Take one of the best materials for high tones drivers, Beryllium, one of the best loudspeaker manufacturers, Pioneer (one of the oldest as well), engineer carefully for lowest resonance peaks and best dispersion - and you've got a best-selling line of separate ribbon tweeters available.
Pioneer's original craft was manufacturing loudspeakers, drivers even, but not separates.
As a result, PTs, HPMs and TAD loudspeakers are very present worldwide... whether in Pioneer's high-end audio units or even in in-car OEMs !
Powering the R7III is an AlNiCo 750 magnet of 7400G which allows a high 97,5dB /1W /1m sensibility. The shape of the beryllium leaf itself improves rigidity and extends the available frequency range of the piston movement ; the high-compliance edges of the leaf are sandwiched between silicon dampers.
Low-inductance power-supply, matching transformer with a sandwich of multi-layered windings of oxygen-free copper foils and permalloy core, gold-plated contacts and then some.
The PT-R7A was used in the S-955, the R7III in the updated S-955III.
Several other versions would see the light of sound later during the 1980s : R9, R6, R4 - all still sought-after for multi-amp active systems and commanding about the same prices as when they were available new - up to 130,000¥ for a pair of PT-R9 !