I personally think technology has Improved for boxed speakers. I had a pair of Linn Isobariks DMS speakers, which were considered up there with the best available back in the 1970's/ 80's. Today I think they are bested by the ELAC cheap as chips range. I do not know what has changed internally with Klipschorns since they were first thought of by Mr Klipsch in the 30's, but I think my 'new' but old Klipshorns sound rather good to my ears.
Loudspeakers have we really made that much progress since the 1930s?
Since I have a slight grasp on the history or loudspeaker design. And what is possible with modern. I do wonder if we have really made that much progress. I have access to some of the most modern transducers and design equipment. I also have large collection of vintage. I tend to spend the most time listening to my 1930 Shearer horns. For they do most things a good bit better than even the most advanced loudspeakers available. And I am not the only one to think so I have had a good num of designers retailers etc give them a listen. Sure weak points of the past are audible. These designs were meant to cover frequency ranges at the time. So adding a tweeter moves them up to modern performance. To me the tweeter has shown the most advancement in transducers but not so much the rest. Sure things are smaller but they really do not sound close to the Shearer. http://www.audioheritage.org/html/profiles/lmco/shearer.htm