...."dynapleat" drivers, as they were called when first distributed in the US in the mid 80's. More recently, they were called "dynaribbons", and variations were used in some very pricey speakers from Mavrick (Non-speakers) and VMPS, as well as by Sawafuji in their box speakers, as well as their large panel speakers, which used these drivers as both bass and mid drivers.
They seem to work quite well in the 400 - 5KHz range, but do not perform quite as well as bass drivers, which is why Sawafuji came out with the more conventional box designs where they are used as mids.
Initially, they were distributed in the US by SFD (Sawafuji Digital), which later became SFI USA. I don't think SFI is in business anymore, althought the Japanese parent company, Sawafuji is still around. Don't think the Dynaribbons are made anymore either, but they do turn up as surplus from time to time which is how I collected mine.
