Here’s a question directed at the very small group of LP/turntable/pickup arm/phono cartridge designers/retailers/installers/enthusiasts who can make sense of it!
I just acquired a Zeta arm in great shape, which is however missing the thinner of the two weights included in it’s counterweight. For most users, a garden-variety steel washer would provide an easy solution, as that is all the missing stock disc is. And I may do just that. But for my assembled record player components, I need to do more. The need arrises from the fact that:
1- The arm is going on a Townshend Rock table, which requires the mounting of two "outriggers" and a tubular "paddle" (the mass of which totals 11 grams) to the headshell of the Zeta. The mass thus added to the front end of the arm requires comparable mass be added to the counterweight, as the Zeta’s counterweight, even positioned on the arm as far back as possible, cannot balance the arm with the added mass on the headshell. Adding mass to the counterweight raises the effective mass of the arm, which is 16 grams. Effective mass introduces the consideration of cartridge compliance and cartridge/arm resonant figures, which brings up the second complicating factor in my particular situation:
2- The cartridge is a London, with compliance figures of 10 vertical and 15 lateral. The differing vertical and lateral compliance figures results in differing resonant figures. I calculated those figures as 7 lateral and 8 vertical, a little lower than optimum. Luckily, the damping provided by the trough system of the Rock table mitigates those figures somewhat. But it occurred to me that as long as I am adding mass to the counterweight (I have no choice---there is no way around it, even though it lowers even further the resonance figures), perhaps it could be done in such a manner as to add as little as possible. I was thinking of sticking the little lead weights (around 3/16" x 3/8" x 1/8" thick) found at bait & tackle shops onto the backside of the counterweight (the lead weights have double-sided tape on them), placed in a vertical line top to bottom. I believe that will keep the mass more in the vertical plane, less in the lateral, which will be best in relation to the compliance of the cartridge.
Thoughts, anyone?
