A stereo audio headphone apparatus comprising a master headphone unit comprising a master housing, master circuitry comprising a stereo audio source and a wireless transmitter, a master audio output device for playing a first stereo audio channel, a master audio input device, and a first independently settable frequency equalizer for the first stereo audio channel carried by the master housing, and a slave headphone unit comprising a slave housing, slave circuitry comprising a wireless receiver, a slave audio output device for playing a second stereo audio channel, a slave audio input device, and a second independently settable frequency equalizer for the second stereo audio channel carried by the slave housing. The master and slave circuitries are operable in a pass-through mode with audio sensed by the master and slave audio input devices being delivered to the master and slave audio output devices via the first and second frequency equalizers.