Loudspeakers have we really made that much progress since the 1930s?

Yes, this thread is very interesting and well worth reviving.  Since the last posts here, I am now running a 3-way vintage speaker built around a YL Acoustic (Yoshimura Labs) compression driver and horn.  To my ears, it provides a very natural, warm, dynamic sound.

Johnk, I noticed you don't have an AudioGon system page with details of your setup.  Any chance we can twist your arm and get you to post a description and perhaps some photos?

I thought that for the horn to go very low it had to be the size of a house. Was I wrong?

I looked up the YL and saw that both of you guys were discussing this on the Hoffman forum. Someone else on one of the fora had mentioned Deja Vu recently, in connection with recreating old WE horns. 
I've been using a commercial horn system (Avantgarde Duo) for 11 years and love their strengths- the "bespoke" vintage approach fascinates me- if it could sound coherent between the bass and mids, which has always been the challenge for me. I had also seen anecdotal reports on the GIP but have not heard any of these recreations. It sounds like the YL is actually vintage recreation which is appealing if it isn't as costly as some of the WE or other early stuff.
I just got my Quad based system restored, and as noted above, within their limitations, using restored Quad IIs with real GEC glass, they are breathtaking to listen to. 
I guess on both systems, the horns (with Lamm SETs) and the Quad-Quad system, i live with their shortcomings to revel in their strengths. I wouldn't mind assembling an all out horn system, but for space and cost. 
Sidenote: sorry if I mentioned this before, but the one thing I like about the Avantgarde design is that the mid horn is run directly from the amp with no crossover. It is very transparent, and with an even better driver, this arrangement would make much sense to me-- so much is in the midrange and if you can avoid the crossover there, it would seem to allow optimal performance. The issue then becomes making the bass (and treble) cohere. 

At home I run 3-4 systems while I do run modern loudspeakers many advanced for my own enjoyment I run horn systems. Most are combinations of old and new but when I can I try  to experience the best of vintage stock. If I have stock I mod so I can reverse and return to such. My office mains are community leviathan mid bass horns with 4- 515b woofers modified TAD 2001 on a giant community 10 cell multicell horn. I use costly passive networks but otherwise this could have been set up in 1970s. I do run a massive modern sub built to look like a old RCA MI booth monitor just much larger. My main system is 2-RCA MI shearer horns Viva amp I again run audiophile passive and use with fostex t500amk2 or faital driver on small 15 cell. 3rd systems 1920s RCA W bin with RCA radial horns and drivers and faital on matching tweeter horn again modern networks I use this at times with a massive front loaded bass horn. My garage system is a giant 1920s pair of RCA horns I used the RCA drivers at times but enjoy swapping in modern drivers my RCA drivers are  95 years old and I like to keep them functioning. I am all over social media you can google search if you want far too many pics.