Polar response of the tweeters:
At 800Hz the response shows nearly perfect dipole behavior
(-1dB at 30°, -3dB at 45°, -6dB at 60°). The wavelength is
43 cm and thus longer than the panel is wide. Front and rear wave can interact and the resulting sound power is at least close to 4.8dB, which is the typical value for an acoustical dipole.
Above 1KHz the response widens ("blooming") to dipole like behavior due to the relatively large panel size compared to the wavelength radiated. Starting around 3KHz, beaming of the tweeter counteracts the blooming and around 6.3KHz beaming and blooming are in balance. Further up in frequency the response narrows down as the beaming is progressing.
At 6.3KHz, the response is no real dipole response because at a wavelength of 5.5 cm the two tweeters are completely separated from each other by the panel. They have become single sound sources radiating into half space. As a result, the sound power rises by 3dB.