Horns

Auto-tech has been making many high-quality horns for a few decades their new company http://horns.pl/en/speaker-sets/universum-3-way/  is based on long-established DIY offerings and would be a great choice. 

You said {For example those awful JBL speakers used in so many mastering studios for decades should be proof enough}. So what models of JBL are you referring to and when did you own or hear any of these JBL horns? 

Don’t listen to the audiophiles who assume all horns have a sound that is mostly negative. Much of the audiophile music that’s so cherished today was mastered on horn systems. Yet audiophiles will say you need to play back the way the artists intended then they proceed to play that wonderful Jazz or blues mastered on Altec TAD and RCA horns on a small chinless dynamic bookshelf or slim tower. Many of them have never owned horns or had any real experience with the many types of horn systems available. They have been told that horns are problematic. An old tail made up by 1950-60s audio salesmen to get mono speaker owners to dump the wonderful JBL Hartsfield for a crappy pair of AR. The old sales lines have been passed down by the audio press as facts. Just like they did with tube amplifiers and turn tables. Later they were proven very wrong it’s the same with horn designs.

List your vast horn experience. And please link to all these reviews based on listening tests that prove the point you try to make on horn loudspeaker systems. Or was I also wrong about how the press covered tube amplifiers and early digital? 

No Japanese twins with straight pipes.  I design loudspeakers, and I also collect and restore all types inc horns I'm well-known in this hobby people come to me to design products or appraise identify or retell the history of rare audio. I tire of those who pass about hearsay and bias as facts while not having any hands-on experience.