Any new ideas on an old theme?

The other day I checked at a granite seller to ask about soap stone. They will sell it for $58 sq ft. For my speakers I need 2 pieces 12x10 in. Like you Blindjim, I'm not sure about spending $120 for an experiment. I will look at slate this week. the problem with slate is it isn't perfectly flat on both sides.

yeah. There's the rub. Around here marble, granite, and one other I forget the name of now, aren't real expensive per precut piece. The problem is and I suspect they know it too, is their idea of precuts ain't my idea. Hence ya gotta have 'em slice and dice up whatever dims you need/want. Black marble, runs around 180 - 200 cut to 14x14 last time I checked, and that was a couple years ago now. I shudder to think what it could be now....

I wonder if they would or even have, a couple pieces which I could rent to try out... hmmmm. I never thought about that part. I think I will ask. Sure, if it is a good move, I'd go off for two pieces... cut and polished.

I wonder too, just how thick ya need to go with rock platforms for speakers anyhow?

If you don't need more than a 12" x 12" footprint, there's another much cheaper way. Head to your local Lowe's/Home Despot and pick up 6 flor tiles in your stone of choice: marble, black granite, etc. Epoxy three together to get desired thickness of plinth, with the added bonus of "constrained layer" technology. Heck, you could even mix and match granite and marble for the "zebrastone" look. Under $40 per side, including glue and tax.

There have to be bigger tiles out there too--e.g. 16" x 16"--but they're not sitting on the shelf at my local Lowe's. FWIW.

I agree with those above that if you have a suspended floor, you may well benefit from some isolation between the speakers and the floor. I had that problem in a previous room in spades as the floor had a natural resonant frequency around 32hz. After many trials, I found that a combination of slate under the speakers and a post under the center of the floor (in the garage) worked best.

I obtained 2 - 7/8" thick pieces of black slate 18"x24". The slate was heavy and relatively smooth (much more so that the slate typically used in a yard environment), however, as long as you have 3 spikes the smoothness is not critical. These pieces cut and polished on one side with finished edges were about $300. I also obtained an oil which when wipped on turned the slate a rich and shiny black which really looks great. To finish these off, I put some 12"x12" self adhesive vinyl tiles from HD on the bottom of the slate cut to fit. This allows me to move the speakers around on the carpet much more easily than with the relatively course unpolished bottom side of the slate.

The heavy slate on carpet/pad gave the needed isolation while still providing stability. The floor resonance was dramatically reduced and the bass tightened up considerably. This same result may be possible with slabs of heavy wood or butcher block as well, and I will be curious to learn what you find out.

I just placed a buy it now on ebay for two pieces of granite, 12x12x1.25 in. I'll be sticking them under my speakers and probably use blu tac between speakers and stone. Will get back on the results.