Cartridge Loading and Compliance Laws

Tony,
I accept your analogy with respect to record warps. I was more referring to the stylus/arm relationship in the normal condition of tracing a flat record groove.

Lewn,
What I meant is that the tonearm is not moving in relation to itself, while a car or truck is moving, thereby creating what I referred to as momentum inertia. You know, an object in motion tends to stay in motion. Knocking a moving vehicle off its line requires a force that increases with the speed of the vehicle. You dont have that issue with a tonearm, which is relatively fixed as compared to theh speed of the record groove. Sure, it has to travel across the record, and up and down over warps, but not at anything close to the speed of the wiggles in the groove, which at the outer groove is traveling around 1.74 ft per second. A 20 minute record requires the arm to move horizontally about .001375 ft/sec assuming a 4" playing surface. Hardly a meaningful comparison. That makes me believe that holding the cartridge steady and just allowing the stylus to move is the more accurate method. Again, I am not addressing warps. I do see, however, that once the arm does move, a heavier arm will tend to overshoot and be slower to react and return to the neutral position.

Doesnt the Townshend fluid damper trough at the headshell end essentially create a condition that the stylus would see as a more massive tonearm. I can tell you from experience that the Townshend system works very well, and cleans up the bass tremendously as compared to the same cartridge/tonearm without the damping trough.

Dear Manitunc, My point is that you cannot make the general statement that a heavy tonearm is "better" than a light one, or vice versa, because there are other factors involved and for sure there are conditions within which either proposition is the correct one. And the model of a cartridge held static in space is a bad one to start from, I still say.

"An object in motion tends to stay in motion". Yes, that is inertia.
"Momentum" is a quantity applicable to a body in motion. Momentum is equal to mass X velocity. Inertia also says that a body at rest will tend to stay at rest. A body at rest has no momentum.

This comment really makes me think, as I had no idea.

"Increasing the counterweight mass and then moving it closer to the pivot in order to maintain the same VTF will reduce the eff mass."

This could really help someone I think, in some cases at least. I wonder though how to judge how much the eff mass is reduced when the heavier weight is added and slid forward...would this be figured by somehow reducing or subtracting the actual amount of weight added to the counterweight to begin with from the starting eff mass without the extra weight??

I wasnt making a general statement that a heavy arm is better. I was just trying to think through the variables and it seemed that a heavier arm would do the things an arm is supposed to do better than a lighter arm. I dont know if that is true, however, since I havent been able to hear and compare the universe of arms out there. My thoughts were just that I seem to hear a mantra of heavy arm = low compliance cartridge, light arm = high compliance cartridge and was questioning whether that is true. Again, I dont know and only seek to understand and learn.

"heavy arm = low compliance cartridge, light arm = high compliance cartridge"
Yes, that is a mantra of the internet that I read very often, too. As I am sure you know, that formula is meant to set the low frequency resonance at a frequency between 8 Hz (so as not to excite resonance via footfalls and other very low frequency sources) and 12 Hz (so as to stay away from the audio bandwidth). The formula for that resonant frequency can be found on Vinyl Asylum and in other places, but tonearm effective mass and cartridge compliance are its principle determinants. So this is why the gurus tell us, "heavy arm = low compliance, etc". However, there are guys on this discussion group, most notably Raul, who point out that there are many other factors that determine the overall "goodness" of a match between tonearm and cartridge and that sometimes one can and should overlook the mantra in search of good sound. One example is that several owners of the Fidelity Research FR66, a 12-inch arm with very very high effective mass, claim it sounds fantastic with MM and MI cartridges that have very high compliance. Conversely, some others who own very light tonearms like the ADC and the Black Widow like to use them with MC cartridges that have low compliance. To all this I say, "go figure". The take home lesson I think is if you have a tonearm you like a lot, don't stop using it just because it might technically be a mismatch with your new cartridge, on the basis of its effective mass vs the cartridge compliance. All bets are off.

Why this is true is worthy of another separate discussion, but I have my ideas.