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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
tzh21y OP
1,654 posts
 
VPI (I believe it was Harry) did tell me that it is a low mass arm somewhere around 9 grams and recommended a headshell weight. He said 3 or 4 grams should be sufficient. I guess Elusive disc has them. He said the difference will be very noticible. I shall find out. The compliance of the Benz is 15 and is recommended for medium to high mass arms.

He also told me to heat the cartridge with a lamp or blowdryer prior to listening. That is what he does with his Benz. I knew there was something that just was not right.
cmalak
681 posts
 
Tzh21y...do you know how much your Benz cart weighs?
tzh21y OP
1,654 posts
 
9 grams
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.
tzh21y OP
1,654 posts
 
On the cartridge specifications, it says for best performance, it should be used with a medium mass or high mass arm. I have read that anything below 12 grams is low mass which is what the JMW 9 is. So it should be mated with a higher compliance cartridge, am I wrong? I have also read that 15 is medium compliance. I will check into the resonant frequency. How do you calculate it? VPI told me to get a headshell weight which I am pursuing. I have added weight to the tonearm (4 grams) and it has made a difference. Backgrounds are quieter, images are more solid, massed violins have more definition and do not sound smeared, it is much better. When I get the VPI headshell weight, it will probably even get better.
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