Marble to place speakers on?

It should extend about 2" larger than your speaker, on all sides. I would suggest that you try at least 3" thick 4 is better. Now for the best coupling, attach the marble to bottom of your speaker. Have your supplier drill 3 holes about 5/8" diameter in a triangle pattern that will be covered by your speaker. Don't forget to have them counter sunk so the heads of the bolts won't be exposed. Use these for a pattern to drill holes through the bottom of your speakers. Now use a 1/2" bolt, preferably fine thread through the marble & the bottom of your speaker. The speaker will then be totally coupled with the marble, with the maximum effect. The effects of the bolting together will be noticed by rock solid bass, better focus, added detail. Simple as this is, it really works. I have my Duntech Sovereigns bolted to a 4" slab of marble, polished black to match the finish on the speaker. The results are outstanding. Good Luck!

Ditto to what Audio4fun stated on the benefits of marble, though I have heard dimensions of 4" additional on all sides to the dimensions of the speaker bases (i.e. 8" total greater dimension on all sides).

However, Duntech Sovereign speakers are about approximately 75" tall, 18" wide and 23" deep and weigh approximately 170 lbs apiece (I may be off a bit on these dimensions). Duntech Black Knight speakers for awhile came stock with a very heavy, dense base bolted to the main speaker similar to Audio4fun's stated method for his Sovereign.

Practically speaking, most speakers will have to settle for resting their spikes on a simple marble bass platform with the 2" larger dimensions stated by Audio4fun.

Also, I have been looking for marble for my current speakers and am finding it difficult to find a thickness in excess of 3/4". If you do find a source of a thicker marble please let me know.

By the way, expect to pay a premium for marble (or even granite). I am being quoted approximately $500 for two 25" x 20" x 3/4" slabs of polished Black China marble.

The best marble under speakers is the cheapest marble - ie. the marble with the most impurity. The impurity stops the marble ringing. Is is dolomite that is the impurity? I cannot recall - but I have tried different marble and the sound is better with the cheaper stuff.