Hi Will, thank you for the dispersion diagram. Because of my room irregular boundaries (no right sidewall on the right speaker I have put bass traps 3 ft behind speakers and improved low level detail greatly. My room have has resonances at 33 and 39Hz which does wonders for the sound of the tympany.
I do have some concerns about the dispersion diagram accuracy. I have attached a polar frequency response graph for the Quad 57 speakers which has a fair amount of detail. The column width of the 745 is about 5″ which is the wavelength of 2700Hz. The adjacent column angle of the 745 is 7.5° while the Quad plotting angles are 10° each. I don’t understand the positioning of the -6dB point or how it is derived.
The pictures of your system I assume are taken at your home in Japan.