I have experimented with isolation materials. Hard surfaces like granite, glass, etc is going to emphasize the treble freq. Soft material IE Vibrapods, sorbothane will soften the highs but often at the expense of clarity. Muddy sound come to mind. A tone wood IE maple is the best I have found. I've also used DIY roller ball type footers with good result. I recently changed from those to springs and saw no degradation to the sound.
Improving a stone rack
Hi all, I have a large stone rack for my system, in beautiful granite, which works great for stability, but maybe not so good for other aspects of the sound. I wonder if it contributes to some treble ringing and harshness. I want to improve the sound, thinking of felt damping on the wall behind the rack, some form of cloth to cover the reflective surfaces of the shelves, and adhesive rubber type mats on the bottom of the stone shelves. Is this the way to go? Experience based advice is very welcome. My rack weighs a ton. It is not easy to compare to a wood or composite rack. I need advice on how to counter the sound problems of stone or similar polished surface shelf racks. I want to try this, before I consider a new rack or shelf arrangement.