Here's the specs for my PSB M4U 1 headphones:
Sensitivity average in band from 100 Hz to 10 kHz, dB/V
118,8
Impedance average in band from 40 Hz to 15 kHz, ohm
35,8
For 94,0 dB SPL need, VRMS
0,057
For 94,0 dB SPL need, mW
0,092
My listening volumes average...