The diameter of the wire is also a component in deciding the sound, so rather than using the thinnest possible wire, a cartridge maker is likely to use whatever wire diameter that he (or she) thinks will give the right sound. In production you can go down to 15 micrometers (or even 12 if you don't mind somewhat higher than normal wire breakage), but based on my personal experience, I'd estimate that the Eminent, SPU Synergy and Orpheus all use considerably thicker wire - probably something on the order of 40 micrometers or even 45.
I quite agree with you that yokeless designs have certain advantages over traditional designs with polepieces (yokes). I simply don't agree that higher output efficiency is one of those advantages. Actually, if it is only output efficiency that you are pursuing, a traditional polepiece architecture is the easier one to do, first because the size of the magnet in a polepiece-based design can be far larger than what is practical in a yokeless design, and on top of that, the polepieces offer a greater degree of flux focusing than a magnet by itself can.
Incidentally, yokeless cartridges have been out on the market from the late 1970s, while as a subset of yokeless, designs involving ring magnets that fully surround the coils have been out since at least 1981, possibly earlier. So already a bit of time has elapsed since their introduction, certainly enough to refine the general concept :-). I do reckon that it is possible to refine the yokeless concept further, but then the same thing can likewise be said about polepiece-based designs. IME, neither one is maxxed-out yet, and each has a distinct set of trade-offs (advantages and disadvantages). A cartridge designer may validly prefer either, depending on his design goals, insights and resourcefulness.
I quite agree with you that yokeless designs have certain advantages over traditional designs with polepieces (yokes). I simply don't agree that higher output efficiency is one of those advantages. Actually, if it is only output efficiency that you are pursuing, a traditional polepiece architecture is the easier one to do, first because the size of the magnet in a polepiece-based design can be far larger than what is practical in a yokeless design, and on top of that, the polepieces offer a greater degree of flux focusing than a magnet by itself can.
Incidentally, yokeless cartridges have been out on the market from the late 1970s, while as a subset of yokeless, designs involving ring magnets that fully surround the coils have been out since at least 1981, possibly earlier. So already a bit of time has elapsed since their introduction, certainly enough to refine the general concept :-). I do reckon that it is possible to refine the yokeless concept further, but then the same thing can likewise be said about polepiece-based designs. IME, neither one is maxxed-out yet, and each has a distinct set of trade-offs (advantages and disadvantages). A cartridge designer may validly prefer either, depending on his design goals, insights and resourcefulness.