Clearly the 100Hz reference is a direct and mistaken ripoff from the original 1945 Klipschorn patent document, which was concerned with a smaller version featuring a single 12" field coil driver which DID indeed use a 100Hz flare rate at the throat. So much for copying the at-the-time-and-still-current-flavor of the larger 15" driver version of the Klipschorn and not knowing why it's the way it is...

However, the 1970's Speakerlab "K" used the familiar 15" driver and the normal 50Hz throat expansion rate, as indicated in the Speakerlab "K" plans. Anyone with a ruler can figure it out. Wavelength/18.1 = exponential area doubling length, and that isn't going to amount to 100Hz (that would double its area every 8 inches (approx) of linear travel)!

The throat area cross-section doubles, according to the plans, at at approx. 16 inches, measured center of channel, which would be 50 Hz, thereabouts.

DM