Help Harry!! I need your clarification on an older JMW9

Help Harry!! I need your clarification on an older JMW9

Postby Vear » Sun Aug 11, 2019 11:13 am

Hi Harry-

I'm new to VPI and had a question regarding the effective mass of the tapered (aluminum?) tonearm on my original Scoutmaster. I figured I'd go right to the source, I'm sure that you'll definitely be able to shed light on this. Below is the link to the thread I posted in the Support section with my original question:

http://vpiforum.com/viewtopic.php?f=12&t=12054

I hope you can clarify things for me.

Thanks in advance.
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Re: Help Harry!! I need your clarification on an older JMW9

Postby Brf » Mon Aug 12, 2019 9:27 am

I will let Harry chime in if my info is incorrect but what you have is a JMW 9T (one-piece aluminum tapered arm wand, standard Discovery wiring) which has an effective mass of around 9.2 grams.
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Re: Help Harry!! I need your clarification on an older JMW9

Postby Vear » Tue Aug 13, 2019 1:52 pm

Brf wrote:I will let Harry chime in if my info is incorrect but what you have is a JMW 9T (one-piece aluminum tapered arm wand, standard Discovery wiring) which has an effective mass of around 9.2 grams.


I looked into this a little more and just based on internet pictures out there there seems to have been an aluminum 9" arm that appears to be straight with a collar by the female cup. Maybe that is the 7.7g arm I was reading about??? So it seems that earlier Scoutmasters had the collared aluminium and later ones had the tapered aluminium (9T), is that correct?

I really hope @Harry does reply with confirmation/clarification as to the mass of the 9T. I get that the 9T added damping and mass but I'd like to know exactly what I have here. The VPI office is still telling me it is a 10.2g arm and now I'm not so skeptical but your're thinking it's ~9g so I'd still like to know for sure.
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Re: Help Harry!! I need your clarification on an older JMW9

Postby Vear » Tue Aug 20, 2019 2:26 pm

@Brf, Harry hasn't chimed in so I'm still not sure what the effective mass of this JMW 9T is. I found an older thread where the same question was asked and Mat left it for Harry to answer since it was before his time, but Harry never responded to that thread.

You seem to think it's ~9g (which lines up with other things I've read) but Customer \Service at VPI is telling me that their "lead tonearm technician that has tested every tonearm" (I don't have the individuals name) say's it's 10.2g.

You seem to be very knowledgeable regarding VPI products. Does that make sense to you?
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Re: Help Harry!! I need your clarification on an older JMW9

Postby Stringreen » Tue Aug 20, 2019 6:30 pm

..just wondering why your interest in the mass... I suspect most any cartridge is fine.... ( maybe I'd stay away from Grado)
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Re: Help Harry!! I need your clarification on an older JMW9

Postby jonathanb » Tue Aug 20, 2019 7:09 pm

If you have a test LP that contains resonance test tracks, you can determine the effective mass of your tonearm by using the following effective mass calculator: https://www.vinylengine.com/cartridge_d ... Calculator
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Re: Help Harry!! I need your clarification on an older JMW9

Postby Vear » Tue Aug 20, 2019 8:14 pm

Stringreen wrote:..just wondering why your interest in the mass... I suspect most any cartridge is fine.... ( maybe I'd stay away from Grado)


I just like to know exact details. Especially when it comes to something like a TT set-up. I have a sealed NOS high compliance (30@10Hz) cart that weighs ~5.5gr. which would be out of the ideal resonance range on a 10.2g arm. Yes it would sound fine, but I just like to know what I have.

jonathanb wrote:If you have a test LP that contains resonance test tracks, you can determine the effective mass of your tonearm by using the following effective mass calculator: https://www.vinylengine.com/cartridge_d ... Calculator


Unfortunately I don't have a test record like that. I just assumed it was easier to get a definitive answer on such a basic question from a smaller family owned shop. There seems to be a lot of different numbers posted out there for these older arms. I'd run with what VPI customer service told me but it contradicts everything I have read to date on every forum and review regarding these older arms.

It would be nice to have the guy who was there set the record straight.
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Re: Help Harry!! I need your clarification on an older JMW9

Postby edw » Wed Aug 21, 2019 1:18 am

you could try to get a good estimate...

www.audio-creative.nl/wp-content/upload ... -mass.xlsx
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Re: Help Harry!! I need your clarification on an older JMW9

Postby Harry » Sat Aug 24, 2019 1:52 pm

It's between 7.7 and 8 grams depending on the date of manufacture and works perfectly with anything over 15 compliance.

HW
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Re: Help Harry!! I need your clarification on an older JMW9

Postby Vear » Sat Aug 24, 2019 3:20 pm

Harry wrote:It's between 7.7 and 8 grams depending on the date of manufacture and works perfectly with anything over 15 compliance.

HW


THANK YOU!! I had feeling that this one was not a 10.2g arm. So I assume this Tapered arm and the earlier straight aluminium arm are the light ones.

Can you tell me how to identify the first models that went to 10.2g? That could be useful info if looking to buy used arm.
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