I've chatted briefly with Tom. His postings got me interested in 511s, as a matter of fact. He certainly was of the opinion that the Altec approach to midrange horns was better than Klipsch.
Tom is a wonderful fellow with lots of practical experience when it comes to hifi audio reproduction, too.
The classic Klipsch MR horns, and the cheap PA drivers they genearlly used with them, are horrible things to listen to.
I suspect PWK wan't being ironic when he embraced the term
squawker for midrange reproducers.
I cannot tolerate screetchy loudspeakers
Altec did much better, as did may others. As you know, I have been using EMILAR 500 Hz horns on my 'real' loudspeakers after trying quite a few of the affordable alternatives including the 511B.
... unfortunately, none of this will help a Zu owner, except (possibly) for
option creation -- but ASR folks in gerneral don't seem to be particularly interested in high sensitivity loudspeakers. Oh, well...
I still haven't heard the old Klipschorns like the La Scala. From what I understand, that might help me understand people's aversion to horns.
The LaScalas are unbalanced due to the size of the bass horn, with very little in the way of LF output. That's what makes them the hardest-to-take of the "heritage" Klipsch lot, for me.
I can absolutely tolerate the K-horns, but the best ones I've heard were so modified as to barely
be K-horns any more.
The Cornwall is likely the best compromise of the whole "heritage" line, having decent (
albeit bass-reflex and not horn loaded) bass reprduction. The 1974 Cornies I had were just too harsh overall, although I lived with them for a decade. Some recordings sounded very good on them; others were literally unbearable (at least in places) due to resonances in that MR horn. The current Cornwall IV might be OK -- they're ridiculously expensive, though, for what they are (and what they aren't), I'd opine.
The slightly later Klipsch Chorus ain't a bad sounding loudspeaker (FWIW).