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Calculation of effective mass of JMW10 tonearm?

Does anyone know how to calculate the "effective mass" of the JMW10 tonearm? Or better yet, can someone just tell me the number in grams? I am reading "How to Set Up and Tune Your Turntable and Tonearm" by George Merrill. In the booklet he recommends a tonearm resonance frequency between 8 and 16 Hz, 11 being ideal. I have already been told my just purchased ZYX R100FS (Fuji Silver high output) is a good match for the tonearm. But in trying to optimize the sound I need to know the tonearm resonance frequency which requires knowing the effective mass of the tonearm.

Help please. Thanks,
Jon
jonathanochi
dougdeacon
3,338 posts
 
Kehut nailed it.

I haven't used a ZYX on a JMW, but VPI/Mike's suggestion to use both their 3g headshell weight and a lighter c/w mounted further aft sounds right to me. I have this vague recollection that the eff. mass of a JMW-10 is around 11g. If that's so then Mike's advice is spot on.

If you want to measure your resonance frequency, the HFN&RR test record has tracks specifically for that purpose. You'll be able to confirm resonance in both vertical and lateral modes to the nearest 1 Hz or so. A ZYX has different vertical and lateral compliance, so the resonance frequency will be slightly different in each mode.
brrgrr
163 posts
 
Jon, I have a Yatra cartridge, and spoke to mike just a wweek ago about the same situation. He is sending me both the headshell weight and lightweight drop counterweight, for $60, and his recommendation was exactly as Kehut stated.
I'm sure he'll do the same for you, just contact him .Very pleasent guy to deal with.
Carl
jonathanochi OP
20 posts
 
Sorry to be slow in thanking everyone for their suggestions. My computer network was down. I got way behind on everything.

I did contact Mike at VPI, John and Ken. That was a good suggestion. Doug, your memory of the effective mass of a JMW 10 at around 11 was very close. Mike says it is 10.3 grams. And, Carl, I ordered and then set up my arm with the lightweight dropped counterweight and the headshell weight. Although when I weighed mine it came in at just shy of 5 grams instead of 3 grams.

In any case, the JMW 10 with the ZYX R100FS (silver Fuji) sounds fabulous. It is so very quiet and clean. I am very, very pleased.

Jon
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