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JMW 9 effective mass?

I read on vinyl engine that the effective mass of the JMW 9 is 7.7 grams. If this is true, that would make the JMW 9 a LOW MASS arm. My cartridge is supposed to be used with Moderate to High mass arms. Its compliance is 15. I think I have a mismatch. Why doesn't VPI publish this information so I would not spend $1,500.00 on a cartridge that sounds wrong on my table. I have a Benz H2.

I was told that my arm is in fact a moderate mass arm. Well, where are the specs indicating this? I want to see for myself. If I have a low mass arm, I should be using high compliance cartridges, correct?

Where do I get this information, it did not come with my tonearm, it just had information on installation

What is a good High compliance cartridge?
tzh21y

Showing 3 responses by cmalak

cmalak
681 posts
 
Tzh2ly...you should call VPI and ask for the effective mass of your tonearm. There is a bit of confusion on this because VPI has had variants of the JMW9 and JMW10.5i tonearms depending on the material used in the armwand (aluminum vs stainless steel). I believe the 7.7 grams effective mass for the JMW9 measurement is for the aluminum wand. You should get the effective mass of your specific tonearm and then just use the calculator on this page (Freek's Resonant Frequency Calculator) for tonearm-cartridge matching: http://www.theanalogdept.com/cartridge___arm_matching.htm

What is the weight of the Benz H2 cartridge?
cmalak
681 posts
 
Tzh21y...do you know how much your Benz cart weighs?
cmalak
681 posts
 
If the JMW 9 tonearm is indeed 7.7 grams effective mass and the Benz cart's weight is 9 grams and compliance is 15, then the calculated resonant frequency is 10Hz, which is exactly where you want it to be (acceptable range is 8 - 12 Hz). If the JMW 9 tonearm effective mass is closer to 9 grams (as per your discussion with Harry), then the resonant frequency with your Benz cart is 9.7Hz, so either way, your Benz cart should be a good fit. Hope this helps.
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