First, I would like to now your experience with super tweeters, please only the ones who actually tried them.I used Decca ribbons, and then Sequerra ribbons as part of a mini-HQD system many years ago with a subwoofer. They increased the frequency spectrum, but like most add-ons to the original Quad ESL (aka '57), there was a coherence issue-I did manage to get them to blend and I guess they accomplished part of their task in making the high frequency sweet spot (within the range of the super tweet) less constricted- a notorious fault of the old Quad.
Still have the Deccas, they need to be repaired. I kept them mainly for artifact value. Are the Townsends still in production? I think there was another brand in the last few years that is no longer in production?
Old school isn't it?
This came up in a discussion of the big Bozak, for which it was common to use some piezo tweeter as an add on....