Dear Geoch, tonearm geometry and thus optimized alignment is indeed predictable. The mere geometrical parameters of a given tonearm do show which calculation curve is suited best to its inherent design.
However - I do not want to stress that point, but I need to mention again - it does play an important role too, whether the majority of one's records is rather older vintage and more cut following DIN or whether your platter is only spinning reissues of the 1990ies and our day ( which are indeed all following IEC standard).
Tonearm geometry is one of the few truly predictable areas of audio.
But it needs attention to detail and taking into consideration all aspects.
In the past 2 decades tonearm geometry was sadly neglected by many - in the awareness of most people we had Baerwald IEC and that's it.
Few did question why there still were other calculations and why certain tonearms did sound fabulous in one system set-up and were trashed aside by other audiophiles as mediocre at best.
To address your question of a few posts before: If the line of your aligned cantilever is off-line compared to the offset angle ( i.e. they do NOT share the same angle compared to your tonearms main) of your tonearm (or a fixed offset angle in a fixed headshell ( SME V for instance )) then you have another - an additional - breakdown torque moment in the static force model of your tonearm.
Now what does this mean in plain words and practical sonic results ?
In most cases it will result in an increased skating force - resulting in higher unlinear distortion figures.
Now why "specific" templates for specific tonearms when Löfgren, Baerwald or (sometimes ..) Stevenson would satisfy all our needs ?
Because some tonearm geometries are VERY strange (read: sub-optimal .. . for instance the SAEC 506/30 which geometry is optimized to track 10" records !) and some are just a way off and can be MUCH improved with small alternations to the designs geometric parameters ( my "beloved" FR-64s for instance...).
As said before - Raul and I are in agreement on most of these topics. But IMHO and following my personal experience I believe that there are some designs out there which call for a bit more attention to detail and which can not be optimized "following the books".
Sometimes I might be a bit too obsessed with attention to detail and questioning undisputed "facts", but IMHO tonearm alignment and geometry are fields of plain and rather simple physics and need only attention and precision to pay off their "sonic" fruits for all of us.
Cheers,
D.
