The PROline 550 is designed as an improvement on the immensely popular HFI-550. Featuring the same 50mm mylar driver and loud, punchy sound, the PROline 550 also features detachable cables and speed switch earpads, and S-logic(tm) natural surround sound. The larger, circular earcups produce a sound that is wider and even richer than the HFI-550 along with great bass response and great isolation. S-Logic¿ Natural Surround Sound: S-logic¿ uses decentralized driver positioning to utilize the pinna of the ear in the manner it is used in everyday life, reflecting the audio signal off the surface of the outer ear in different directions before entering the auditory canal. This results in a very natural spacious three-dimensional sound. S-Logic¿ is the only headphone system which includes your entire sense of hearing. Safer Listening: Because the S-Logic¿ technology does not aim the auditory signal directly down the ear canal but at the pinna, pressure to the ear drum is decreased by up to 40% (3-4dB) for the same perceived loudness. This significantly reduces the risk of hearing damage and ear fatigue ¿ an absolute must if you spend a lot of time in headphones.ULE technology: The ULE technology was systematically developed by ULTRASONE for users who spend many hours in the headphones. All headphone drivers produce low-frequency magnetic fields. In response, ULTRASONE developed a special MU Metal shielding (ULE technology) to reduce the radiation by up to 98% compared to ordinary headphones. Tech Specs:Closed headphone,S-Logic¿ Surround Sound,Frequency range 10Hz- 22kHz,Impedance 64 Ohm,SPL102 dB,Driver 50mm mylar,Reduced Magnetic Emissions Standard,ULE Standard,2 yr warranty, www.ultrasoneusa.com.PROline box includes:Two detachable cables one coiled and one straight,Straight length 3m (approx. 9'),Coiled <3m with gold plated jacks.,6.3mm (1/4) to 3.5mm (1/8th) gold plated adapter included.,Spare pair of speed switch earpads,Demo CD,Carrying bag.