Massdrop x AKG K7XX RED Edition Reference Open Back Headphones ————- Contents: Headphones, Cable, Manual, retail box. New Opened Box Condition. ————- Configured by Massdrop Manufactured by AKG Open-back construction Ruby Red (RAL 3003) colorway Preselected dynamic transducers Flat-wire voice coil Varimotion two-layer diaphragm Frequency response: 10-39,800 Hz Sensitivity: 105 dB/V Maximum input power: 200 mW Rated impedance: 62 ohm Genuine leather headband Memory foam earpads with velour covering Individually tested and numbered Detachable 9.