I have the speakers finished last night. The first minute they sang immediately pulled me into the music and I couldn't stop playing disc after disc until 2am in the morning. It showed its authorities that I didn't have to play loud to feel the big impact and big/wide sound stage. I don't know how to tell my appreciation to hm. hm, you did have a wonderful design there. The speakers abilities to recover the music are astonishing. I can find those notes I can't hear on the other speakers before, even the big horn behind the picture shows some kind of weaknesses on body. I just can't imagine this little 3.5" speakers can create such a big and smooth sound stage. ( Both Dayton RS100-8, and Peerless TG9 are rated 4" but only with Sd around 36sq.cm so I thought they are actually a 3.5" drivers. The TG9 is not ideal for this application for its high Qts at 0.89 but no harm to try ).
The images are wide and tall, piano is grand, vocals are lush and lovely. Shirley Horn, Diana Krall and Eva Cassidy are all gorious to my ear. I could almost touch their throads. I played over and over almost all the sopranos I love and they are even more lovely in this speaker. The speakers give full body sound with layers detailing and mid basses are so tight and accurate. You will not be too surprised to hear some notes that you miss on other speakers, but in some ways the upper frequency region is surprisingly neutral, the most neutral I have ever heard.The bass is clean, fast and bass extension is not lacking, but the sense of weight and power is always there, the whole sound spectrum snapped into focus at a listening range. I've been making and finishing lots of speakers in the last 40 years, from BR to OB, from BLH to BIB, from big JBL 2446 horn to Bill's syergy horn. This is the only horn I could rate it second to Bill's syergy. But, for me, this one is easier to make and won't break my bank.
I have tried different amps with this speakers. The 6AS7pp provides very solid and strong mid/low bass, but sounds too much to my ear. The 300b sounds more liquid/delicate at highs and lovely mids but soft at bass region. The 6C33C OTL is just about right, it sounds almost in the middle of the two. After serious listening, I love the 6C33 OTL wide and deep sound stages than any other amp I built. May be it's the result of the wide bandwidth that it creates. On my test bench the 6C33 OTL shows the square wave ( all square ) from 15 - 31,000 and sine wave over 100k.
I leave 8 feet behind the speakers to the back wall so to ensure the best bass/mid balance, and a clean, open, airy sound stages. Thanks hm again for sharing/guidance and hope his idea is endless. I'd certainly go for the bigger one, may be a 5" or 8" in the near future.