adhesive damping tile DT2.
Demo on YouTube.
For experimenting I thing a brushed on bitumen layer (or heat gunned) with some this aluminium sheet (repurposed beer can) might be informative.
As for regarding other things in this thread. I do not get that ceramic tile idea. What is it for? For conversion of low frequency vibration into high energy so it gets more noticeable? Or is it to improve sound reflections so they can travel back into the speaker internals and finally radiate away through speaker cone, with time delay and coloration. One benefit might be mass loading. But mass loading is of little use in loudspeaker enclosure. It is good for sound barrier, but this is not good for speaker. High impedance mismatch increases reflection. Air ceramic boundary is good example of such. Energy inside loudspeaker should not be reflected (or it has to be reflected many times to be absorbed by stuffing and other damping). Energy just does not disappear, it has to be damped or it will go somewhere, either through cone or enclosure walls. And as we know, the later can be damped.
Last edited:
@Andrej
Shear stress is zero in the center of a bending panel? I think you are confusing bending/ tensile stress with shear stress. Google it and you will find that for any rectangular cross section it’s highest in the center and 0 on the surface of the panel/beam.
This is excactly why any guide on CLD describes equal stiffness on each side of the constraining layer; to maximize shear.
Any mechanical eng schoolbook will show you the example of two beams on top of each other in bending, with and without bonding between. From this it’s very easy to see how the constraining layer will be maximum shear in the center where the difference in elongation between upper and lower beam is at its maximum.
Shear stress is zero in the center of a bending panel? I think you are confusing bending/ tensile stress with shear stress. Google it and you will find that for any rectangular cross section it’s highest in the center and 0 on the surface of the panel/beam.
This is excactly why any guide on CLD describes equal stiffness on each side of the constraining layer; to maximize shear.
Any mechanical eng schoolbook will show you the example of two beams on top of each other in bending, with and without bonding between. From this it’s very easy to see how the constraining layer will be maximum shear in the center where the difference in elongation between upper and lower beam is at its maximum.
Last edited: