The headphones are sensitive enough to be driven by portable music players such as a smartphone or tablet. 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 0.1%, an impedance of 20 ohms, an efficiency of 100 dB per 1 mW, and a total output SPL of over 130 dB when driven by 5 watts. The closed-back earcups are made from anodized aluminum rings with open-cell foam that's covered in leather-free. The Audeze LCD-XC are handmade in the USA.