It is designed to shear under deformation(vibration) and in this process lose the energy created by vibration. Isn't that what a constrained layer damping assembly does?
Well, yeah, that kind of is what I said, isn't it?
Green Glue is designed to damp resonance between sheets of drywall. But it is not designed to DECOUPLE them, which is what you want for a speaker stand. It damps drywall layers very well, because it is designed to be a constrained layer damping material for drywall.
You gave the long, technical explanation, which is correct of course, while I gave the abbreviated layman's, version. (We seem to have our roles reversed there!!!
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But constrained layer damping is not what you need in a speaker stand. You need decoupling.
The thickness of Green Glue between two layers of drywall is, according to their web site, practically nothing. It comes out of the tube quite "runny", and ends up as a very thin layer between the drywall sheets. Between two layers of porous concrete, I reckon it would be even thinner! I don't see how it would be able to decouple them.
The way I see it, what you need for a speaker is to decouple it completely from the stand, not just to damp the resonance with a very thin layer underneath it. Most designs I've seen for speaker decoupling use neoprene, rubber, or foam for that purpose, or even some kind of suspension system. It's the same basic concept as walls and ceilings: Mass-Spring-Mass. You need something to act as a spring between the mass of the speaker assembly above, and the mass of the stand assembly below. Neoprene, rubber, and foam all make good springs in that application, if you load them correctly. Green Glue isn't thick enough, and isn't designed to be a spring. As you correctly pointed out, it is design to be a constrained layer damping material.
If you think it would make a good decoupling spring for speakers, then what degree of compression do you think would be appropriate? Should it be compressed 10%? 20%? More? Less? What loading would you need to get that compression? The manufacturer of Green Glue does not publish that data AFAIK, so I don't know where you'd get it. (My guess is that they don't publish it because their product is not designed to be a speaker decoupling spring!)
As with all MSM decoupling systems, getting the spring loaded just right is the key. Load it too much or not enough, and it will flank. If it flanks, your speaker is coupled to your stand. Without that compression and loading data, I don't see how you can build such a stand, even if you assume that Green Glue does in fact have useful properties as a speaker decoupling spring.
IMHO, using Green Glue for something that it wasn't designed to do, about which the manufacturer makes no claims at all (and provides no data), doesn't seem like a good idea: After all, if it really DID work for decoupling speakers, then I reckon they would have figured that out by now, and would be talking about that in their marketing, and providing the same amount of data as they do for the normal application of damping drywall resonance, as another way to sell more of the stuff! But they are a careful company, from what I can see, and they back up their claims with solid data from testing their products in independent labs. So the fact that they make no such claims suggests about their product doing well as a speaker stand decoupling spring, and the fact that they don't provide the data that you'd need in order to use it for one, suggests that it probably doesn't do what it wasn't designed to do.
- Stuart -
