Tonearm mount on the plinth or on Pillar ?

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?

  

Those tables are so so cool looking. Love it.. A separate pillar would give you the option of a longer arm but the larger base with the arm mount in it looks like it makes the whole base large. I want one.

There is a long thread on this subject started by Halcro, in the context of which he refers to the idea of separating arm pod and plinth, which he favors, as "Copernican".  I vigorously disagree with him; I agree with Ralph (Atma-sphere) that the two should move as one.  However, I do agree with Halcro on many other subjects, and I consider him a friend. Ergo this point is no longer worth arguing about.  He and anyone else can do as they please, and I will do as I please.  We'll both be happy, I am sure.

I will just say one thing: Moonglum, your statement that the tonearm and plinth resonate separately even if they are locked rigidly together is kind of an oxymoron; if they resonate separately, then the goal of tying them together rigidly has not been met.  And in fact, I think a lot of designs are imperfect like that.  It takes a very substantial structural linkage to achieve the proper resonant unity.

I also think that if you bolt an outboard armpod to a rigid shelf and also bolt the plinth to the same shelf, you are doing the right thing.  The last photo I saw of Halcro's TT101 set-up looked to me like he was doing that; it looked excellent in fact.