What I'm looking for is not nearly as likely to produce something known to be good. Perhaps that's the point for me. Does that make any sense?
Makes sense to me, and I've been loving these Popular Mechanics links you've been finding.
I've been involved with audio for years as a musician, but just for a year or so on the DIY side. I'm still a nephyte, but there are a ton of generous people on this site and others that are happy to share their expertise.
AND, horn enclosures sound cool. The center speaker in my avatar is an old Jensen designed cabinet from 1952, a 'compact' rear loading folded horn. Thanks to Zilch and a lot of other people here and diyaudio.com, we frankensteined it into an amazing sounding fusion of 50's and 21st century technology. (zilch-modifed econowave crossover, selenium 220i, QSC waveguide, JBL 2220).
My advice: Build
one. There are a ton of good full range drivers available for not that much money. Just watch out for efficiency--some of the drivers are very inefficient, not that great if you're running a low wattage tube amp. Play some mono stuff through it. If you love it, build a companion for it. If you don't love it, you will have had some fun and learned some things.
Horn enclosures sound so different from the normal box bass reflex ported speaker.