[THROWBACK]

I have a Miyajima Kansui low-compliance (7x10 ^-6) cartridge that supposedly requires a medium- to high-mass arm. Right now it is mounted on a Graham Phantom II Supreme arm. Sounds terrific, but could there be more? This enquiring mind wants to know.

First, I have found it nearly impossible to determine the effective mass of the Phantom II. I have seen several numbers. Michael Fremer says 11-12gm. I read "19 gm armwand" in another source. And I saw 9 gm somewhere else. Yes, I know there is some difference between "mass" and "effective mass," but my sources have been none too clear about what that means and/or how to use it--at least as far as I could tell.

But the upshot seems to be that the mass of the Phantom II is too low for the Kansui. Has anyone played with increasing the mass on the Phantom II to get a better cartridge-arm match? How'd ya do it and how'd ya know when you had added enough?

Thanks.

[THROWBACK]

Sorry. My italics went haywire.
THROWBACK

[Ericus Rex]

My Audiomods arm came with shims to put between the cart and headshell to add mass to the arm.  If you don't have or can't find shims you can test this out by adding weight to the headshell yourself.  You can tape a penny (about 3 grams) to the headshell and then reset your tracking force (important!).  If it sounds better and you can't find the right shims you can add mass to the arm with heavier mounting screws and nuts.

See how it goes.  I have a formula written down somewhere that allows you to calculate the effective mass of the arm yourself.  I'll look around for it tonight.  You might also find that formula yourself at a vinyl forum like vinylengine.com.

[neobop]

Small world.  If you go to mfg. web site you'll see compliance is at 100Hz.   10Hz cu is probably around 15 or 16. 

If it sounds terrific, I wouldn't worry about it.

neo

[THROWBACK]

Thanks for the replies, guys. The Kansui must be mounted with the nuts on top, so I can't use something like the Soundsmith knurled-top screws with their varying weights. Also, there is no room for a penny on the headshell. I have in mind something like a lead tape. We'll see.

[Ericus Rex]

No need to get too fancy.  Standard screws will work.  Stainless is heavier than aluminum which is heavier than nylon.  If you could find tungsten screws that would be even heavier than stainless.

[neobop]

I wasn't kidding.  That 7cu spec is @ 100Hz.
http://www.miyajima-lab.com/e-stereo.html

To estimate 10Hz cu used for calculations, see the 100Hz thread currently running.  You could always get a test record and have a good idea of the actual resonant frequency of the arm/cart.

The cart weighs 10.4g.  If the arm eff mass is 12g and screws weigh 1g - with a 10Hz cu of 15 you'll be somewhere near 8.5Hz.  If that is the case then adding more weight will take you lower, not higher in res frequency.
neo

[woodsyi]

If higher mass is desired (maybe not since Neo points out you are around 8.5) you can also get a longer wand (10" or 12") for your Phantom II, assuming you are at 9.  Longer arm should give you higher effective mass, I think.  Shouldn't it?

[neobop]

Yes, a longer arm will have higher eff mass.

I can't say I know exactly the equivalent compliance of the cart, but it clearly states 7cu @ 100Hz.  My estimate is based on other carts also spec'd at 100Hz, and their equivalent cu.  Because this cart weighs over 10g, which gets added in for estimates, I suspect messing with the weight will be counterproductive.

I've heard countless stories of people who couldn't leave well enough alone and broke something in their quest for perfection (including me).  As I said previously, a test record might be wiser than experimenting.  By all accounts that's a great cart.  Enjoy it.
neo

[dlaloum]

Another option - get one of the test records (I use HFN Test record) - and use the low frequency resonance track to determine what your resonant frequency is.

If it is too low, lighten the arm, if too high add more mass....

Anywhere between 11Hz and 9hz is good, between 12Hz and 8Hz is ok - outside of that it can get iffy...