1. DH 660 Stereo Headphone SPECIFICATION Characters Headphone with microphone Loudspeaker diameter 640mm Sensitivity 103dB S P L at 1KHz Impedance 320 Frequency Response 20Hz 20 000Hz Rated Power 100mW Cable Length Approx 2 5m Microphone Unit 6x5mm 58dB 2dB Plug Type 3 5mm Stereo am Dynamode