Spindle-To-Pivot Distance

Lewm you brought up the question  that 1st popped  in my head.   Could you move it  10mm  and still have 2 null point.  With the calculator  on vinyl  engine  you should be able  to solve with the variables  he knows.  He could also go to vinyl  asylum  and ask John Elinson (sp)  he has his own spread    sheets.  He could figure this out quickly  and will recommend  to play by the rules.  

As a side note I have been playing around with 2 of my 14 inch arms  with no offset  and 1 null point.  Seems to be a little more dynamic.   If the average distortion is higher  it  is not apparent.   Need to really  sit  down and listen and go back and  forth.   Took up  Kayaking last year  so haven't  been building and listening much.

Enjoy the ride
Tom

PS.  I like the looks  of a cartridge  all the way forward in the head shell.  Although  I  don't remember  the OP  asking  about  this issue.

Dear @mrearl :"" Suppose I have a tonearm that wants to be mounted 250mm from the spindle . ""

first that all is not that the " tonearm wants ", that could be the manufacturer spec ( normally the manufacturer gives the tonearm EL. ) and nothing more than that.

If you need to mount from the spindle at 240mm what you are doing is changing not null points but tonearm effective length, overhang and off-set angle.
So what you need is that the tonearm/cartridge new alignment be made it with a new overhang and offset angle.
A shorter effective lenght gives you a little higher overall distortion levels that maybe you can't even be aware of.

Here the parameters value you need for 250mm and you can choose between those 3 alignments:

https://www.vinylengine.com/tonearm_alignment_calculator_pro.php?arm1=Arm+1&l1=ps&a1lv=250&a...

here for 240mm:

https://www.vinylengine.com/tonearm_alignment_calculator_pro.php?arm1=Arm+1&l1=ps&a1lv=240&a...


If you use a good protractor then normally there will be no cartridge mistraking.


Btw, it does not matters the changes in tonearms EL the null points inside each type of alignment: Lögren A or B or Stevenson always are the same.

In 1938 Erik Löfgren stated over his calculation equations to find out the cartridge/tonearm overhang, off set and the alignment null points where the input parameters in his equations were and are: tonearm EL, innermost groove and outer most groove distances and the equations outputs: overhang, offset angle, null points and by difference P2S distance.


Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

I always wonder what sort of (mono) systems were available to Baerwald and Lofgren in the late 1930 or early 1940s, when they published their analyses, and how their work applies to modern stereo gear. Yes, geometry is still geometry, I know.

TomWh, I own an RS Labs underhung tonearm, and it is my experience with it that leads me to be a bit nihilistic when it comes to alignment algorithms.  What 14-inch tonearms with zero headshell offset are you using? I guess I assume you mount them so as to underhang the spindle. (Meaning the stylus tip does not overhang the spindle.)

Been mathematics alignment overall parameters can be manipulated by any one and only has to make the new calculations for the alignment.

As a fact the Stevenson alignment comes by Stevenson parameter manipulation using the Löfgren equations: he took the equations input " most inner groove " distance and converted it in the inner null point.

R.

Lewm  the arms are my own.  The ones with the zero offset  are Brazillian  rosewood with a straight  aluminum headshell.  I use a spacer block of aluminum  or wood for now, between the cartridge  and headshell,  so any angle is available including  zero.   Better check the blood pressure  at the rigid camp.  In fact if you showed them your  RS tone arm you would have to take them to the emergency  room after they see the headshell can move.  Need we forget it wobbles  with no silicone  and  the  pivot is  no where near where it should be.   

The 2 arms are  the same table.  One is rigid on plinth  the other on a massive pod.  Oh dear  the rigid camp is going to lose it.  Now  something that make a real sonic difference  is I can run my tables  either  belt/tape or  idler.  Can change back on forth  around 5 minutes.   Even the  density  and thickness  of the o'rings can change the sound.  Go Figure!!!

Well I went a little  off topic but I hope  the OP gets  what you brought up  about  Did the so called Masters of the old days, using mono,  know  what sounds the best or just like whatever the machine told them.

Enjoy the ride
Tom