Problem is you are misinterpreting specs. In order for the compliance to be the same the dynamic and the static would have to be the same, but they are not. They also don't measure the same. On the same arm you will get a lower resonance number on the VM500/700 series vs. a higher one on the VM95 series. THAT IS BECAUSE THE VM95 SERIES HAS A STIFFER SUSPENSION. That's per measurements, not calculators and conversion multipliers.
The best thing to do is to ignore the factory specs because they won't help you with Western-style calculators. Instead I use resonance numbers from actual measurements on my gear, and have looked at 3rd party lab tests and what other people measure. That is a far better guide than multipliers, which are often flat out wrong or off by a significant amount when it comes to Japanese cart specs.
RE: a 15g EM arm, I would consider that well within medium mass. Anything from 12 to 20g or a little bit more can be considered broadly medium mass. A 12g arm offers some flexibility with the choice of cart, it's sort of a "tweener" arm, if you will. An arm like that can take a broad range of carts. As the arm gets heavier, the higher compliance carts aren't going to work quite as well, unless the arm has some kind of special damping feature or the cart has the old style damper brush that Shure and Stanton used to use.
RE: capacitance, math and measurements tell us these are sensitive to loading just like any MM cart with a certain amount of inductance. It is not hard to stay below 200pf total if you know what you are doing. The problem is a lot of people do not. They get one of these carts, and then plug it into a crusty, old 70s receiver phono with way too much capacitance (e.g. designed for 70s carts that needed a ~300-400pf total load) and then wonder why it sounds bright. Typically these people don't own a test record and a sound card/audio interface so they can't measure the FR either to see that their loading is wrong, they have no idea about their receiver phono spec, etc and they never read the cart manufacturer's loading recommendation either.
With a phono preamp with no more than 100pf input capacitance and low capacitance cabling it is not difficult AT ALL to achieve the ~200pf load. Many newer phono preamps are spec'd with 100pf nowadays. Not all, of course, but they are not hard to find. There are also phono preamps with even less capacitance than that, if you shop around.
Well, I was tempted not to reply to this message, as I interpret bold text as someone shouting at me. However, this will be my last entry in this thread.
First of all, I'm sure you know more about compliance testing than I do, accepted. However, I imagine that AT made actual measurements for their dynamic compliance figures and didn't just pull them out of thin air, so I'm not entirely sure why you're choosing to discard them (even if they are at 100Hz). On the other hand, I find it odd that these two AT cartridges have the same published dynamic compliance but different static compliances, so I agree that there is something fishy going on and see some justification for your scepticism about these measurements.
You say anything from 12g to 20g is classed as medium-mass (Ortofon say 11g to 25g) but that there is some flexibility at the 12g border. You talk as if this discrete value is special, which seems somehow 'digital' to me, while the natural world is analogue and I would expect the 'flexible' zone to be somewhat wider. Indeed, 15g is well within the medium-mass range but I was saying that I had used the AT-VM95E successfully on a 15g arm, while I understood that you were suggesting that the AT-VM95 cartridges are only suitable for arms at the high end of medium-mass, which I would intepret as some way above 15g. Perhaps there was some misunderstanding here.
I have a phono pre-amp with selectable capacitance in the range 50-400pF, so I am able to experiment with capactive load on all my cartridges, although I don't modify cables (I'm not that practical). The typical capacitance of the cables supplied with a turntable is usually taken to be around 150pF. So not to exceed a 200pF total load, you'd need a phono-stage of 50pF capacitance and there aren't many of those around, most being at least 100pF and many at 200/220pF. So, the main option for lowering load capacitance would seem to be replacing cables and I don't see this as an easy option me or the average vinyl enthusiast, hence my assertion that a capacitive load of 100-200pF is difficult to achieve in practice.
Finally, "the proof of the pudding is in the eating" - I'm not sure whether you have this expression in the US? I have a wide range of cartridges and while I wouldn't go to extremes to violate the effective-mass/compliance matching, I find that many (even most) high-compliance cartridges work wonderfully on medium-mass arms - they sound great and they track warps without a hitch. Agreed, some high-compliance cartridges do seem to favour lighter arms, the Grado Prestige cartridges being an example, even though their published dynamic compliance of 20 suggests that they are only borderline high/medium-compliance - perhaps this is one example of not relying too much on what the specs tell us.
