roughly measured real KZ ZS5 v1 sensitivity: it's not 106dB/mW SPL, as advertised. it's 99dB/mW (122dB/V) SPL, considerably lower, as suspected. (all measures were done with a @1kHz tone; used a cheap SPL meter, so consider +/-2dB error). made some measurements on Benjie S5 + SPC cable (6 cores, metallic straight jack) + KZ ZS5 v1. as suspected, maximum volume with no distortion is 10/31 (25mVrms/5.20mA); you get about 90.2dB SPL. when listening at that volume, found it too low for my taste (maybe because i'm used to louder-painful volume). from volume 11/31 to 14/31, distortion grows up. maybe you can accept distortion at 12/31 (39mVrms/8.12mA/93.9dBSPL), but at 14/31 (57mVrms/11.87mA/95dBSPL) you can notice it clearly. at 15/31 (68mVrms/14.17mA/98.6dBSPL), clipping occurs and distortion is extreme. highs become unbearable. that's what happens due to limitation of current in cheap DAPs and many smartphones. with such low impedance, zs5 are more current demanding. so you can listen to zs5 at benjie s5, but don't raise the volume too much (10/31 should be the limit, if you like clear sound).