Ultrasone HFI-450 S-Logic Surround Sound Professional Closed-Back Headphones with Transport Bag S-Logic Natural Surround Sound Dynamic principle Frequency range 20-20.000 Hz Impedance 32 Ohm Sound pressure level 96 dB. Connectivity Technology: Wired Closed-back home & studio headphones S-Logic Natural Surround Sound Safer hearing Frequency range 20-20.000 Hz Impedance 32 Ohm