Creative and cheap DIY turntable/tonearm tweaks

Jyprez, you're correct in your description of compliance, and all would be exactly as you describe if the record was not turning. As soon as the record starts turning it is not perfectly flat and the cartridge is deflected up and down by small amounts all the time. This is where mass becomes very important, since the higher the mass the higher the inertia to the deflections. If the cartridge compliance is designed to be able to withstand the deflections of a low inertia tonearm it will not work at all well when you add sand and massively increase that inertia.

At best you'll change the resonant frequency of the tonearm - cartridge combo, almost certainly to the detriment of the sound quality. At worst you'll ruin the LP, the cartridge, and possibly even the tonearm bearings.

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.