All headphones of the HD 500 series are working with the same electrodynamic transducer technology. Variants of the HD 500 series: HD 500A DO HD 555 HD 558 HD 559 HD 515 HD 518 HD 595 HD 598 HD 569 HD 598 SE HD 598 Cs HD 598SR HD 579 HD 599 HD 555 AQUA BLUE HD 595 MAGIC RED Older variants of the HD 500series: Angewandte Richtlinien und harmonisierte Normen: Applied directives and standards: The devices which are listed above comply with the following: Pos.No.