Decided to try a SPU cartridge

I don't think HTA = zenith.  The term HTA is relatively unfamiliar to me but as defined here it is the same as "Tracking Angle Error", the angle by which the cantilever deviates from tangency to the groove, TAE is the term I usually use.  TAE or HTA is changing as the stylus traces the LP and the tonearm rotates on its bearing.  Zenith is relatively constant, if the reference point is the LP surface.  I It changes as the TAE, if the reference is the orientation of the stylus in the groove, but it is not identical to TAE/HTA.  I am not planting a flag here, but it is a good idea if we all speak the same language.  I certainly can be wrong.

This whole HTA discussion highlights that if you want accurate alignment, you should only buy

- cartridges with conical/spherical tips

or

- cartridges that have a nude mounted square shank diamond and the cantilever has been laser cut.

If you are spending $5-10k on a cartridge, spend another $100 to have it independently inspected by a cartridge retipper. I have seen several $5-10k cartridges with styli mounted askew/cantilevers mounted incorrectly ( rotated ).

I'm planning to have all my cartridges reviewed by WAM Engineering - I'm of the belief that because of cantilever and stylus manufacturing alignment inconsistencies, the best way to align a cartridge is to get the stylus angle correct (vs aligning by cartridge body and/or cantilever).  IIRC. the resulting WAM reports will tell me how much the stylus if off perfect alignment so I can compensate by adjusting the cartridge body.  I'm somewhat concerned that some SPU tonearms may not allow zenith adjustment if needed.

@boothroyd 

The Rigid Floats fly in the face of all known theories of cartridge alignment, if you are using a standard style cartridge like the SPU Royal N the Nelson Hold headshell is a thing of beauty. Remove the headshell and just pop in a full bodied SPU and Bobs your uncle. It is one of the easiest arms to set up, the only slight issue is height adjustment which is easily overcome by using playing cards as shims. 

@kennyc 

The Kuzma 4points are fantastic arms the 9" is a Pitbull terrier of arm, with the 11" and the 14" being more relaxed, for the 11" and particularly the 14" you need to use relatively low compliance normal bodied cartridges and you can only use Nude SPU's. Are the Rigid Floats better? It comes down your own ears.

Strangely whilst mine is a 9" it's positioning is very close to that of a normal 12".

A general tip with Rigid Floats whilst in theory they are free standing they do benefit from being bonded to the armboard/plinth with double sided sticky tape or even better and if you are really brave gluing it with a few dabs of epoxy. 

What’s seems strange about the Rigid Floats is that they don’t give the tonearm mass which would allow cartridge+tonearm compatibility calculations. Rather, folks seem to be are using lighter to heavy cartridges.

Before I went down this SPU route, I was planning to purchase 2 tonearms. Originally my top choice was the 4point, then the next was a Schroeder CB or a Reed 3P. After reading about the different but excellent results the Rigid Float will be my second tonearm.

For a Ortofon SPU G type cartridge, I wonder if using the 4point or the Rigid Float are better choices than the other ~3k SPU tonearms I listed previously.

I favor the longer ~12 inch tonearms for their potentially superior sonics , not so much their higher price tags

All - thanks for your help and advice