Considered by many to be the world"s finest headphone, without regard to price, the HiFiMAN HE-6 features the company"s proprietary planar magnetic technology in a no-compromise design. With sensitivity of 83.5dB, the HE-6 must be paired with a headphone amplifier of comparable quality such as the HiFiMAN EF5 which delivers 2 watts per channel. The HE-6 is the reference choice of critical listeners around the world. HE-6 require a powerful headphone amplifier to drive it. Our EF6 headphone amplifier can serve 5 watt per channel at 50 Ohm. Specifications Freqency Response: 8 to 65 KHz Impedence: 50 Ohm Efficiency: 83.5 DB Weight: 502 g Accessories OCC(single crystal copper) 4pin XLR cable *1 (2 m / 6 ft) OCC XLR to 6.5mm headphone plug adapter *1 (1m / 3 ft) Headphone cable connector *2 Earpad for backup *1 Improved Leather earpads