The HD measurements at distance 315 mm and voltage levels 2.83 - 16 Volt were carried out with High Pass Filter "on" (2nd order Butterworth type, 50 Hz cutoff, HPF2-50)
The HD measurements at distance 20 mm and voltage level 8 Volt were carried out with High Pass Filter "on" (2nd order Butterworth type, 20 Hz cutoff, HPF2-20)
Before taking the measurements the speaker had been very good boken-in