Creative and cheap DIY turntable/tonearm tweaks

Ah, Ok so you are (both) saying that the cantilever needs to move in the vertical plane as well as horizontal for music reproduction (or is it just because the record is imperfect and potentially warped?)? I had thought that stereo reproduction only depended on horizontal movement and that the record grooves were flat in the vertical plane (except for that expirement back in the 70's with Quadraphonic). Certainly you are right that if a cantilever must go up and down in response to the grooves, more mass would be damaging to the record. If, however, it only moves horizontally, more mass (not more weight, just mass) would not damage the grooves.

Since the groove walls are angled, there is inevitably some stylus movement in the vertical plane. But there are very big vertical movements when a warp in the record is encountered. A large mass will actually leave contact with the record after being "thrown" up in the air by the warp. Then it will come back down at some later point of the record. This is generally not desireable. Typically, designers will make the arm as light-mass in the vertical plane as is practical. This normally also sacrifices horizontal mass, and was the reason for my tonearm mod, which separates and allows different mass in the horizontal and vertical planes. When an arm is not designed to have independent vertical and horizontal masses, then there is an inevitable compromise between light vertical mass for warp tracking, and heavier horizontal mass for cartridge stability. One or the other will suffer from the compromise. I promise that I did my homework.

Jyprez ... you're right ... if it only EVER moved horizontally there would be no problem. But that is never the case, even if the record is not warped. There may not be large vertical deflections, but there are small deflections on all records (at least all that I have).

BTW Twl is way ahead of me on turntable knowledge, but I did recently read an interesting web page on compliance, tonearm mass etc etc ..

http://www.gcaudio.com/Archives/tonearmcartidge.htm

TWL, If there is a large horizontal oscillation, as happens if the cutting path spiral is eccentric, then the large horizontal mass, as you describe it, works against the stability of the cartridge stylus pressure and skating.
BTW, I think that the term with which you have been struggling to describe the principle of "horizontal" and "vertical" mass, is Polar Moment of Inertia in whatever plane that you want, horizontal & vertical.
I have no doubt that you did your homework on this and am contemplating making the same modes to my Rega 300 on the Alex IV. I do have some (2 or 3) quite eccentric LPs and it might be interesting to see if the increased horizontal polar moment will resonate with the frequency of the eccentricity.

Salut, Bob P.

salut, Bob P.

Bob, I believe the mod as I applied it is forgiving of the larger movements of record eccentricities. And it seems to have no effect on the slow tracking of the spiral groove as it traverses the record. I have no "wildly" eccentric records in my collection, so I don't know if this will be a problem for the arm with my mod, but I am considering the effectiveness on a "normal" LP to be of greater importance than its performance on a "defective" LP.
Yes, I'm aware of the Polar Moment of Inertia, thanks for reminding me.
I'd like to hear what results you get, especially on the really badly eccentric records.
I'd also like to remind you that the benefits of this mod will become smaller in effect with higher compliance cartridges, and will be of no use at all with very high compliance cartridges. I have tested cartridges up to 15cu with Rega arms, and they are still getting benefits from this mod. How much higher in compliance you can go, without losing effectiveness entirely, is unknown to me at this time. I would say, though, that any cartridge that would normally be considered a good resonance match with a Rega arm, would receive some benefits.