Why do tonearm specifications list null points?


I happened to be going through the manual that came with my Clearaudio Universal 12" tonearm and noticed they list inner and outer null points, 66.04 and 120.9 respectively, along with all the other specs. 

I was under the impression that tonearm geometry can be set to anything you want to use (Lofgren, Baerwald, Stevenson, custom) by setting it up with the specified spindle to pivot, overhang, and angle settings using a tonearm protractor, e.g., Dr Feickert, etc.

So, is the tonearm manufacturer trying to say that this particular tonearm is somehow optimized or was designed to utilize those null points they list in the spec?

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Showing 1 response by dover

So, is the tonearm manufacturer trying to say that this particular tonearm is somehow optimized or was designed to utilize those null points they list in the spec?

Short answer is yes.

In theory you can run any alignment you want eg Stevenson, Baerwald or even create your own. The headshell has an offset, but due to the slots you can rotate the cartridge and move it back and forth.

However the pillar bearings for vertical motion are offset to match the headshell  and if you use another alignment that results in the cartridge offset being different to the pillar bearing offset then you introduce issues where if you adjust VTA then azimuth will change at the same time. Each time you change VTA you will need to recheck azimuth. This is not ideal.