general tonearm design question


Many popular tonearms are designed with with the fulcrum for the vertical axis at ~70 degrees (e.g. Rega, SME), rather than perpendicular (e.g Origin Live).

Doesn't the former design cause the needle to track to the outer groove as the counter weight swings downward?

...or does the cartidge/tube somehow counter this?

Would a counter weight mounted at 90 degrees to the fulcrum, yet the arm tube set at 70 degrees be the solution to this, or am I wrong?

(The reason I started wondering about this was due to the varous Rega counter-weight mods. I would think that a lower center of gravity would exacerbate this problem. Furthermore, wouldn't a lower center of gravity only be effective on a uni-pivot design?)

your thoughts?
128x128popluhv
Don't worry,Doug.No problemo.Feel free to mention the 2.2,it really would be silly for me,or anyone to get offended by a product comment.So long as the product sounds good,I don't care.The past is an embarrassment to me,so don't sweat whatever you feel like saying,at any time!!
My friend just got the Phantom,and it is superb.Being that we both have "flat platters",at all times,due to vacuum,the issue of the "true" unipivot 2.2 does not seem to be a big deal to me.I never see any twisting movement of sideweights when playing LP's.Yet,I think the Phantom is fabulous.It has it's own idiosyncrocies though!
BTW,yes,the Triplanar is not so bad either.-:)
Best!
Doug. Are you saying the azimuth on a uni changes each time you adjust the VTA? Wouldn’t a unipivot simply keep a consistent azimuth over an elevation on the record? I cannot recollect that I have ever had to adjust azimuth after I adjusted the VTA on any of my unipivots, and I frequently play with VTA adjustments (almost on every record).

Regards
Paul
Doug. Are you saying the azimuth on a uni changes each time you adjust the VTA?
No Pauly, I didn't mean to imply that at all. Sorry if it came through that way.

I was suggesting that IF an unstabilized unipivot relies on stylus/groovewall and cantilever/suspension pressures to help maintain steady azimuth, then:

a) this could make it more difficult for the stylus/cantilever to respond freely to subtle groove modulations and;

b) this would tend to make for constantly changing azimuth on WARPED records. If azimuth depends on the angle of the groove walls, and if that angle changes due to a warp, then... obvious conclusion.

Point (b) is virtually insignificant IMO. An arm with fixed bearings will maintain stable azimuth relative to the platter, but if the record is warped the azimuth relationship of stylus to groove will change because the groove is changing. I only mentioned it to counter the (silly) argument that someone once offered that a unipivot could compensate for warps by changing azimuth in real time.

Of course we should all have SirSpeedy's vacuum platter. Then point (b) would be non-existent!
Doug,I honestly don't know of "any" unipivot that relies on stylus/groovewall and cantilever/suspension pressure to help maintain steady azimuth,or balancing.That,alone,would be poor design,and would surely put a "TON" of pressure on the stylus/suspension.Who knows?Maybe I have more to learn,but I don't think my arm,or my friend's VPI rely on this.
They sure sound good though! -:)
BTW,without you knowing it,I am reporting that your EP-15a listing(Nsgarsh too) aided me in getting one!I included the Exact Power Ultra-Pure to go fully balanced.THIS combo is the the biggest improvement I have made to my system in a long while!Stuff like vta/azimuth/downforce changes are WAY more obvious with super clean A/C,and I'll bet many folks don't know how much more can be had!
Best regards!