What considerations apply to material selection for cartridge mounting bolts?

Have you guys tried this resonance calculator? I found it helpful when I was looking for a cartridge that would work well with the tonearm on my Luxman turntable. If your cartridge's weight is expressed as um, type (it's__um = dynamic compliance) in your browser's search bar and it will calculate the figure in Hz, then you can find the intersection on the table for your arms total mass including your cartridges weight.

The golden range may not be exact as expressed in the graph but you'll get very good results when you test your resonance vertically and horizontally with a test record. I got 10Hz vertically and 9Hz horizontally.

You should also consider the weight of an optional counterweight as I did since the cartridge I chose (9.5g) was at the upper limit of the tonearms standard counterweight, so I purchased the optional heavy one. This helps keep the counterweight closer to the gimble improving the distribution of mass.

https://www.vinylengine.com/cartridge_resonance_evaluator.php

@faustuss 

No worries, cobber!  (I'm really a ten-pound-pom anyway - though I have been neutralised).

Thanks for the resonance tip.  Still learning this stuff.  I have not tried the cartridge resonance calculator yet, but I will.

It is a bit challenging because for most arms, there is only one effective mass.  The Holbo has two - vertical and horizontal and they are very different.

The 70-kg squishing my Sorbothane probably resonates at under 4-Hz

I do have a Tacit test record and an oscilloscope, but I think I have to brush up my German to make much headway.

Playing the test record without the ’scope, there were no obvious audible resonances on my Holbo system ...

@richardbrand 

In my haste to throw my two cents in I keep ignoring the fact that that you're trying to optimize a tangential arm and not a static one.

I was referencing to a resonance test that is manual using visual observation to determine the arm assembly's actual resonance frequency using a swept tone in phase for horizontal and out of phase for vertical where the tonearm and cartridge assembly will visually oscillate at whatever the natural tendency is for that mass and compliance. It would require some form of intervention if not in the optimum range.

Since I haven't a clue regarding the operation of a tangential arm I'll defer but hope anyone who happens on this thread will find our exchange useful to their endeavors setting up a traditional tonearm. Thanks for your consideration anyway.

RB, off the top of my head I am not sure you’re correct regarding horizontal effective mass for an LT tonearm, because there is still a distribution of mass between stylus tip and the air bearing such that mass near the tip is more readily moved than mass at the bearing. I think it would still depend upon the distribution.As you said most of the mass is at the distal end. I have not looked it up on ChatGPT or even the internet in general. Just guessing.

@lewm  outer tube

On the Holbo, as opposed to servo-driven tangential arms, the entire arm assembly including the air bearing outer tube acts as a single rigid mass.  The bearing outer tube is about 70-mm long, while the business end of the tone arm is just a tad over twice that, forming a rigid T.

The cartridge end really only has two degrees of freedom, because of the T-shape and 10-micron tolerances.  It can only pivot precisely vertically, and it can only slide precisely horizontally, on an essentially friction-free air-layer.

When the stylus moves sideways, it has to act on the entire mass, no matter how distal or proximal each bit is.  There is no need to even introduce the artificial concept of effective mass.

One consequence of the design is that there is virtually no fore-and-aft movement at the cartridge so nasties in the groove like scratches and dust don't set off sympathetic rattles.  The cartridge cannot rotate in any plane except vertical, which it has to do to ride warps.

No matter how closely I look, I cannot see any jerkiness or stiction whatsoever in the sliding motion. Quite brilliant design, in my opinion