The headphones are sensitive enough to be driven by portable music players such as iPods, iPhones, and other smartphones. Instead of utilizing traditional dynamic cone drivers, the headphones implement a neodymium planar magnetic transducer design to deliver a frequency response of 10 to 50 kHz with a THD of less than 1%, an impedance of 20 ohms, an efficiency of 103 dB per 1 mW, and a total output SPL of over 130 dB when driven by 5 watts. The headphone earcups are made of anodized aluminum with black, open-cell foam covered egg-based protein leather-free earpads. The Audeze LCD-X are handmade in the USA.