AudioQuest Nighthawk

Compared to the drive-units commonly used in most headphones, NightHawk Carbon's 50mm dynamic driver much more closely resembles the high-quality drive-units found in today's most sophisticated loudspeakers—not simply in appearance, but, more importantly, in terms of function and performance. 
It employs a carefully constructed bio-cellulose diaphragm, voice-coil former, and compliant rubber surround, resulting in quality that is as easily seen as it is heard. Designed for exceedingly low distortion and high excursion with true pistonic motion, NightHawk’s driver contributes significantly to the headphones’ well-controlled bass, rich midrange, and naturally extended highs. Its combination of effortless clarity and outstanding representation of space produces meaningful, emotionally compelling listening experiences.

http://personal.audioquest.com/nighthawk