Discuss The Viv Lab Rigid Arm

@intactaudio Dave good to see the inquisitiveness ( the quality of wanting to discover as much as you can about things), is proving to be availing.

I was off this thread, but my visit and your last post has got me 'back in the game'.

As said, I have been fortunate in having it agreed a New Tonearm Design, I am being asked to be present for a demonstration and offer a assessment of the demonstration experience, has been agreed to have one of the models set up as a Underhung Geometry.

It will be a rigidly coupled Mounting, it will be used in comparison to the 9" and 12" Overhung Geometry. The length of the Arm to be allocated for a Underhung Geometry is yet to be made known.

The Plinth/Chassis will be able to mount Two Tonearms to a 12" length.

The demonstration is to use a Two Cart's, same Brand/Model with very similar hours of usage.

The Tonearm Design also has a Geometry, that has the Styli when in the Groove at the same height as the Vertical Bearings Axis Pivot Point.

Your taking the time to create the experience and evaluate, has been a added boost to my intentions. I am keen to see what is able to be created and where the attraction of the Geometry can be discovered, in relation to the Overhung alternative.

As per usual, whether Overhung or Underhung, all assessments will end up as a subjective evaluation, that is to be made through drawing from multiple years of experiences of being demonstrated multiple differing HiFi related Designs being put to use. 

There is a Computer Programme available occasionally for System Health Checks, especially for a Vinyl Set Up. The use of this on a well known system produced a end result, where the improvement in the presentation was by myself perceived as almost Tangible. The imaging become very focused and the performers were more present than what was remembered. This Software might? be available for the demonstration day as well. 

It will be used at some point to give the New Tonearm Design the fairest of lore, as getting the Cart' optimised in its set up Geometry will go a long way to help learn as much as can be offered.

Pindac, I’m sure you know this, but because you did not mention it, I hope your underhung tonearm will be built with zero headshell offset angle.

Dave, in your aural experience reported above were you listening to an RS-A1, or what? Also, what is “arbitrary distortion”? Could it also be called “subjective distortion “? Thx.

@lewm, "nothing" is the ideal goal. The tonearm's job is to hold the cartridge rigidly in the right position to do it's job having only two degrees of motion, vertical and horizontal. The right position is tangent to the groove with a SRA of 92 degrees and a stylus azimuth perfectly perpendicular to the surface of the record. The tonearm can not resonate in any way and should have frictionless bearings. 

There is no perfect tonearm, but in evaluating tonearm designs I think it is helpful to keep this in mind and make as little compromise as you can, picking the compromises that are least harmful. When you add into it that you are dealing with a sprung suspension and an unavoidable resonance problem the cartridge itself becomes an important factor in the design of every tonearm and has to be kept in mind. 

So, there is this push-pull situation in tonearm design. Fixing one problem makes other problems worse. I believe, since there is always a threshold under which problematic issues become inaudible, the appropriate approach is to minimize all the problems in a balanced fashion and hopefully bring all of them in below the threshold of audibility.  Many very smart engineers have looked at this problem and the vast majority of them have decided that the 9", pivoted, offset tonearm does this best. Newer tonearm designs utilizing the Thales algorithm like the Schroder LT and the Reed 5A and 5T may advance tonearm design to the next level. The principle makes enough sense that I would be willing to try it. Carriage driven tangential tonearms also make sense but are much more complicated and expensive to make. I put air bearing arms and this Viv arm in the same category, arms that optimize one or several factors at the gross expense of another which I find unacceptable. Maybe the distortion caused by this is inaudible to some people, but it is there and is audible to some of us.  

Lew, if you look at the business end of the Schroder arms he uses the same design on all of them, a cartridge mounting plate is attached to the end of the arm with one screw in a slot. So the cartridge can be twisted within a certain range and the overhang can be adjusted withing the range of the slot. If you mount the cartridge with only the inboard screw you can twist it straight and slide it back creating an underhung arm without any offset. This may not work with all cartridges but it does with the MC Diamond because I tried it. This configuration definitely caused enough havoc with imaging that I am pretty sure I could pick it out reliably in a blinded AB situation. 

@intactaudio , it is always safe to assume the math is always right especially when it comes to human hearing. Just because some obviously defective designs sound OK to some people does not make them any less defective. It is an interesting but extremely complicated and hard to fathom, not tonearm design but the psychology behind human hearing. I think it is analogous to the Rorschach test. Show 10 people an ink blot and you will get ten usually different impressions of what the ink blot looks like. The same is true of sound. It depends on that person's experience, preferences and state of mind.  

Math without an attachment to a subjective listening experience is only worth the computer screen it is displayed on.  Your Rorschach reference is a perfect one for this situation and you seem to be the therapist explaining to the patent what they should be seeing based on some measured metric.

dave