Although the binaural recording technique drifts in and out of fashion, it is nonetheless useful — placing a pair of mics either side of a baffle replicating the acoustic properties of the head can provide impressive three‑dimensional imaging for the headphone listener. Problems with this technique, including the effects of variations in listeners' ear shapes and the inability of speakers to directly reproduce the effects of the binaural encoding, don't stop the technique having valid uses in the studio.
The German company Soundman, manufacture several binaural recording systems, all using the recordist's head as a baffle, with miniature microphones placed in the ears like in‑ear Walkman headphones. I tried the OKM II with its A3 powering adapter. A slightly cheaper alternative (the 'Solo' model) is available without the powering adapter.
The OKM II is stored in a compact plastic case complete with a couple of spare colour‑coded foam capsule covers and a rotating cable tidy. The one‑metre 'Y' lead connecting the ear pieces is terminated in a gold‑plated 3.5mm TRS jack plug, suitable for most portable recorders — DAT, MiniDisc or even MP3. The omnidirectional electret capsules require the 'plug in power' normally available at the mic input sockets provided on such recorders.
The A3 powering adapter is a small plastic box which provides a greater powering voltage than is normally available from portable recorders, resulting in more headroom and a wider dynamic range. It also incorporates an amplifier to feed the signal to the line input of a recorder, which is usually much quieter than the microphone input. The A3 is powered by a 6V alkaline battery claimed to provide 100 hours continuous operation. The OKM's microphone signal is input through a 3.5mm socket and a short flying lead with another gold‑plated 3.5mm plug carrying the line output.
The OKM II provides a decent dynamic range, low noise and a wide bandwidth. I found the microphones sat in the ear comfortably enough and stayed there — most of the time, at least! Recording the output on a Sony TCD8 portable DAT recorder, I obtained excellent results with good imaging and little in the way of unwanted mechanical noises. However, care is needed to make sure the mic cables are not tugged during recordings and that the mics themselves are not exposed to excessive drafts or wind. If you like natural, spacious ambient recordings this is a very practical method capable of producing high quality results with minimal fuss.