02-05-10: Donjr
Zargon. I'm just theorizing. It seems to me that slate or granite would resonate, where as MDF or plywood would not. If I were using slate or granite, I would put it on high density foam and not a lot of it, to cut down on how much surface area is touching the carpet. If you're going from having your speakers spiked to the floor (coupled) to putting them on slate on top of the carpet (decoupled), you will surely notice a difference for the better. Not the best though. You've still got something very heavy and dense, condensing the carpet fibers and slightly coupling itself to the floor, especially because of how much surface area there is with a slab of slate or granite. Companies such as Aurelex have done extensive research on this subject and that's why their line of products for decoupling amps (isolation risers) have very little surface area that touches the floor, yet very large surface area for the amplifier up top. The reason this phenom of slate and granite started was the WAF factor.....really. That's how this all got started. Then everytime somone posted the question, people would reply "I use slabs of granite. It made a big difference and it looks great", and everyone started doing it. I'm not saying it's a bad solution for carpeted floors, but there's better out there IMHO.
naah! I don't you have all the info/the correct info on the use of slate for isolation.
Due to the crystalline structure of granite, granite does tend to ring (& marble also exhibits similar ringing) when suspended (as in a rack). That's why some racks (Adona comes to mind) sandwich the granite between layers of wood. That basically damps the ringing within granite. OTOH, I've found that if granite is placed directly on the carpet there is no ringing in the granite.
Slate, if you look at its crystalline structure, is a very good isolation material. The structure allows for sheer movement & that provides very good isolation. And, as far as I could tell, slate did not introduce any harshness to the sound. Plus, as you stated, it has very good WAF.
Yes, there are many other solutions to isolation (as you stated) but don't discount slate as much as you have.
It might be better for you to stop theorizing & get the material into your system & do some listening?