MM vs MI vs MC

[somebodyelse]

Does anyone here have the means to measure/quantify stiffness in a cantilever?

There was a thread starter about measuring cantilever resonance which is what matters in the cartridge. No replies, so I don't know if anyone here tried it.

 

[SIY]

Could you point out examples of such reviews?

Every one in Audio and HiFi News & Record Review. And quite a few threads on cartridge measurements on this site. Likely many others, but I don't read audio magazines much, so couldn't tell you who includes measurements and who doesn't.

Every test record I'm familiar with has a square wave cut, so it's routinely presented.

Here's some snippets from old Audio reviews.

 

[Nutul]

There is no mechanical difference between a MM and an MC

Thank you, I do know how MM and MC mechanically work.

My question, though, was about MM (moving magnet) and MI (moving iron...???), not MM and MC.

 

[JP]

Exactly how it sounds - there a magnetic alloy attached to the cantilever that moves within a fixed magnetic field.

 

[somebodyelse]

Exactly how it sounds - there a magnetic alloy attached to the cantilever that moves within a fixed magnetic field.

In case the rest of the steps aren't obvious: The magnet and coils are fixed in the body. The movement of the iron/other magnetic alloy within the field alters the field in the coils, inducing voltage.

 

[JP]

In case the rest of the steps aren't obvious: The magnet and coils are fixed in the body. The movement of the iron/other magnetic alloy within the field alters the field in the coils, inducing voltage.

Not necessarily. For example, ADC put the magnet in the stylus “carrier” assembly.

 

[dlaloum]

Typo? 19kHz would be more typical for cantilever resonance.

Yes, thank you . that should have been 19kHz... will edit!

 

[dlaloum]

There was a thread starter about measuring cantilever resonance which is what matters in the cartridge. No replies, so I don't know if anyone here tried it.

the Cantilever resonance is usually used to refer to the low frequency spring resonance of the cantilever system.... stiffness and its impacts are a different thing altogether

 

[dlaloum]

Thank you, I do know how MM and MC mechanically work.

My question, though, was about MM (moving magnet) and MI (moving iron...???), not MM and MC.

Again not mechanically different... MI has a largish magnet "inducing" magnetism in a piece of magnetic metal on the end of the cantilever... which in turn then acts like a MM design - it is mechanically the same ultimately.

Grado have used MI, and others over the years... but once rare earth magnets became available, allowing small light magnets, there was no real technical reason for MI anymore. In theory the moving iron would be lighter than a moving magnet, particularly with old style non rare earth magnets... but in practice the benefit was always marginal - still we are talking about very very small masses having outsize impacts in terms of resonances etc...

 

[Nutul]

Again not mechanically different... MI has a largish magnet "inducing" magnetism in a piece of magnetic metal on the end of the cantilever... which in turn then acts like a MM design - it is mechanically the same ultimately.

Grado have used MI, and others over the years... but once rare earth magnets became available, allowing small light magnets, there was no real technical reason for MI anymore. In theory the moving iron would be lighter than a moving magnet, particularly with old style non rare earth magnets... but in practice the benefit was always marginal - still we are talking about very very small masses having outsize impacts in terms of resonances etc...

Thank you for the detailed information and explanation; as weird as it may sound, the whole internet has not been able to provide me such a thing, even after a good one hour of searching and reading...

 

[dlaloum]

Thank you for the detailed information and explanation; as weird as it may sound, the whole internet has not been able to provide me such a thing, even after a good one hour of searching and reading...

There are lengthy in depth technical discussions going back years on VinylEngine - although I have noticed that some of the key participants in those discussions, are now to be found here on ASR.... (The tech geeks always gather together )

 

[Palmer]

I had two (actually three, but the 1800 did not make it) Bang und Olufsen come through, odd enough - but my first contact with Moving Iron carts, the MMC 5.
It was okay on a Beogram 5000 - but I managed to get a hold of an MMC 3 (with the 1800), now on a pristine 2000 - I must say I am pretty impressed.
Will never understand BO's numerology or names - The lower the number on the on the cartridge, the higher the class of it - on the turntables itself, it's the other way around.

 

[dlaloum]

I had two (actually three, but the 1800 did not make it) Bang und Olufsen come through, odd enough - but my first contact with Moving Iron carts, the MMC 5.
It was okay on a Beogram 5000 - but I managed to get a hold of an MMC 3 (with the 1800), now on a pristine 2000 - I must say I am pretty impressed.
Will never understand BO's numerology or names - The lower the number on the on the cartridge, the higher the class of it - on the turntables itself, it's the other way around.

Those are great cartridges, and relatively unknown in the marketplace....

Soundsmith purchased the rights to the technology from B&O some years back, and have then used it both in B&O compatible mountings as well as in 1/2" standard cartridges.

Anyone looking for a true high end MM (/ MI) cartridge could take a look at the Soundsmith range...

And they have low output MI's at the top of their range, to compete with high end MC's (they call it their "fixed coil" cartridges.... which is an apt description for any MM or MI... marketing speak!)

https://www.sound-smith.com/cartridges/fixed-coil/hyperion-mkii-mr

And their B&O mount cartridges:

https://www.sound-smith.com/bo-cartridges

 

[watchnerd]

Unfortunately, I have to go to work, so I can't get into much detail here. But... a DMM will almost certainly not work for this. You need to disconnect the cartridge, inject a square wave through a large value resistor, tap the preamp circuit before the EQ is applied, then use an oscilloscope to measure the rise time and back calculate the capacitance from t = RC.

It's not trivial which is why hardly anyone (besides me) does it in phono preamp reviews.

What about if I just want to measure the input capacitance of the MM in out of the integrated amp?

 

[JP]

Same.

 

[watchnerd]

Same.

How do I tap the preamp circuit before EQ is applied for an integrated amp?

 

[SIY]

How do I tap the preamp circuit before EQ is applied for an integrated amp?

That depends on the circuit topology. Sometimes you can't, as a practical matter (e.g., a circuit with feedback EQ looped back to the input stage). So... it takes a little more cleverness, a good scope, and a 10x scope probe, and you have to monitor directly at the input.

 

[RZangpo2]

I’m having a problem with a Shure V15V-MR cart that I’m hoping wiser heads than mine can help me solve. It’s mounted on an SME 3009 Type III arm.

In 2023 I measured the frequency response of the cart using two different original VN5MR styli (I have a small stock of NOS examples). Measured response was reasonably flat, as one would expect.

Recently, frequency response has sounded off. I measured again, and found rising response below about 100Hz, reaching more than +10dB at 20Hz! Of course this is audible; records with a lot of bass energy are almost intolerable.

I’ve checked setup. I’ve swapped styli without significant effect. I can think of only two explanations, but before acting on them, thought I would ask your opinions:

Tonearm resonance. The only change I’ve made to tonearm setup since the earlier measurement is that I now use the fluid damper. This results in much lower interchannel crosstalk measurements. Separation is greater, and the noise floor lower.

Disabling the damper would be a chore. I don’t see how it could be having this effect, but it is a variable.

Cartridge body. Could the cartridge itself have gone bad in the past couple of years? I have one or two other V15V cartridge bodies, and could try swapping them out.

Believe it or not, I’ve never done this. Swapping V15V styli is trivially easy, so I’ve only done that. On the SME arm, alignment is effected by moving the arm assembly back and forth using a rack and pinion system, so I haven’t had to touch the cartridge installation for that reason either. This isn’t the best time for me to start fooling around with this, but I will if I have to.

Is there something I’ve overlooked? If any of you can think of a better explanation, please tell me so. Thanks.

 

[Palmer]

I’m having a problem with a Shure V15V-MR cart that I’m hoping wiser heads than mine can help me solve. It’s mounted on an SME 3009 Type III arm.

In 2023 I measured the frequency response of the cart using two different original VN5MR styli (I have a small stock of NOS examples). Measured response was reasonably flat, as one would expect.

Recently, frequency response has sounded off. I measured again, and found rising response below about 100Hz, reaching more than +10dB at 20Hz! Of course this is audible; records with a lot of bass energy are almost intolerable.

I’ve checked setup. I’ve swapped styli without significant effect. I can think of only two explanations, but before acting on them, thought I would ask your opinions:

Tonearm resonance. The only change I’ve made to tonearm setup since the earlier measurement is that I now use the fluid damper. This results in much lower interchannel crosstalk measurements. Separation is greater, and the noise floor lower.

Disabling the damper would be a chore. I don’t see how it could be having this effect, but it is a variable.

Cartridge body. Could the cartridge itself have gone bad in the past couple of years? I have one or two other V15V cartridge bodies, and could try swapping them out.

Believe it or not, I’ve never done this. Swapping V15V styli is trivially easy, so I’ve only done that. On the SME arm, alignment is effected by moving the arm assembly back and forth using a rack and pinion system, so I haven’t had to touch the cartridge installation for that reason either. This isn’t the best time for me to start fooling around with this, but I will if I have to.

Is there something I’ve overlooked? If any of you can think of a better explanation, please tell me what it is. Thanks.

I had the SME 3009 III with the damping trough for quite some years, never really a problem... You can always just unscrew the paddle from the arm and, if you don't want to pull it out - move it, so you can test the table/arm without the damping. You have to push the stem down and out after removing the screw but it's easier than getting the whole trough off the arm. That would eliminate that equation without the fuss... Looking forward to the results.

Cheers...

 

[RZangpo2]

I had the SME 3009 III with the damping trough for quite some years, never really a problem... You can always just unscrew the paddle from the arm and, if you don't want to pull it out - move it, so you can test the table/arm without the damping. You have to push the stem down and out after removing the screw but it's easier than getting the whole trough off the arm. That would eliminate that equation without the fuss... Looking forward to the results.

Cheers...

I had the same idea myself about unscrewing the paddle. Tried it and found that it exaggerated the bass even more from 40Hz on down. So that idea was a bust. I will try to swap out the cartridge next, unless someone has a better idea.

EDIT. Does the worsening of the problem without the damper mean that it really is a resonance? If so, what could be causing it?