Special Announcement: Abis tonearms will be sold under a new name, Sorane. The production and design are exactly the same, being produced in the same facility. The ownership of the design has reverted to the OEM. Please click HERE to be redirected to the Sorane page.
Abis SA1-2 Geometry
One thing not always stated in tonearm literature is whether the tonearm in question uses the Stevenson, Baerwald or Lofgren geometries. In many cases, older arms adhered to the Stevenson standard. The theory behind the Stevenson alignment is that it lowers distortion on the inner grooves, which are often the most challenging when playing symphonies/operas/soundtracks etc.. Since then, there was a sea change. Pop and rock outsell classical several hundred to one. In light of current trends, the Baerwald geometry works better for many pop disks, which tend to have high levels of modulation in varying areas (at the discretion of the producer and group, the loudest track could be anywhere on a disk).
Since there is no correct answer to this question of geometry, the Abis SA1-2 geometry was chosen to fall at a point between Stevenson and Baerwald (Lofgren A). You can adjust the overhang to make the arm perform more like the Baerwald (Lofgren A) or Stevenson geometries, if you desire (see below). Here are the results using the supplied protractor, assuming the spindle-to-pivot distance is correct:
Here are the actual projected distortion levels:
This shows that the SA1.2 is comparable to the standard curves. It does, however, require the Arc Protractor to get the lowest possible distortion from the arm, and actually line up to the custom geometry chosen by Abis.
One other thing should be noted. By slightly changing the overhang of the cartridge, the geometry can be made more like Stevenson or Baerwald (Lofgren A). I experimented with minor changes in overhang and came up with some interesting results.
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An important thing to remember is that unless your arm exactly matches the geometry of a given generic protractor, the generic protractor might cause noticeably higher distortion. Generic protractors can use any popular alignment, or even use a custom alignment. You should know if your arm is compatible. If you go to Vinyl Engine and input your tonearm’s specifications, and they do not exactly match Stevenson or Baerwald, and you don’t have a factory supplied protractor, you should have a custom arc protractor made. This is why I supply the Accutrak Protractor with Abis tonearms.
[gview file=”https://mockingbirddistribution.com/wp-content/uploads/2015/09/Abis-Accutrak.pdf”]