What is the impedance and the sensitivity for the headphones?

The impedance magnitude of the M1570 is basically flat at about 58 ohms, and the phase response is very flat.
The sensitivity of the M1570 headphones, measured between 300Hz and 3kHz, using a 1mW signal calculated for 60 ohms rated impedance, is 101.1dB, much higher than the rated 96dB.