Effective mass is not the same thing as mass.
Tonearms can have the same effective mass but different mass (weight).
It is certainly not that. It doesn’t matter that the Internet says it is… Its wrong.
So, in the real world, can an ARO2 be fitted to an LP12?
To-date, everyone has said “no.” Including I recall Peter S.
Perhaps attaching it with Blu Tack?
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My reply wasn’t aimed at you?
Too many Js!
J
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How to calculate Tonearm Effective Mass -
No one said it was easy… 
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I have spent some time trying to figure out the root cause of this entire problematic situation. And I keep going back to the ‘mistake’ in the documentation that shows the equinox at 8g when in fact it is 14g. Perhaps instead of merely being an error this was a fundamental misunderstanding between Naim and Clearaudio that explains everything. If this system would have been optimized for an 8g cart as specified in the spec then every cart on my ‘out’ list that represents 90% of the carts audiophiles use and are all in the 7.x to 8.x gram range would have worked. I have to wonder if the two companies were not on the same page and this is the evidence of that.
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And no one discovered that in testing? If Solstice were a space probe it would crash on the surface of Mars.
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Hopefully not a mix up with imperial and metric systems 
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That’s a great diagram. I suppose the weight of M4 affects a crucial part of the effective mass calculation, Z. I am probably simplifying things though.
Let’s hope that the destination wasn’t Jupiter!
Josquin correct it was not discovered in testing. Nobody weighed the cart…who would have? If someone sends me this turntable to test i would not have weighed the cart. A bigger question is was there a beta test program? A telling fact is that our host Richard Dane has never seen a Solstice. Is there a single person in the Naim community who has owned and used more turntables and carts than Richard? He is the kind of person who might have tried to use another cart and reported back that there was a huge problem.
Now you are just making stuff up, how do you know what testing was or was not done.
The fact that the manual is wrong is not good but that is much more likely to be a simple typo rather than Naim not knowing the weight of the cart
As an Engineer, I can say its a reasonable model of a Tonearm - but not necessarily very workable. Only m4 (the counter weight) can be determined fairly accurately, by measurement. m1 will be the sum of the masses of the cart & the headshell. The cart mass could be found - but unless the headshell is removeable, that would need calculation. m2 & m3 are based on the tube including whatever is inside - difficult to estimate that, without significant knowledge.
It shows that determining the Effective Mass of a Tonearm is not trivial.
I cannot believe this. But - it does seem odd that the Equinox’s mass is so high - compare to other (typical, similar) cartridges. And that its mass is incorrectly listed by Naim.
Perhapds @110dB could comment here…?
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It would fall over on the surface of earth. 
M1 doesn’t include the cartridge.
The effective mass is mass that would need to be added to M1, to balance the clockwise and anticlockwise moments of inertia.
In the case of a 14g effective mass tonearm M of I would be balanced by a 14g cartridge.
I think. 
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Very nice. The SPU Royal N is a cracking cartridge in the original ARO, so long as you use the heavy counterweight and add tiny bit more mass to the anti skate.
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