Sennheiser HD 700 Headphone (Jack plug &frac14;&rdquo; (6.3 mm) stereo) Specially-tuned, highly efficient drivers capable of delivering high sound pressure levels and a flat frequency response. Nominal impedance: 150 ohms Highly optimized ventilated magnet system minimizes air turbulence and harmonic, intermodulation distortion. Sound pressure level : 105 dB. THD, total harmonic distortion is less than 0,03 percentage Open-back ear cups facilitate transparent sound while showcasing cutting-edge industrial design