Sandbox-style isolation

Assuming that significant mass loading has been applied to minimize shifts of the segmented top plates in the horizontal plane, the heart of the matter would seem to be that vibration is conducted through dense adjacent solids--in this case, mechanical energy moving in the vertical plane from plinth to footer to wood plate to sand. In a related twist, tonight I modified the suspension of my modified thread-drive VPI TNT to incorporate DIY Stillpoints inside the elephant feet (which are otherwise unsprung.) The mod consists of a pyramid of ceramic balls, supported by spring steel petals that dissipate vibration of the bottom tier of balls into the horizontal plane as mechanical energy. The result was a rather amazing improvement in coherence and general sonics. The operation of the ball/spring combo would seem analogous to grains of sand beneath the sandbox plates, but in the horizontal rather than vertical plane. Now I will bet my eye teeth that those balls & petals in the Stillpoints are by design moving more in the horizontal than the segmented plates in the sandbox-- and yet sound is significantly improved. You would have to put up a pretty strong argument that the improvement in sound represents a compromise between improved resonance control and degraded speed stability.

Dave, the sand should move in both the vertical and horizontal plane as well,

It still seems to me a mass loaded design should sit on the most stable platform you can provide, seems some non-sympathetic vibrations would be induced by more compliant platforms. Therefore, vibrations of different parts of the tt are moving asynchronous to each other, inducing confusing movement to the entire mechanism. Sitting on segmented plinths should only increase this confused movement.

I should add, every move I've made towards a less compliant plinth and more massive platform has resulted in increased sonics, specifically, much more coherence, solidity, slam and bass articulation. Any compliance sounds smeared and soft.

I plan on making a 10" sandbox this summer to gain yet more stability and mass. I'm also trying to find some wider aluminum L brackets in order to get more vibrational drainage. I always think about the massive plinths and platforms of the Brinkman and Continuum tts, I'm sure a lot of their superior sonics come from this mass and the stability it imparts.

"Any compliance sounds smeared and soft"

Lest the good folks misinterpret your comment, I'll embellish a bit.

The improvements rendered by reducing compliance result in both cleaner and more extended highs. There is nothing agressive sounding about the extended top end when you get this right.

Furthermore, the improvements are experienced as a richer, harmonic texture in instruments like acoustic bass. Bass texture is, after all about the upper frequency harmonics.

Again, it may well be that on some rigs, that isolating the motor can help in the way that a compliant belt can. Before you accuse me of heresy, hear me out.

In some AC motor experiments our little group of crazies has been undertaking, we positied that some of these drive systems might best be implemented with a compliant belt. There was too much vibration in the system.

Of course, we were looking at optimizing something that none of us would consider swapping out our rigs for, but the point is about trying to optmize given architecture.

There are no hard and fast rules. This was the source of my "ecosystem" comment and is the reason I'm not absolutist about one piece top shelves for the entire population of turntables.

I'm working on a source for some very stiff "L-brackets" which I used to source at an aluminum recycling yard. When I get the name for them, I'll publish it on both the shelf and stands FAQ section of my website as well as on the accessory page showing the sandbox made by Timber Nation.

Now, if you hang out at any electronic surplus houses, you might find some big honkin' heat sinks. I've come across some which are 6" x 8" and have some under my main sandbox.

Cheers,
Thom @ Galibier

Scott, I agree that sand moves in all dimensions at the particle level to dissipate system vibration as mechanical energy. The issue is somewhat different regarding drive train stability: Will the segmented top plates migrate or resonate in the horizontal plane in sympathy with transient pulling forces of the motor belt? Will any associated micro shifts in drive geometry introduce speed instability sufficient to off-set the virtue of improved isolation provided by a segmented top plate? One can only speculate on these matters until trying both arrangements with top-plates made from identical material.

Material composition is an important factor. For example, I first installed my DIY Stillpoints in cavities drilled inside the stock VPI delrin feet. Internal vibration was conducted from TT plinth to solid brass spacer plug(replacing stock sorbethane) to ceramic ball pyramid to spring steel bearing cup to delrin foot to wood to sand. Each modification was evaluated separately and was determined to be a sonic improvement. But the greatest improvement occurred after the final step of adding a brass core inside the delrin footer that directly couples the bottom of the ceramic ball bearing cup to the segmented hardwood top plate in the sand below. There is insufficient mass in this brass core to be significant as a vibration dump. Relative to delrin, the brass core must therefore be acting as an improved conductor of vibration down to the sand.

One might conclude that your aluminum top plate is performing a similar function as my brass core. Did you ever try the thick aluminum plate by itself to detemine if the plate is acting primarily as a dump, or as a superior conductor of vibration? If the sand adds any sonic improvement as compared to using the aluminum by itself, then one may conclude that the aluminum is performing as a conductor. And if the particular virtue of aluminum is its performance as a conductor, then one may speculate that your alum top plate also operates as a conductor of vibration in the horizontal plane between respective footers & motor. A superior conductor like an alum top plate might therefore benefit from segmentation more than other material compositions that tend to act as dumps. Segmentation may act to draw off the kind of "asynchronous" vibrations you alluded to above, that confuse a closed system where vibration is both generated & recirculated.

While it's nice to talk about reducing compliance as a absolute goal, I think this idea should be revisited in light of recent experience of jloveys and myself concerning the sonic virtues of Symposium rollerballs, Stillpoints, or my DIY version of same. These devices are designed to MOVE in horizontal, vertical, or both. I wanted to explore this with my recent TT experiment, and the results seem to suggest that mechanical systems like TTs need to "breathe" a bit to release energy. The result of this experiment is improved HF focus & smoothness, delineation of bass, and precise but rounded images-- anything but brittleness, softness or confusion.