VPI SSM lacking bite

My experience with TT is closer to your analogy of beach on mattress. I have an unsuspended VPI TNT on top of a heavy sandbox on top of large soft springs. It was the only way that I could definitively stop a knuckle rap to the rack below from traveling to the stylus. With this addition there was an obvious improvement in treble focus and smoothness. Now what is happening? Based on my arrangement of system, room, and rack, my speculation is that the springs absorb energy from inside TT as much as they isolate from earth-- perhaps even more so. Others have confirmed this speculation by testing the same system on a wall rack to further remove from earth and floor effects. The effect of long wavelength spring action is benign: I can force the soft springs into a gentle cycle of diminishing modulations without disturbing the arm or audibly effecting the stylus in motion. This forced low frequency long wavelength action is absorbing huge amounts of physical energy relative to what is generated from within the closed system of a TT and its motor. Why then should it not work just as well and remain stable when handling the much tinier vibrations generated by TT?

All sprung suspensions are not equal. Foot-steps across the room sets my lightly sprung Oracle TT on fire. But the massed-loaded combination of a 50lb unsprung VPI on a 100 lb. sandbox on top of springs behaves entirely differently.

A bigger sandbox is certainly better than a smaller one. But to complete the experiment, why not try even more decoupling?

I've been thinking about your spring arrangement for some time, I'm willing to give it a try. Should be good experiment with my wall shelf and huge sandbox. The only issue is determining which springs to try, I will have somewhere around 300+ lbs to support.

While I can understand the negligible effect of the springs on the movement of arm and stylus, not reintroducing vibration into tt, and greater de-coupling from external forces. I'm still not sure that internal tt vibrations can travel down springs into the stable surface below that, seems to me vibrations would get caught up in springs, both external and internal generated energy would be fighting each other in spring. I would think those vibrations would have greater drainage through the very sharp spikes I'm currently using.

I suppose the greatest isolation I could muster would be wall shelf supports made from a more aborptive material than my present steel supports. This would both serve to better absorb energy from tt, sandbox vibration sinks, sandbox, maple platform, and de-couple from external energy.

"I'm still not sure that internal tt vibrations can travel down springs into the stable surface below that, seems to me vibrations would get caught up in springs, both external and internal generated energy would be fighting each other in spring."

Physics suggests that the instantaneous vibrational forces applied at opposing ends of the spring(or any other coupling interface such as points, cones, or balls) act as oppositional force vectors. The difference between these force vectors from above and below represents the instantaneous force acting on the spring. This net force has a single direction and quantity at each instant. The question is, can the spring resolve this force into synchronous motion? If a vibration creeps all the way through the spring and is conducted between the interfacing layers, then the spring is "ringing" instead of performing its useful mechanical function of dissipating the vibration into mechanical energy. One way to address this ringing is to coat the spring windings in damping material such as sorbethane or an elastomer dip.

As usual your arguments make sense, I will try the springs. Now, any suggestions about what springs I should order for aprox. 300 lbs divided by 4 springs, ie. aprox. 75lbs per spring?

The springs I use are McMaster-Carr P/N 96485K125. They are 1-15/16”D x 4”L and use .148” diameter wire ground flat at the ends. They compress 23.7lbs/inch, up to a total deflection of 2.88”. So a 50lb load compresses each spring about half way down and leaves .88” of unused travel before the spring binds. I use six of them to support 200 lbs. This elevates the load 2.5" and provides a soft low-frequency bounce of around 2-3 cycles per second. For damping the central windings are wrapped in cut sorbethane also from McMaster-Carr. If you take this approach, get one of the stronger grades of sorbethane, as the thin stuff tends to split and unravel.