Calrec Audio of Hebden Bridge in Yorkshire, have developed their SOUNDFIELD microphone over a number of years, based on the mathematical theory of sampling on the surface of a sphere developed by Michael Gerzon at the University of Oxford. Physically it is more than a microphone as such — it's a complex electronic control unit with the provision of linking the microphone part with up to 150 metres of multicore cable. The price of £2,600 should not be seen as anything other than representative of the superb beast it is...!

It has basically two areas of use — as a superb truly coincident stereo microphone with some unique features, or as a 4-dimensional Surround Sound microphone. The Surround Sound aspect should not be thought of as the disastrous quadraphonic sound of the early seventies. It is the microphone heart of the NRDC Ambisonics Surround Sound system which goes way beyond the achievements of the discredited quadraphonic era.

My temporary use of the Calrec Soundfield mic has been as a stereo microphone so I will mainly comment on this aspect. It was for a rather unusual line-up of four double basses.

There are four capacitor capsules in the microphone head with the usual low noise amplifiers in the body proper. The capsules are arranged uniquely in a tetrahedral form close together, contrasting dramatically with other attempts at coincidence. I am struck by the clarity of the stereo imaging due to the true coincidence (up to 10kHz) produced by this close positioning as well as the compensation facilities in the control unit's electronics, which provide a host of extras not normally available with stereo microphones. Opportunity is also taken in the electronics to create a wider and flatter frequency response and to improve the polar patterns over the frequency range (with further imaging improvements), apart from coincidence compensation.

A few stereo microphones feature remote control of the polar patterns. So does the Soundfield — from omni through to figure of eight. But additionally the angle of the capsules can be continuously adjusted between 0 degrees (i.e. mono) and 180 degrees at the control unit.

Further, suppose the microphone is not properly lined up for an orchestra or large group in a concert hall (and this can easily happen in slung situations) — no problem — an azimuth control allows a continuous 180° 'electronic' rotation! Suppose one needs the mic tilted up or down — no need to walk to it to mechanically move it — a control unit knob movement suffices. An amazing control is that for dominance — it gives the effect of moving the mic nearer to or further from the performers! Almost an uncanny feature.

But that's not all. If four channels are accurately recorded (the B format signals), then the whole of the above processing can be done subsequently on playback! So the balancer can keep his options open on azimuth, elevation, polar pattern, capsule angle and dominance. This way subsequent replay in ideal monitoring conditions can allow the correct decisions to be made.

The rest of the control unit deals with the Ambisonic monitoring or playback. PPM metering, level control and headphone monitoring are also included.

To sum up — a superb British microphone system with an unsurpassed versatility. With the return to simpler mic techniques (brought about incidentally by the revealing nature of digital recordings), there should be a great future for a system with more options than normal crossed pairs — especially when the use of these options can be delayed until later.

Calrec Audio Ltd manufacture and sell the Soundfield microphone under licence from the NRDC. A hire service for this system is also operated by Whitetower Records, (Contact Details).