The HD measurements at voltage levels 1.41 - 8 were carried out with the 2nd order Butterworth type High Pass Filter (800 Hz cutoff, HPF2-800)
The HD measurements at voltage 11.2 were carried out with the 2nd order Butterworth type High Pass Filter (1000 Hz cutoff, HPF2-1000)
The voice coil current HD measurements were carried out with the 2nd order Butterworth type High Pass Filter (800 Hz cutoff, HPF2-800)