Sennheiser  HD 300 Pro Studio Headphones 

• Impedance: 64 ohms
• Frequency response (Headphones): 6 Hz - 25kHz
• Max. sound pressure level: 123 dB SPL @ 1 kHz
• Contact pressure: 6.0 N +/- 0.75 N
• Ear coupling circumaural
• Power consumption: 500mW
• Storage temperature: -55C to +70C
• Operating temperature: -15C to +55C
• Distortion: less than 0.1 % @ 1 kHz, 100 dB SPL
• Sensitivity: 108 +/-3 dB SPL / 1 V rms / 1 kHz
• Transducer principle (headphones): dynamic, closed
• Weight w/o cable: 297 g
• Noise cancellation: Max 32 dB (passive)