Regards, Halcro: A question from analog hell, Devil Henry!
Let's proceed from the premise that response is the sum of mechanical and electrical properties. With an electro-magnetic generator current is proportionate to stimulus, in this case provided by groove modulation, and, that the frequency of a recorded signal is inversely proportionate to its length along the groove.
Response limits are reached when a state of excessive electromotive force exists, resulting in saturation of the coils in which condition current actually decreases. Or, when due to either extreme acceleration or magnitude of groove modulation the stylus is no longer able to track accurately. The consequence is either distortion or damage to the groove walls.
A 1kHz signal recorded to vinyl represents a displacement of 80 microns and at 20 dBl a peak acceleration (according to a study by St. Andrews College) of 3km/s/s, "the equivlent of acceleration 320 times that of the earth's gravity". These forces are exerted on the stylus which in turn drives the cantilever (we're moving right along here) ;)
View the cantilever variously as a rod, tube or beam, it will none-the-less tend to resonate at certain frequencies. A cartridge's suspension functions as both a bearing and damping mechanism, the lower the compliance the greater the damping properties, a constrained beam is less prone to sustain vibration. The down side of this is if the cantilever is overly damped it tends to flex and scope of excursion is diminished. If compliance is too little, damping factors are reduced and cantilever recovery times are reduced. Neither of these conditions are a particularly good thing.
Let's consider the cartridge suspension as both a spring and dynamic vibration absorber. Cool, but it takes a tonearm to make it all come together and the damm thing has mass which must be accounted for. All the above conditions tell me so.
In a paper presented to the AES, Shure technician C. A. Anderson states:
"resonance exists because the arm and pickup assembly behaves like an effective mass that is coupled to the record groove by means of a stylus assembly with its own mass, compliance, and mechanical resistance". Sounds like a team?
Ideally, frequencies below the natural resonance produced by warps, eccentric groves or surface imperfections will not disturb the signal because the tonearm and cartridge move as a unit. This occurs when compliance and mass allow the tonearm and cartridge to remain centered above the groove. Modulations are read by the stylus (tracing), the stylus reads both sides of the grove equally (tracking). When cartridge and tonearm remain centered, the assembly floats with surface anomalies and the signal is unaffected.
Resonances can be considered as being constructive or destructive. When a recorded signal matches the natural resonance of our tonearm/cartridge, Mr. Anderson states the recorded signal can be enhanced by 6 to 20 dBl. He doesn't state such but in the instance of destructive resonances a diminution of signal at specific frequencies might be anticipated. Under certain system related conditions this may (or may not) be heard as beneficial.
At resonant frequencies the stylus tends to "scrub" in the groove, in the instance of a gross compliance/mass mismatch the entire tonearm can be seem moving laterally. Wow, flutter and warbling might be observed. This is because as the stylus scrubs in the groove it describes an arc, effectively adding or subtracting from desired groove speed. Floor and air-borne vibrations also tend to excite resonances in a tonearm, this due to cantilever resonance, damping inadequacies (of some description) and consequently a complimentary spring/mass relationship become a consideration.
Passive damping techniques such as isolators, vibration absorbing materials or viscous dampers, active damping mechanisms incorporated through electronic means, or simply ensuring an optimal compliance/mass ratio exists are means of addressing these unwanted resonances.
Hope this answers your question regarding the desirability of matching compliance/arm eff. mass?
Peace,
