I was originally taken in by the title of this thread, i.e., the old MM/MC argument. But what I find more interesting is the discussion that centers on how to determine Effective Tip mass or ETM. If I understand correctly,
@thewas you advocate the direct method which is by dissecting the actual individual parts and summing their contributions, and
@JP you advocate the indirect method which is by measuring the resonance “due to the ETM against the compliance of the vinyl”. I think both of you are correct, and I will explain. Please allow me to preface with a heuristic example.
Let’s say we have two identical stylus assemblies – same magnets (MM) or same coils (MC), same cantilevers, same suspensions, same damping, and (important!)
identical mass diamonds that are mounted the same way. The only difference between the two is that one diamond is conical and the other diamond is some micro-line cut that has a greater contact surface area than the conical. OK so far?
By using the direct method, both assemblies would have the same ETM as measured and calculated in a lab.
By using the indirect method, the larger contact area of the micro-line stylus assembly would be expected to yield a mass-to-vinyl-compliance resonance frequency that is
higher than with the conical. This would infer that the micro-line assembly has an ETM that is
lower than the conical assembly, but we know from the direct method that it does not.
Being a retired engineer, I intuitively feel better with the direct method. The outcome is clear. A directly determined ETM number can stand on its own, and can be verified by an independent third party lab. Trouble is, I suspect that the instrumentation and expertise needed to directly measure the actual individual tiny parts of a stylus assembly is few and far between.
On the other hand, I feel persuaded that the
result from the indirect method is more useful, practical, and more accessible to the average experimenter. But this can only true if a
standardized test record is used. The formulation of the test record vinyl, the elasticity, damping characteristics, etc., etc., can affect the outcome. A standardized test record would ideally control all those variables. The indirect method might yield a useful number, but it’s not necessarily a true indication of the actual ETM. An analogy might be the difference between your local weatherman announcing the
actual temperature on the thermometer and then announcing what the “feels like” temperature is, which factors in humidity and moisture evaporation on your skin.
IMO, it would be helpful to adopt a new initialism for indirect method “ETM”. Instead of “ETM”, how about calling it Effective Tip Mass Frequency or “ETMF”, or something else. It might even make sense to make it a unitless value. This of course only relates to resonance “due to the ETM against the compliance of the vinyl”, which I take it is desirable to be above 20K. In the 1978 Audio article Shure engineers relate ETM and ability to maintain groove contact (trackability) at various stylus velocities, and factoring in groove modulation amplitude within the audio frequency range.
Ray K