Tonearm mount on the plinth or on Pillar ?

Ralph is absolutely correct. It follows that the tonearm and the platter must be in communication, and the faster the better. Beryllium anyone?

I think the theory of relative motion is simple to understand.  You don't feel like you're moving in a jet flying at 500 mph because you're both moving together at the same rate, so the motion sort of cancels itself out.  Something like that.  

pryso, i did not miss your point :)

Hi Pani
It’s important imo, to remember that the plinth is the lowest member of a base. When setup in this fashion the shelf holding "all the goods" becomes the plinth.
I went down this road many years ago, putting a tonearm on an isolated armpod/pillar. I was curious, it was fun, and it involved a lot of learning. I took the idea further using symposium roller block jrs., and a VPI JMW 12 tonearm. The original idea came from a Greek audiophile. I had so much fun I wrote a review of it, with a short youtube.

https://www.youtube.com/watch?v=HSZSzxnN1mg

Going by memory I can tell you that the cartridge used was very high compliance, Dynamic Compliance: 50 x 10-6cm/Dyne and when set up in the traditional way sounded terrible on this tonearm. But when set up like this; well you listen.

Pryso
Plus I live on the West Coast where we are subject to earthquakes, some of which go unfelt. I don’t want my tonearm "dancing" around somewhere close to the correct position.

Pryso
I am thinking the symposium setup might actually work for an earthquake, but I have no experience. I have experienced only a couple of shakes in Ontario, barely noticeable . What do you think ?


Chayro - I thought that was an interesting analogy. Some have tried to use the analogy of two boats floating next to one another. This analogy doesn’t work for me. An analogy that works better - I put in a heavy 20 foot long dock in the water one summer, and was so happy with the accomplishment I danced on the end of it. It barely moved.

I think I may need to offer a clarification on my reference to earthquakes. At least for those living with more stable terra firma who don't experience them.

My concern is not so much for movement while I'm listening (touche czarivey), although that is possible, but rather for shifting of the arm position whenever a quake occurs.  Since the table and arm (including bases) do not have the same mass their likelihood and degree of movement will not be the same.  And I may not even know the quake happened, and so to recheck alignment, but my system may not then sound "right" afterwards.

Of course as others mentioned there are other earth borne vibrations to be concerned with.  Is there a major highway nearby?  Any bus or large truck traffic?  Is there construction close to you?  And those are all external forces.  How stable is your turntable platform to begin with?