Creative and cheap DIY turntable/tonearm tweaks

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.

TWL, upon rethinking my concern for horizontal resonance at the frequency of eccentricity, that shouldn't be a problem, as the frquency will be either about .5Hz or 1Hz and the mass would really have to be high for that to occur. Also, I should have mentioned that my cartridge is a BPS.