8 - Recording with two Microphones
Recording devices have two microphone inputs for stereo or twin channel recording which allows us to work in the field with a microphone in each hand. The arms, in effect, become microphone booms.
Why do it?
The purpose of two mic recording in the field is not to create a stereo recording but rather to ensure adequate coverage of a group of informants who may be moving around, talking to each other and to you - half a dozen children at play, for example.
Single mic problems
In circumstances involving several informants, a single mic will tend to give rather ‘hit-and-miss’ coverage: the audio will contain rather ugly half-captured exchanges as your mic attempts to ‘searchlight’ the elusive talkers. Some material will be missed altogether or be so off mic as to render it unusable. The single mic’s job is made even more difficult if there is sufficient background noise to demand closer micing.
Gathering the children together in a tight circle around the mic would be one solution but this will rob the scene of spontaneity and converts children at play into a static group.
Two mics also have their use with static groups where conversation is free flowing: a group of old mates around a large kitchen table, for example.
Be not afraid
Some field recording novices tend to avoid two mics; they consign the technique to the ‘too hard basket’ and claim that one mic is all they need. Long experience using both one and two mics and training others in their use, makes me certain that the single mic, while handling many situations adequately, will always be inferior to two mics. A single mic sets a limit on what is possible in the field.
Microphone noise or microphonics
The annoying rumble and knocking sounds which can intrude into field recording is commonly thought to be caused by the microphone leads moving and making contact with objects and clothing as you manipulate the mics (be it one or two). While movement of mic leads can contribute, in a small degree, to microphonics, the real culprit is hand and finger movement on the microphone barrel. If you have to change your grip, practise doing so without rubbing or tapping the barrel. During recording, it’s essential to keep your hand and fingers still, even though your arms may be manipulating the mics considerably. This does not mean you should clutch the mics tightly, which is tiring: a firm but comfortable grip is all that’s needed.
Practise
Two mics requires practise; manipulating them accurately will feel awkward at first. But with perseverance, it’s a technique which will reward the user with the confidence to handle just about any type of field recording.
Techy stuff
There have been suggestions from some technical people that two mics would cause phasing and signal cancellation. While I don’t have a technical ‘under-the-hood’ knowledge, I can say that no such problems have emerged since the technique first evolved over 30 years ago.
Stereo or mono?
And while on technical matters, in most audio editing applications it’s very simple – and desirable – to split your stereo recording into two mono streams. This allows any far-right–far-left audio, (caused by recording with mics far apart) to be adjusted or ‘panned’ nearer to the centre of the sound stage. Two mono streams also allow volume adjustment on each channel separately, which can help to compensate for any minor mistakes in mic position made in the course of field recording.
The future?
Radio New Zealand is broadcasts in mono, so twin mono production of programmes is appropriate. But, of course, the two mic technique, with judicious field recording and ‘panning’ of streams back in the studio, can give high quality stereo audio, should the future need arise.
