Ready for a truly hot topic?
Which alignment do you prefer, and why? -Stevenson -Baerwald -Loefgren -UNI-DIN -Other
The best analysis (I'm sure most folks are aware of it already) is Graeme Dennes' two papers: a)
An Analysis of Six Major Articles on Tonearm Alignment and Optimisation; b)
Is the Lofgren 'A' Solution Unique? I found them for download at the
vinylengine dot com site.
Dennes' survey shows that Erik Lofgren was the first to solve the geometric problem of minimizing lateral error (WTE, or weighted tracking error). Baerwald, Seagrave, Stevenson, Kessler and Pisha also produced optimum solutions, their equations identical to Lofgren's, with some different notation.
In addition to his primary solution, Lofgren developed an alignment to minimize WTE in arms where the offset angle was fixed (as I understand it, the cartridge could not be rotated in the arm to provide an optimum angle), but overhang could be adjusted. This 'solution' was obviously a kludge, and can be discounted. No one should be using such a tonearm, today.
Lofgren also devised a third alignment which solves a different problem than minimizing WTE. This alignment minimizes a possible psycho-acoustic effect. That is, a so-called 'cumulative annoyance factor'. The alignment lowers WTE peak distortion between the nulls, at the expense of increasing WTE at the inner and outer grooves. Thus, this alignment can be said to solve a different problem than that of minimizing WTE, but is certainly a valid approach.
In addition to confirming Lofgren's WTE solution, Stevenson also devised an alignment for specifically reducing inner groove distortion, at the expense of higher WTE distortion over the rest (around 75%) of the record. This alignment was devised primarily due to poor tracking from cartridges and arms in the '50s and '60s. With modern stylus shapes and better arms, it is mostly a solution to a problem that no longer exists. I have read that this is the alignment Technics uses for their turntables (the little white plastic jig everyone is familiar with). If it is so, perhaps in a disco, inner groove distortion is a bigger factor than would be the case in an audiophile environment, and that could be the reason for it. If there is a reason.
Of academic/forensic interest is the fact that Baerwald was familiar with Lofgren's paper, but did not give him credit for it, at a time when others did not know of this earlier work. To quote Dennes:
However, a further injustice was done to Lofgren. To the best of the writer's knowledge, Baerwald never refuted the ongoing professional recognition accorded to him by peers and the audio world for the development of the optimum alignment solution, He again chose to remain silent.
To wrap, Dennes also discusses the even earlier, but incomplete work of Bela Harsanyi and Percy Wilson.
