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How to measure tonearm effective mass

Some of us who use high or low compliance cartridges fret about mating them with tonearms of low or high effective mass, respectively. Most of us rely upon data supplied by some manufacturers to specify the effective mass of their tonearms, but many manufacturers do not even supply such data. Does anyone know a simple and relatively accurate method for determining effective mass? We know what "effective mass" is; we want to know how to measure it.
lewm
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czbbcl
1,699 posts
 
Lewm

Aren't you glad you asked ........

Chuck
lewm OP
6,770 posts
 
Chuck, I AM glad that the question brought responses from some of the most knowledgeable people around this part of the hobby.
Viridian, The Catch-22 is the bit about needing a cartridge of "known" compliance. I guess one can figure that out by starting with another tonearm of "known" effective mass, or else one can start with manufacturer data, which I am not at all sure I trust. But thanks. As far as that goes, there was a neat idea from John Ellison on VA that is germaine to this issue. For a case where we know either the effective mass or the compliance of the cartridge, you simply drop the stylus onto an LP whilst recording the harmonic motion of the bouncing cantilever. For that he uses his computer and appropriate software. Once you freeze the decaying sine wave that describes the signal coming from the bouncing of the cantilever, you can make measurements that will get you back to the unknown parameter.
Mark, Did you make reference to the John Ellison method? I will take a look.
lewm OP
6,770 posts
 
Mark, I see you had posted your own novel method on VA. Looks a bit cheaper to try, compared to John's which requires one to buy the requisite computer software. Thanks.
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czbbcl
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Lewm

I was just being facetious ... You ask a simple question and get very complicated answers but you are right it is a very good question...
lewm OP
6,770 posts
 
Hey Chuck. Are you THE Chuck, formerly of Northern Virginia, to whom I spoke at RMAF?

The confounding reports of apparent tonearm/cartridge mismatches that sound great have me thinking about the quality of the data for compliance and tonearm effective mass that we start with. Also, for some of the newer/newest tonearms, there are NO data coming from the maker. To wit, I asked a dealer about the effective mass of the Talea. Turns out an exact number is not available.

Of course also, Raul and others have correctly (probably) pointed out that the compliance/mass issue is not at all the sole determinant of a good tonearm/cartridge marriage. I suspect that is a very important truth.
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