Eminent Technology ET-2 Tonearm Owners

Apbiii - Martin Colloms did some testing of energy transmission in the ET2 years ago. He measured the resonances in the arm tube and then in the arm after the air bearing. The conclusions were that the unwanted energy transmitted went straight through the air bearing and out the other end relatively unimpeded.
This is the old chestnut - do you kill unwanted energy by overdampening, or by having a drain path to ground ( the plinth ).
The main issue with overdampening is that soft materials eg rubber, will store energy and then release it "out of time" with the music, thus smearing the sound.
People will have their own preferences, do you want to hear everything, quick, coherent, lively if a little coloured, or do you like a nice smooth inoffensive sound if lacking a little speed, detail and coherence.

Dover,

Just to clarify-

The conclusions were that the unwanted energy transmitted went straight through the air bearing and out the other end relatively unimpeded.

Do you mean that the energy went from the spindle, through the air gap, into the manifold, and into the plinth?

From the arm tube to the plinth and the energy resonances measured were very close, ie transmission rate was very high.

An interesting set of articles on the ET2 with a little discussion of resonance in tone arms.

http://www.stereophile.com/content/eminent-technology-two-tonearm

I have not thought much about the actual mechanics and physics of turntables and arms but some of what I read does not make much sense to me. Perhaps someone can help me understand better.

Folks talk about "draining" energy to the earth or some other place of stability as if it somehow removes the effect. This does not make sense to me. If a tone arm resonates at some frequency it seems to me that it must be moving. That movement will eventually be damped by some mass, i.e. the movement will become undetectable. The resonance will if no longer being excited die out as the energy is dissipated as heat energy raising the temperature of the resonating part.

The damage from an audible perspective would seem to me to come from the movement. For the cartridge to reproduce what is in the groove it needs to be absolutely fixed relative to the groove. If it moves relative to the groove then that movement becomes part of the electrical signal as there is no way for the cartridge motor to know if the cartridge is moving or the cantilever is moving.

What I think Bruce is saying with his measurement technique is that if you can sense movement in the headshell of a tone arm, which is what you are doing by placing another stylus / arm on the headshell as it plays a record, that movement has to be counterproductive to the faith-full reproduction of the information in the groove.