FR64s & Orsonic Av-1s Effective mass ?

Interresting debate!

Got the Orsonic AV1S after some busy days with barbequing, beers and music. There must be no doubt that the AV1S was a much better match than the original FR64S headshell with the Super Gold. It sounds smother, cleaner and dynamics is really kicking. It is quite fun to drop the Decca needle now. And amazingly, the hum totally dissapeared😃!
According to HFN test record the ressonance are now about 9 hz. Still tweaking..

I should mention that I guess the relative good result also has to do with  the vacuum ( flat record/ no suspencion cantilever) and " oil spring damped" plinth/ Basis Debut..

As I implied in one of my responses to Raul, I think the coupling of the tonearm (any tonearm, but maybe especially undamped tonearms) to high mass is another form of dampening.  So, you're on the right track, IMO.

Yes, I was thinking about on what You wrote about the B-60, offloading the vibration energy. An interresting theory. By the way I do not have the B-60, but the arm is drilled directly in the Debut plint.

The fr64 is an excellent arm. Raul has some strange opinions some times. I think he loves distortions😱