But that's not a high-frequency horn
I'm talking about that tiny horn on the coaxial. That's just no good for pattern control, and it shows in the off-axis measurements.
Yes, I'm already well aware of the limitation of the small horn mounted on the center of the woofer. This is not something I'm personally all that worried about -- I already foresaw fellow audiophiles foaming in the mouth due to the "small" horn size.