The Sennheiser HD 599 Special Edition open-back headphones feature an open-back design with velour ear pads for a natural and spacious sound. They have an impedance of 50 ohms and a frequency response of 12-38,500 Hz, making them suitable for a wide range of audio sources. The headphones have an ergonomic design with padded headband and ear cups for long-term comfort. They connect via two detachable cables - one with a 3.5mm plug and one with a 6.3mm plug. The Sennheiser HD 599 SE headphones provide detailed, natural sound reproduction for audiophiles.