That brings back a few memories. I owned a pair of the first 5's from 1968 until I replaced them with a pair of Proac Tablettes in the late 80's. When I bought them, the only real competition was from Acoustic Research, and I didn't like their murky sound signature, which came mainly from a bump in the upper midrange. The 5's were the most neutral speaker I could find, particularly in the midrange. A few years ago, I stumbled across a pair of used 5's in good working order and decided to hear and see what I was listening to all of those years. I was surprised to see how ragged the response was. The culprit was fairly wild cancellation effects between the tweeter and the dual, horizontally mounted mids (which were also used full range in the KLH radio and portable "suitcase" stereo). The mids were true acoustic suspension drivers, and measured very well on their own. Back then, cancellation effects weren't considered important, and weren't addressed in the crossover design (or couldn't be given the state of the art then). I've attached the on-axis response of the stock 5 on the tweeter axis. Things improved a little on the midrange axis, but were still pretty wild. Of course, I had to redo the crossover to see what the drivers could do when they weren't fighting themselves, and I was able to straighten most of it out--see second plot. So why did I like my original pair so much? It's because the 5 didn't have the untreated baffle step around 1 kHz that plagued most of the competition. I didn't really pick up on the big dips in the mid treble because other speakers at the time had similar problems with cancellation dips up there (the AR3a was a mess). The problem was obvious when I compared the stock with the modded version, which turned out to be a really nice speaker.
The updated 5 shown at CES strikes me as pure marketing hype. The original 5 was never all that popular, and the only feature that was remotely innovative was the use of acoustic suspension midranges. Also, the 5 suffered from being a downsized version of the KLH 12. The 12 used the exact same drivers, but in a much larger cabinet (with more pots for adjusting frequency response.) As a result, the 5's cabinet was too small for the woofer, and the bass was kind of boomy with limited extension (the cabinet tuned to 50 Hz, quite a bit higher than the AR3a, which also had an acoustic suspension woofer.) The new version doesn't use a true acoustic suspension mid or woofer, and the tweeter is just another conventional dome. It really bears no similarity to the genuine model 5, other than using a similarly sized cabinet.