Featuring an internal surround reflector, the HD 558 audiophile headphones are able to generate an extended spatial sound field for a listening experience that immerses the wearer during music and movies. They are outfitted with Sennheiser's innovative E.A.R. technology which ensures accurate channeling of audio signals into your ears, as well as sophisticated Duofol diaphragms which reduce unwanted resonances to an absolute minimum.