I've been commissioned to build an ES-600 Biradial (600Hz Fc) using a 1" throat instead of the normal 1.4". The customer wanted to use a TAD TD-2002 compression driver. The horn flare is completely custom to perfectly match the driver's exit angle. I just happen to have another customer's pair of TD-2001 drivers here to test before shipping the horns. So I've done a complete set of measurements on the horn. This is the first time for me making a 600Hz horn using a 1" throat. As you'll see this provided some fantastic off-axis performance. I've also included my subjective listening impressions.
https://josephcrowe.com/products/copy-of-es-600-bi-radial-wood-horn
https://croweaudio.blogspot.com/2020/04/es-600-biradial-with-tad-td-2001.html?m=1
https://www.instagram.com/p/B-d0BHiJZmu/?igshid=1a7jd8zdtkddy