Headphones HD 820 (closed, dynamic headphones)connection cable: (6.35 mm) stereo jack plug (connected ex works), unbalanced4.4 mm stereo jack plug, balancedUSB flash drive (SD-U16L version) with instruction manual (as PDF file) and individually diffuse-field frequency response curveinstruction manualstorage boxmicrofiber clothTechnical DataImpedance300 OhmsFrequency response (Headphones)12 - 43800 Hz (-3 dB)6 - 48000 Hz (-10 dB)Sound pressure level (SPL)103 dB at 1 kHz, 1V