Improving a stone rack

I share experiences with others, whereby adding granite slabs under components or (especially here!) speakers has had a significantly deleterious effect on sound quality. Harsh, bright, brittle sound. Just awful. 

Of course there are also known quality products where granite slabs / sheets have worked wonderfully. HRS incorporates granite in their platforms. Acora speakers (granite cabinets) sound awesome. I've got a friend with granite bases (sandwich design) for his Vandersteens - works great.

I think the most common theme for success is that damping needs to be applied over the full granite surface (at least 1 side). Iso Acoustics feet on 4 coroners isn't enough - I even tried that with my speakers and the granite slabs - no help. 

Herbie's sells (no idea of current availability) his "grungebuster" material in sheets cut your needed size, and I believe that's what my friend suggested for use in a sandwich with granite platforms. Seems reasonable to me! At least cover the top of each rack shelf, in your case. 

I'm looking to use a glass shelf rack, 5 shelves that sit in slots in the wood frame with a soft vinyl supporting the shelves. A Technics 1500c tt will sit on the top. If anything, what type of damping would work well on a budget? I was thinking of the stick on felt pads that you put on the bottom of chairs so they don't screech across the floor attached to the feet of the components. Too simple? How about an old tt mat cut into pieces?

Granite (sorry!)  I don't know how bad the rack is but it's probably not great. The turntable on top is probably the worst location, especially if you're on a suspended floor. Anyhow, try it all out first and worry about damping then. Otherwise you won't know if you've improved things. 

@ghdprentice 

I must correct myself- I think you’re correct that this stone comes from the Bushveldt Complex in South Africa- I just looked up the location in Google Maps!

My stone rack is made of Larvikite, found near Larvik in Norway, sometimes marketed as Emerald Pearl, or Blue Pearl. It is even claimed to be a Norwegian ‘national stone’ (though it is found also in Canada). I am sure that helps with the sound!

@noromance – yes, Nobsound springs may be interesting. I will first try my big Walker audio Valid points under the preamp, to see if they make a difference. Cerapucs might be even better, but aren’t high enough beneath the preamp to take over from the stock feet. You wrote:

«Are you assuming the shelves are ringing or reflecting the sound waves coming from the speakers, and adding a hardness? While that is valid, it’s not a major contributing factor. I’ve always thought of the challenge being more to do with the relationship between the supporting material and the component itself. It’s at that interface where the support-related sound quality is generated.»

Yes, I assume that the polished glass-like shelf surface plays a role. Somewhat like windows, changing the sound in the room. Although I don’t think ringing is a main problem. I would probably have to play music a lot louder than I do to achieve that. The rack is massive and inert.

I agree that the component / support relation is important. But how can I know if this is the main factor? Rather than reflective surfaces? These should be manifest in two different sound problems, no? In the direction of ‘glassy’ (reflection), and ‘smear due to vibrations’?