Old but still reading this entire comment sections. Boy o boy , so much misinformation here.
Infinity tweeters are NOT true ribbon drivers. They are electro magnetic induction drivers. Or in simple terms, planar magnetic.
True ribbons drivers do NOT always require a transformer. Apogee did that, because their design in the scintilla for example. Dipped to well below 0.5 ohm . They used a transformer to stabilize the impedance .
Magnepans , for example the mgIII,2.5qr, tympani IV had true ribbon tweeters. Without any need for transformers.
True ribbon differences are very simple to explain.
You have two rows of magnets , with in between a ribbon that's under tension. The ribbon gets actuated, by the magnetic field the two rows of magnetics create.
Planar magnetic, you have a a piece of mylar/kapton with the voice coil tracks bonded to it. And magnets were either behind or Infront of it (older models maggies for example were all single ended) or both (like emits ) they had bar magnets behind and Infront of the diaphragms being push pull.
in short they were having "heavier" diaphragms vs a true ribbon.
How I know ? I have about 10 sets of emit loaded infinties and 5 sets of magnepans..
They both have advantages and disadvantages.
True ribbon tweeters are notorious for their less than friendly crossover point. Planar drivers just do better there.
True ribbon also relies heavily on the magnetic field , not uncommon for them to start slacking , and need adjusting or replacing over time. They stretch and start slapping outside the gap they are in. Planar magnetic drivers are just way more sturdier, and could be implemented on lower crossover points.
true ribbon tweeters are incredibly fragile. A gust of wind can already rip them apart . Magnepan for example , will have magnetic strips on them to protect them during transport. Very fragile ..
It is a incredibly revealing driver , but imho I don't hear huge life altering differences between a true ribbon or a well build planar magnetic tweeter.
