I built this for a Rega Planar 3 that had a rumble problem. Here is one of my design drawings.
Daruma isolation bearings were made by Final Labs. While this is an isolation box, it worked more for damping the table than anything else. The motor generated vibration the high output cartridge picked up easily even at low volume. So, apply a little physics. Glass is a great conductor. It allowed the table vibration (mechanical energy) to excite the glass beads that dissipated it as heat (electrical energy). Like rubbing sticks together, but on a finer scale like a million micro sticks.OK I'm an old man, but a newbie here, but what the are Daruma insets? Obviously some sort of foot or isolation device, but ??
It is a great looking base. As I see it, it is a large mass with shock absorbing feet. Where was the "rumble" coming from? If it was from the turntable itself, as I see it, this would work if the rumble was resonating with whatever base the turntable was previously setting on. If it was from an outside source this would possibly be a good isolation device. But regardless, as they say, "if it works", it works, as well as looking good, just don't let those glass beads get into the mechanics of the turntable!
The Grumpy One
The ball bearing isolation is what the Daruma Isolation bearings are. One cup is concave and the other flat inside. Your contact area is small giving you the isolation.In another forum (not HTS) awhile back, someone was talking about creating isolation by using a steel ball bearing 1" diameter or so in a slightly concave dish, say 2" across, one of these at each corner of a piece of equipment - speakers to begin with, then other pieces of equipment where vibration could be an issue - turntable or CD player. Said it gave a big improvement in imaging. I know this is a bit different from what you are suggesting, but any experience with isolation of that sort? There was even some discussion about mag-lev bearings and air bearings throughout a system for the same purpose. Any feedback/experience with this?