Dear Thuchan and friends: +++++ " we all have spent a little too much in too many different solutions regarding finding the exact geometry for our tonearms............. for someone who deals with more than one tonearm/cart was calling for a universal approach " +++++
yes, a lot of time. IMHO from the point of view of tonearm/cartridge set up geometry there is no exact ( specific. ) geometry for a pivoted tonearm with slots on the headshell, let me explain it:
the only known " solution " to cartridge/tonearm geometry set up are the Löfgren equations ( 1938 ), all the other " solutions " are clones from Löfgreen ones ( Baerwald ( 1941 ) Stevenson ( 1966 ) and the like. ).
The original Löfgren was name it Löfgren A and is the solution that gives you the lowest possible amount of tracking error at the inner, centre and outer grooves while keeping this error equal at all 3 points. There is a small rise and fall in error between these points.
The second Löfgren solution was named Löfgren B and will gives you the lowest overall tracking error of any alignment method but with slightly higher error at the beginning and end of the record than the A method.
Both solutions are Universal ones and can be use it with any pivoted tonearm with slots in the headshell it does not matters the tonearm geometry design. If the tonearm is J or S shaped or what you " imagine " is not important for the set up.
This two Löfgren solutions/equations calculate ( in any set up ) the next set up parameters: overhang, offset angle, null points, linear offset and mounting distance.
These calculated parameters comes from the equations that have three known and only three parameters: tonearm effective length, most inner groove distance and most outer groove distance, there is no other single parameter need it or taked in count for the overall calculations: so the geometry tonearm design does not matters for this calculations, the only tonearm design factor important is that be a pivoted one.
Of course that you can make changes on this starting calculations parameters, this is that we can change the tonearm effective length for a different calculated set parameters or we can change the most inner groove distance tooo if we like it. Every time we made one of these changes we are changing too the traking error and tracking distortion values for that set up.
As you can see does not exist: that this or that kind of calculations is better for this or that tonearm, you are free to use it as you want: Löfgren A or B, there are no more, as I told you all the other " solutions " are mathematically identical to the Löfgren ones but only with different notation and arrangement.
It is ironic that for many of us Baerwald is more " familiar " name than Löfgren when was LÖfgren the creator of those two and only solutions.
The Baerwald solution is identical to Löfgren A as is the Stevenson B.
But like in many disciplines in the past and today exist the " false profets " that only create confusion/mix up but really does not add something new in favor of that discipline.
In numbers which are the differences between Löfgren A and B?, well the offset angle in both solutions are the same what is different is the overhang and by consecuence the mounting distance.
But do you know how much varies that overhang value?, around 0.4mm ( longer for Löfgren B solution. ) depending on the tonearm effective length.
Now, do you know how change the %distortion between Löfgren A and B?, well: máximum distortion between null points the difference is around 0.17% and the average ( over all the LP ) is 0.04%!!!!!
Do you think you or any one can detect those so low distortions differences?, certainly not. We need at least 1% of distortion to start to detect and no all the persons are so sensitive, there are persons that can't detect distortions on the 5% values and of course that depend which kind of distortion we are talking about but in general what we are talking on tonearm/cartridge set up we just can't.
I told you I own at least 9 protractors and any one of them is a Universal protractor but my ignorance in the past years made to ignore that fact ( universal ) and due to my ignorance level I followed to those " false profets " that taked advantage of my ignorance level and start to bought any single protractor out there.
Of course that there exist different protractor accuracy level that are important on quality performance but if the protractor accuracy is important there are other set up parameters that are important and critical, maybe more that the accuracy on protractors. At least two of those critical set up parameters are VTA/SRA and Azymuth and almost the 100% of the problems that many persons have with inner groove distortions and Shshshss on the voices recorded.
Let me tell you about: I never been very " anal " on the overhang/offset angle set up ( right now I'm using a 20.00 protractor with great success. ) but I take care a little more in deep on the SRA/Azymuth set up and you know what?, I never had/have inner groove distortion problems or exaggerated shshss on voices.
Thuchan, with that 20.00 protractor I just listened the 1812 Overture on Telarc where the most demanding score range ( cannons's shots. ) is at the inner grooves and the quality performance I heard was not only CLEAN but a great one!!!!, yes for me SRA/Azymuth are critical as is the own cartridge abilities to track along the tonearm it self.
I'm not saying that overhang/offset andgle/PTS distance are not important of course are important but there are a lot of things that define if we could have inner groove distortions or not.
Over the time I visited several Agoners places/homes like: F. Crowder, A. Porter, D. Deacon, S. Doobins, etc, etc , let me to tell you that in no one of this systems I heard inner groove distortions or exaggerate SHshshss on voices recorded and in no one of these places I see an " anal " attitude on protractors set up even in S.Doobins place he changed a cartridge using a protractor and taked 2-3 minutes to doing and even that that cartridge set up was not fine tunned everything performs first rate.
What I seen at those Agoner's places was a more in deep care for SRA/Azymuth/VTF set up even at " anal " level like in Doug's place.
Thank's God I learned ( actually, still learn every single day. )on the whole subject and in other audio subjects that permit that today I don't follow any more to those " false profets " or false myths created inside the AHEE because our ignorance level. Best medicine for this?: questioning always questioning ( what if that's not true or what if that white is not white? ) and testing, why? how? who? where? or just " please show me " prove me it's true.
Regards and enjoy the music,
Raul.
