ESP950 Audiophiles seeking the best headphones money can buy should definitely consider the Koss ESP-950 electrostatic stereophone. These transducers operate on currentless electrostatic charges with push-pull capacitor plates to induce movement in an intervening, low-mass, semiconductive diaphragm. That's a technical way of saying that these ear pieces are highly sensitive and very responsive to minute fluctuations in audio, rendering your music with delicacy and warmth, and with microdynamics - tiny fluctuations in the musicians' output level -intact. Features: -Incorporates state-of-the-art electrostatic transducer technology. -Electrostatic element with a fast, low-mass diaphragm provides low distortion. -Includes electrostatic stereophone, energizer, battery pack, leather carrying case, connecting cables and 120V AC adapter. -Pivoting earcups and adjustable, detachable headband for comfort and convenience. -Includes electrostatic stereophone, energizer, battery pack, leather carrying case, connecting cables and 120V AC adapter. -Soft, vinyl closed ear cushion design for isolation. Specifications: -Frequency response: 8Hz-35kHz. -120V AC adapter.