You will drive yourself crazy trying to tune your system with different media in your stand. Lead, sand and cat litter....I've tried all three at various times, even combining them at different rates. I look back at all the crazy tweeks I have tried and I shake my head. Nothing was too far out to try. And I now believe that the general consensus that a good rack will "make" the system is flawed. The combination of variables are numerous. Let's start at the beginning: strong wood floor/weak wood floor/concrete floor, steel rack/wood rack, filled tubes/empty tubes, spiked rack legs/no spike rack legs. How about shelves?...Black Diamond, Polycrystal, mdf, plywood constrained layer, granite, cedar, maple, glass. Do you spike the shelves to the rack or not? If you do, will you use brass, aluminum, ceramic, composite or Black Diamond cones? All of this is a balancing act of resonances which I admit will influence the sound of the component....but only if it is in contact with the component! That is why spiking components to the rack is ultimately a flawed approach. The solution is to not spike components to the handful of resonances residing in all racks but to isolate the component from the rack. When you do this, you now make it simpler to tune your system. Use the rack to hold your components but do the tuning part at a more intimate level and you will find that the results are more easily controlled and predictable at all frequencies. After trying to juggle all these combinations of resonances over the years I have settled on Herbie's Tenderfoot w/ebony balls. The Tenderfoot is a squishy proprietary material which holds the 1" ebony ball. It is this first contact point up against the bottom of a component which is the most critical when tuning a system. After years of chasing down and trying to control nasty resonances with fancy fandango footers, I can say without a doubt Herbie Tenderfeet w/ebony balls are the best. Herbie also offers hard maple and a hard rubber type ball for alternative tuning options but I find ebony to be the best material for my components. Since the balls rest on the Tenderfoot, no vibrations or resonances can come up from the rack and it seems the the squishy Tenderfoot material has a near zero influence on the sound of the ball which is contacting the underside of the component. Controlling resonances directly at the component level is much easier than finding the right combination of the many variables found in all floor/rack/shelf set-ups. I would still advise to fill the stand with something easy like sand, but only because it will kill the metallic ringing sound you hear from sound waves hitting and bouncing off of it.
