This application is a continuation-in-part of U.S. patent application Ser. No. 11/428,057, filed Jun. 30, 2006 now U.S. Pat. No. 7,916,888. Headphones are sound reproduction devices worn on the listener's head. Equalization refers to electrical or physical means to modify the audible frequency response of the headphones to achieve a desired frequency response. Electrical equalization may be either active or passive. Active equalization uses complex circuitry such as integrated circuits that require an external power source. Passive equalization uses only simple circuit elements such as resistors, capacitors, and inductors, and does not require a separate power source.