Tubegroover, Regarding CLS from the mid 80's. That speaker was more sensitive to amplifiers than most speakers. Infact it was extremely sensitive to everything in the system. It was hard to find a solid state amplifer that did not sound thin. One the other hand it was easy to find a tube amplifier that would give the speaker a balanced sound. The impedance of the CLS was very low at high frequencies and very high at low frequencies.
The most revealing speaker I have ever owned. I was fortunate enough to have a variety of amplifiers on hand to find the right match. Without that luxury I could see how frustrating it would be.
Regarding high frequencies, I believe the CLS was rolled off. However, the interface could be adjusted to your system and your taste.