KEF's precise directional control is truly amazing.
First of all. Thank you very much for the measurements. Great job.
I wanted to comment your conclusion above. The directivity of this speaker starts to deviate horizontally around 2000 Hz. Between 2000 Hz and upwards it's overall uniform but not super constant. When we are below 2000 Hz we see that the directivity gradually get's wider. It's not too deviant to 1.5 kHz, but below 1.5 kHz it's collapsing with major changes. At 800 Hz the directivity is around 160°, and increase of approximately 60° compared to the higher frequencies. And below this it get's wider and the distinction from the higher frequencies increases. Obviously we don't care much about what happens below the Schroeder frequency, but we should at least consider the directivity down to 250 Hz area of a speaker.
Vertically, the speaker is much better. While it changes vertically from around 100° till 120° from 4 kHz to 2.5 kHz, it's able to remain a 120° directivty down to around 600 Hz.
I would argue that while it may be beneficial to remain horizontal directivity high in frequency (and especally when the horizontal dispersion is narrow), the directivity between approximately 500 Hz and 5 kHz is much more important to keep constant. This is the most sensitive area to us and deviations in the power response here will greatly effect the sound quality in a normal room with little acoustcial treatment.