Improving a stone rack

Try using a very dense wood that has a totally different sound signature from the hard granite in conjunction with the granite.  I've tried many different types of materials for a rack.  I have been using a pair of Sistrum racks from Star Sound for many years.  Anything that is placed on it immediately sound more live but without ringing or any other sound issue.  I also use RTS couplers to clamp each component to its shelf.  The combo is about twice as effective to improving the SQ as the Sistrum rack alone.  I was very lucky to have a former owner sell me all his Sistrum racks used at very good prices.  You can even install this racks between the speakers with little or no drop in soundstage info.  My two racks are about 18" behind a line between the two speaker fronts.  They allow so much air to circulate w/o ringing vibrations behind heard it's wonderful.  Used they are MUCH MORE affordable.  Thanks Al Jennings.

Bob

“African black granite” is not granite but instead fine grained gabbro. It’s denser than granite, as different minerals make it up. No quartz, and denser, more calcic plagioclase feldspar, and relatively dense, iron rich pyroxene. I am retired now, but I was a volcano guy and used to analyze igneous rocks. Catchy trade name, though. I agree that this material really works for speakers, as all the Acora speakers I have heard are really special. And the owner is a truly nice guy, who I am delighted with for buying Audio Research. 

@jallan I’m not as well versed on granites and types of rocks as you, just going by what I was told. I don’t doubt anything you’ve said. I definitely agree that Valerio Alcora is a very nice guy and great rep for his company. I emailed the company with a question regarding setting up the rack and he actually called me himself and walked me through it. This rack weighs about 250lbs w 5 shelves and definitely improved the sound. 

I remember the first time I heard his smaller speakers-it was 2017. I was more impressed by the sound that they were making than anything else in the Capital Audio fest. Of coarse he was running Audio Research gear- Ref 6 preamp and the 75 ref amp, and it was glorious. And honest guy. It was the real deal. If I could afford it, I wouldn’t hesitate to buy from him. I have just never heard any real flaws in his products, they sound fabulous.