Sony MDR-DS4000 Infrared Cordless Digital Surround Headphone System (Discontinued by Manufacturer) Real 5.1 channel digital surround sound system Digital infrared transmission for clear, dynamic sound Cordless headphones are comfortable and stylish Compatible with Dolby Digital, Dolby Pro Logic II, DTS, and MPEG-s AAC audio formats Neodymium magnets (360 kJ/m3) for powerful bass and clear treble sounds