Torsional vibration; Gimballed vs Unipivot

[James D]

Steven,

Yes, the old Arcos beauties were nice looking and inspirational. I'm planning a flat arm like that, I think for a unpivot it will work nicely - like the Scheu Cantus. To get back on topic, it should help by increasing the torsional moment of inertia and provide enough headshell mass for a 103 :-). The only issue I'm not sure of is how to control the lateral resonances through the flat plane of the arm. Its a bit like the panel vibrations in the Quasar OB frame. There I allowed then to happen but ensured that the dimensions were constantly changing so the vibrations were wideband and low amplitude. I'm not sure that will be the right approach for a tone arm...


James

[steve s]

Originally Posted by James D

Steven,

Yes, the old Arcos beauties were nice looking and inspirational. I'm planning a flat arm like that, I think for a unpivot it will work nicely - like the Scheu Cantus. To get back on topic, it should help by increasing the torsional moment of inertia and provide enough headshell mass for a 103 :-). The only issue I'm not sure of is how to control the lateral resonances through the flat plane of the arm. Its a bit like the panel vibrations in the Quasar OB frame. There I allowed then to happen but ensured that the dimensions were constantly changing so the vibrations were wideband and low amplitude. I'm not sure that will be the right approach for a tone arm...


James

you 've got me at it now.. the best way to control all the resonances is by using a tube..?.. and the unipivot balance point should be way above the arm to control any off axis rocking.. sort of mounted on a pendulum...mass has more effect at a distance...

I'm getting carried away now..

and this logic is full of holes

steve

[James D]

Naw... all a tube does is tunnel and focus the resonances Actually if you look at the resonance peaks on a tube compared to a an irregularly shaped flat arm then the tube has much more spikes and at higher amplitude...

And if it's a metal tube then these resonance spikes are more prominent right where the ear is most acute...

and don't talk to me about rigidity - how rigid is a thread? Yet the Schroeder style arms sound great. There is more going on here (hear?) than our simple models acknowledge

Good fun though!!!

James

[david counter]

I always knew playing vinyl is an intellectual challange, if it was simple like playing CDs just think how bored we'd get,