Why do tonearm specifications list null points?

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.

Several years ago, I experienced the issue discussed by Dover and Larry with a Dynavector DV505 tonearm, probably because the DV uniquely places the vertical pivot so far forward from the horizontal pivot.  The DV was designed with headshell offset for Stevenson or something very close to it.  When I aligned a cartridge according to Baerwald, I of course had to twist the cartridge in the headshell so that its long axis was deviated toward the spindle. I was unhappy with the resulting SQ.  Reasoning that the problem was due to the necessary misalignment of the cantilever with the vertical bearing arc, I then straightened out the cartridge using Stevenson.  Whether this hypothesis for cause is valid or not, correcting the alignment of the cantilever to be in the same plane as the arc of the vertical bearing made for a big improvement in SQ.