Uni-Protractor Set tonearm alignment

Dear Jazzgene: VPI designer is a " weird/curious " person:

+++++ " VPI has conducted careful listening tests and determined that every
tonearm we tried sounded better with its mechanical anti-skating
disabled and the tracking force very slightly increased. "
++++

++++ " I did it by ear on my system, not by math on a computer. If you go by distortion you would never use tubes, only solid state " +++++

++++ " OVERHANG ADJUSTMENT:(FIG. 2 AT END OF MANUAL)
Do not go crazy over this adjustment. You do not know if the stylus is aligned
properly on the cantilever. You are also facing a constantly moving
target when playing a record. " +++++

yes, but he take it the work to build a protractor/jig to his customers where he states:

++++ " This adjustment will yield the lowest distortion in the last third of the record, the hardest to track, when playing a typical 12" record " +++++

Certainly not at random and fully by ears.

regards and enjoy the music,
raul.

OK, Harry listens & then tunes his tonearm.
But Daniel doesn't do listening tests, 'cause he doesn't have all these arms in his hand !
This example of VPI arms, proves the value of an alternative curve other than the standard Lofgren A or B or Stevenson, but Daniel do it on paper! just after knowing the dimentions & angles of any particular tonearm !
IMHO this is extremely interesting & arises questions about real new findings concerning the arm's body (shape-form-contour) construction, as designed & manufactured from it's inventor. Not bad at all, to accept & adopt a formula based on Physics and then apply the mathematics. Maybe this scientific theory could help tonearm designers to build better examples that serve & accommodate this demand from the begining of the production, by having the right shape.
Unfortunately this method remains still a secret and the validation by anyone could happened only by listening tests, after purchasing the UNI-PROTRACTOR with the requested special template.
I apologise if I haven't any clue about this, or even worst, if I don't getting the whole theme right and I've just improvise for the rationalization of these templates.

Dear Genesis168, sure enough Stevenson was not stupid - nor for certain is Harry Weisfeld. Both knew/know what they are doping and why.
BTW - Stevenson did in his calculation put the 2nd zero tangential error point ("null point") right at the DIN - respective IEC - cutting limit (i.e. innermost grooved area).
So the tracking distortion due to tangential error is always zero at the theoretical innermost groove.
This is per Stevenson's definition.
At this very same point Löfgren A is approx. 600% (6x) more distortion and Löfgren B is approx. 1000% (10x) higher distortion ( based upon that Stevenson is still say 0.1% tangential error distortion and not really zero ).
Löfgren did "sacrifice" the the inner groove for lower distortions between the 2 zero points.
This works especially well with shorter tonearms (9") and with records with long lead out groove.
He did not took into account stereo and did not dream about what wide-cut LPs some record companies would put out in the late 1950ies and 1960ies.
Many japanese audiophiles with 12" tonearms do align to Stevenson and for - again - very good reason.
With increased effective length of a given tonearm (especially so if the tonearm gets really long .. 11" and more) the Stevenson alignment's curve get's better and better vs Löfgren A (Baerwald) and Löfgren B.

In mountaineering you can usually choose between several routes to climb a mountain. Depending on your skills, periphery conditions, preference and experience. Each route has it's benefits and trade-offs.
Some do accept only the first, old and marked route and some do look for new routes.
Same here.
Cheers,
D.

Travbrow :
"A tracing arc with a specific distortion curve should have the same geometric error and distortions regardless of the arm, cartridge stylus or if the record is stereo or mono, I thought? "
Good question!
With our restricted knowlege till now, this is a fact.
So, what is going on with Daniel's proximity ?

If those 0 points mark the places whitout any distortion
why are we not able to hear them? One should akspect some
special (Aha!)feeling 'around' them. I myself would ply
only those parts on the records because my aim is perfection.

Regards,