T Bone
I take on board all your points, and, as it happens, I agree with Dertonarm on some points. I just wish he would stop obfuscating and avoiding admitting he has completely missed the point on others.
Regarding reasons for different weighting, check out Keith Howard's piece in the features/reference section
http://www.stereophile.com
You said you couldn't get the numbers to match and something had to give. Something always does. In this case, the theoretical world. I never saw the point of giving numbers which were impractical for set up. Thirty years ago, no one set their tracking angle and the rest, to three decimals.No one does today. The numbers were rounded up for a nominal effective length of 230. The important word is "nominal". I should have perhaps laboured the point more, but that was back when tonearm geometry was perhaps better understood, and the issues concerning the choice of design - sliding vs fixed pivot, slots versus holes etc, were better appreciated.
How are you doing with the SME (or rather, sliding base) geometry? I'm going to post an explanation separately.
You said
Your point about 'just adjust angle and mounting distance as necessary' is EXACTLY right and appropriate given the imperfections we each bring to the table when we mount a tonearm/cart, but that is the art, not the science (and most of the critiques of Dertonarm's ideas and protractor on this thread are on the science, not the art, of tonearm setup, and his product I would think is specifically addressing ease of getting the art right - because the science is gotten right by anyone who gets the algebra right).
If his device makes setting up easier I'm all for it, but not if it is less accurate.
That was my reason for posting originally. He doesn't say what the accuracy of his device is, compared, for example, to a paper two point. Now I don't know how accurate a paper two point is, but I do know it is more accurate than the easier one point - two nulls are always better than one, as they allow an obvious a way of double checking. And in any case, as Dertonarm has said in the past:
But the alignment of the zero (points) is the raw basic on which everything else builds.
So, adding an arc in addition should certainly make it easier to set up (for a specific effective length) as the arc and the nulls must intersect, thus giving two opportunities to check offset.
I don't have a problem with that, I think it is a good idea.
If it is easier, great, fine, but is it more accurate...?
Hopefully, if not DerT, then someone will tell us.
J
