Why do tonearm specifications list null points?

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.

Thanks for the explanation 

Dover, 

very good, and concise, explanation.  While the overhang for a different alignment scheme would result in a different angle of the cartridge that would not have the cantilever of the cartridge perpendicular to the axis of the vertical bearing of the arm, the difference in angle would be small, so that the imperfection would be more theoretical than practical.  There would be only a small variance in azimuth for different settings of VTA such that I would not worry much about it.  

@larryi Thanks for even more clarification - I was struggling a bit about the azimuth being thrown off but also concluded that it would have to be very minute.

While the overhang for a different alignment scheme would result in a different angle of the cartridge that would not have the cantilever of the cartridge perpendicular to the axis of the vertical bearing of the arm

This really brought it home for me and now it's clear why the manufacturer would list the null points in the tonearm specs 💡

I don't know if it's just psycho-acoustics or reality, but when I switched back the alignment from Lofgren B  to use the manufacturer's null points (virtually Baerwald), the soundstage magic returned...

Dear @jimmy_jet  : As a fact normally manufacturers did not write that spec because it's not really a tonearm spec and could makes ( as in your case. ) a " mix-up " for the owner.

Those null points means that one kind of alingment you can choice is the IEC standard Löfgren A and that's it.

" Soundstage returned ", well that's what you listen but not really a change by the Löfgren B because the overhang in between both alingments is lower than 0.5mm with the same offset angle.

Even the average distortions between both kind of alignment is around 0.04% lower in the LÖfgren B than in A.

What you listen is more a consequence of the tiny errors coming from the protractor and coming from our " hands " movements to the new set up. It's almost imposible to make a change in alingment making the same change 3-4 in a raw and achieve exactly the same grade of accuracy.

Regards and enjoy the MUSIC NOT DISTORTIONS,

R.