Speaker base - what material is best?

I suggest granite, and it can be found for pretty well nothing. Many folks are having granite installed as kitchen countertops, the cut out section where the sink goes is usually thrown away. Contractors usually convince customers to go with a particular color cuz they get a better deal that way, getting two matching pieces shouldn't be too hard. Track down a contractor who specializes in kitchens, chances are he'll give you a couple of pieces of granite gratis. Spend $50 to get them cut to size and the edges polished and voila! Just an idea, I did this and threw a chunk of granite under my turntable. Best, Jeff

Granite is the answer, go to a tombstone maker or other like ceramic's seller for kitchen or bathroom, you can put lacquer on the edge cut it's more cheaper than polishing and it give the same look and it could last long enough.
I use granite also under my sub Velodyne and all my electronics (Krell amp & SonicFrontiers preamp) are on a piece of granite on spike mount in a damping steel rack made all by myself, very heavy but very stiff and resonance free.
Between the floor and the granite you can use a one inch thick of felt, it's very good for damping and use spike on a wood floor it's not a good idea with several hundred pounds!!!
Also granite looks great :)

Hi Kubla, good to see U back. One word of caution re, stones. Marble can produce a mushy effect, while granite (that I'd prefer) can induce slight ringing. Of the two, granite has been the best performer along with Corian. On lighter pieces, however, Corian tends to shift the tonal balance upward (never tried with heavy equip).

Cheers!