[Bobsound]

I used to use Vitavox horns and GP1s and 2s in my PA hire business in the 70s and 80s. I believe these horns have a flare cut off frequency around 300 Hz.

I always considered the Vitavox equipment to be beautiful pieces of mechanical engineering. The multi cell arrangement was supposed, I believe, to overcome the 'focussing' of the sound into a narrow beam at high frequencies. I cannot speak personally how effective this was but quite a few reputable American manufacturers also produced multi cell horns.