[andycsb]

Anyone tried solid wood (eg...walnut, maple, mahogany or rosewood) platforms under speakers and discovered that it changed overall tone? Description of change (positive or negative) would be most appreciated.

Thank you so much.

[Anonamemouse]

Anything that changes the height of the loudspeaker or that changes the distance from the units to the floor will change the sound. This is because reflections change. Also moving them forwards (always good) or backwards (usually not good) changes the sound and stage.

If you really want to place them on a platform I would go for something as solid as possible, marble comes to mind. Then use cork dampeners inbetween (really no use spending a fortune there), and you should be set.

[timind]

I used 2 inch thick platforms made from MDF with my Meadowlark Audio Kestrels. The platforms were solidly spiked to the floor and the speakers were isolated from the plinths with rubber feet. I can't say the difference was huge, but there was a subtle change in the tone. I felt there was a tad less bass energy which seemed to give the speakers a more airy tone.
I found a good deal on a pair of outriggers for the Kestrels which I thought did improve their sound. The outriggers also improved the stability of the speakers.

[JLM]

The best answer is to have heavy speakers and keep the volume to within reasonable levels.

Proper support is dependent on the subfloor. 

Speakers should be isolated from soft floors (like wooden joists over open spaces) to avoid transmitting sound into large resonant cavities, but truly proper isolation is very hard to determine/achieve.  The best isolation solution would be air bladders or magnetic suspension platforms but that leaves the speakers to vibrate (action-reaction of driver/air mass versus cabinet mass), hence the recommended heavy speakers and limiting the volume.

Speakers benefit from maximizing the attachment to rigid floors (like concrete) to reduce those self vibrations.  Spikes are only highly effective in the downward direction.  Bolting the speakers to the floor to really anchor them would be one solution.  Another would be to build the speakers/floor of continuous homogeneous construction (like a single pour concrete speaker/floor slab as found in a few giant bass horns).  Again short of that just use heavy speakers and keep the volume reasonable.

[witchdoctor]

Mapleshade Bedrock stands made a profound difference in my system. The bedrock stands are for book shelf speakers and they sell maple platforms for tower speakers. See my review:

http://www.audiocircle.com/index.php?topic=3251.msg26863#msg26863