Horn Speaker Recommendations

I have not heard the PureAudioProject speakers, but I like the looks and I like the concept.  I like open baffle speakers, but, if deep bass is a must, I would caution that a relatively narrow open baffle speaker can be expected to roll off in bass response because of out of phase cancellation between the forward moving wave and the back wave.  The open baffle woofer speakers that I've heard with somewhat deep bass (not really that deep), had pretty large baffles to reduce front and back interaction.  Most recently, I heard a system with twin 18" fieldcoil woofers in a baffle that was about five feet wide.  The Shearer systems that Johnk mentioned had baffles much wider than that.

roxy54 never mentioned rare or costly you did. I can put something together that’s better than most audiophile horn offering for about 2000. And of coarse system end goals are what matters  I want a great sounding horn good is pretty easy to find most any horn is good.

 But sadly with horns, the audiophile market isn’t offering many worthy of purchase unless you want a hybrid horn and honestly if I had to go that route I would buy a conventional dynamic

interesting. What are the problems with Hybrid system like JBL 4429/4430/4367.
what are the advantage a full ragne horn system?

1) JBL DD 67000 New $85K Used about $30K
2) JBL 4367(I own) New $15K Used about $9K
3) Klipsch Klipschhorns

Great old American speakers. There is NO substitution for 15" woofers! 

I’d be looking at vintage Altec over Klipsch. 
I’ve owned all of them and the best are the 500 cycle horn (511) systems like the Heathkit designed Legato
and Altec Laguna or A-7 ( Magnificent) Maybe harder to source than Klipsch.  Better yet, get the parts and build your own mock up to suit you and your room. Research the different LF systems. 
2-15’s sealed, 1 15 in A-7 horn, Onken. 
Not as hard as you’d think.