Ears-free headset Beyerdynamik NEM 192
E.g.
Intel Pentium III host with on-board ACI87 sound controller chip, pre-amplifier Beyerdynamik MV 100 set to +20dB
It is a good idea to identify the microphones prior to a recording, e.g. by tapping on each microphone in a predefined sequence. This is especially true if the microphones can be moved or their cables be detached.