Dear all, I would like to add, that in professional audio and engineering - at least here in "old" europe - the discussion about Löfgren, Baerwald etc. is long dead.
Löfgren and Baerwald did their calculations based on mono pick-ups and in a time when modern microgroove records were an idea of the far future.
A mono stylus has VERY different tracking conditions compared to a modern stereo stylus. Stevenson took this into account first and recognized the dangerous conditions towards the inner groove. In later years Rother, Kishimi and others further commented about this.
Among all these later (read: stereo era) engineers diving into the topic of tonearm calculation it was without question, that different tonearm geometries required different calculations.
It is always about effective length, overhang and offset angle. But it is also about grooved area, increasing diameter and resulting increasing difference between inner and outer groove wall, importance of lower geometrical based distortions in area of divergent tracking conditions.
It is all geometry, but for Löfgren and Baerwald (as a direct result of their time and the limited requirements) it was only a 2-dimensional model.
But a stereo groove is a 3-dimensional model and a very tricky one in the last 3rd of a grooved 12" record.
To understand completely what is going on, one must first look and comprehend the whole model - not just a simplified one without the most critical parameters.
This is true in tonearm calculation and as well in tonearm construction.
Cheers,
D.
