I like to think Sparky and I are colleagues and on friendly terms if not too presumptuous, friends, and he has been a good mentor in many ways. That said, he is correct that the earlier Southers were imperfect works-in-progress that Lou never really completed while his project. Mine is an earlier version that has been a bit of a science fair project. Lou addressed many of the problems in his way, me in mine. The one change he made I never liked was going from the hollow arm stick to solid, the hollow stainless-steel tube allowed filling with a particulated damping medium which was a definite improvement. His improvements increased rigidity of the gantry frame, arm stick, and the rail plate, probably raising their resonance freqs, while mine dealt with the resonances with dead-mass load damping in 3 critical areas, the gantry frame, the arm stick, and the rail plate. The dust cover must come off and the wire guide rod and cueing shaft be damped via wedging felt pad dampers. I probably should have asked him for a Tri-Quartz rail plate to try but it never occurred to me to do so when I had the opportunity. The resonances are apparent to some immediately, to everyone by their absence when dealt with. The resonance management benefits include less 'peaky' more neutral tonal response, tighter image focus & better 'staging', and cleaner more precise micro-detailing and micro-dynamics. The mod'ed assembly exhibits (IMHO) a uniquely remarkable and absolutely captivating ethereal precision of reproduction.
I have yet to try the single-run signal lead mod but perhaps someday when I have satisfied myself that the fundamental problems have been addressed (and I may be 'there' now).
FWIW, some are concerned about the air bearing arm air cushion decoupling effect affecting sonix and I believe Bo Hansson of Opus-3 recording/ Rauna was one such. He was the Souther agent for Sweden and instituted his own improvement program which, with Lou's blessing AFAIK, resulted in the similarly as-yet incompletely perfected but elegantly simple Cantus cantilevered gantry LT arm, see attachment. Like Lou, Bo spent a lot of time listening to variations of material and components in development to make what they thought the best sounding choices for the final product. Bo passed a year and a half ago and so with production now in limbo, his partner intends to perfect and stabilize the design of the Cantus and bring it forth again. As nice as the produced ones looked they were more proof-of-principle variable-example items that could be more a daunting "science fair project" for the user than a finished product as ergos and ease-of-set-up went. Mounting & VTA and levelling set-up difficulties and the fact that they don't swing out of the way, up like the Souther or 'garden-gate' style like the Linatrack gantry are but some issues to be addressed. There is a very long and interesting thread on this thing in DIY audio;
http://www.diyaudio.com/forums/analogue-source/34126-opus-3-cantus-parallel-tracking-arm.html
The Clearaudio LT arms are pretty much "perfected" as far as finish, construction, and ergonomics are concerned and use principles of either the Souther or Cantus depending on which model/version. Bo thought the thin tube arms the best approach as did Lou and it appears that Clearaudio chose to abandon that concept for thicker arms. Otherwise I actually in theory and practice prefer the secure 3-point mounting of the earlier Souther gantry frames with the spindle locator rather than the cantilevered later versions tho' have not auditioned them.
