How oldy are your speakers in rotation?

I worked with the TW010 on a project back then... If I recall, the 10mm voice coil had no former, the wire wound voice coil was glued directly to the polymer diaphragm. If I recall, Fs was really high, like 1.9k ? The impedance hump at resonance was very mild, so these were almost a pure resistive load.

Unfortunately, I could never get good sound from these tweeters. For a little more money, an Audax, Peerless,or Vifa 25mm dome was much easier to coax good performance from.

On the other hand, I was fairly inexperienced at the time, so perhaps the TW010 just needed a more knowledgeable designer than I was...

j.
 
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Had these Concertos since new in 1974, and they are still in daily use and sound awesome.
KEF Concerto2.jpg
 
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Those Audax tweeters were proper coil designs and not piezo as far as I know. They had a high natural resonance frequency and natural second order rolloff. When paired with a simple single cap crossover this formed a 3rd order acoustic crossover.

Those tweeters and their siblings were extremely popular back in the day.
I had coils in early factory Harbeth's, with silk domes and square mount plate. They were extremely sweet and still detailed.
 
I got my good old 1976 Goodman Mezzo SL, not my main set, but they got used often and will never be sold. In my kitchen i got some 1971 Philips 22RH412 speakers that are still exellent. And in my lab i use some old Philips AD1065 drivers in an old big cabs, not made for it, but fitting it very well and sounding surprisingly good.