I owned them for a year or two around 1976-77. Replaced with Quads. I don't think I ever powered them properly and, back in that day, we didn't know about putting them up on stands, break in, etc.. They really captured my fancy when I auditioned them (much as Avalons did 20 years later), but I came to feel that they sounded rather artificial and metallic and too "present", though you could adjust the levels on the mid and tweet. I blew out more than one tweeter, too. Great bass, though. Sealed box, right?
Would love to hear again in a modern system.