More about the B-Format "W" Reference and "Point Source"

Earlier we gave you the analogy of a listener standing between two trumpets. To fully describe to someone else the sound of the two trumpets, we needed to describe all three dimensions of the sound of each trumpet and the location of the two trumpets compared to where we were standing (the reference). The reference is a critical issue, for it establishes a single point from which all things are determined. Without that, relative position of the trumpets is unknown and a realistic image cannot be constructed.

When you set up a recording microphone on a stand, its capsule location within the microphone becomes the "reference" from where the audio originates. As long as there is only one microphone picking up audio, you have only one reference point and the microphone is a true single "point source". The minute we set up two microphones, we have two pick-up points, two references (two "W's") and we cease to have a "point source". Anytime you have two different pick-up locations of a single audio event, you introduce error if audio from those two locations is ever mixed together. In addition, as we have no central reference, we do not have a realistic image. Just like not being able to explain to someone else how the trumpets sounded without referring to your own position and the trumpets relative position.

With two microphones, the sound arrives at each microphone at a different time, and are therefore not phase coherent with each other. Unless the sound you are recording is very compact (like a single voice), and the two microphones are perfectly equidistant from the source, you will have problems staying free of phase cancellation and building a realistic image. Even with equidistant mike positioning, reflections from the environment can cause phase cancellation that impacts realism.

A choir or orchestra is a good example that invites error, as many would think to set-up 2, 3 or more microphones to record such as large source. The sound from one "end" of such a large source cannot be prevented from reaching a live microphone at the other "end". There could potentially be a significant distance between the two or three microphones. While this can be avoided by using a single mono microphone, it doesn't help us much when we want a realistic image. The ideal scenario for stereo imaging would be all microphones in the same exact location, (i.e. the same "reference point"), which we know is physically impossible.

Perhaps now you are seeing the value of SoundField single point source technology, and that only SoundField presents a "single point source" multi-capsule microphone system that delivers both stereo and surround. Single point source recording solves all kinds of phase related and imaging related problems in audio, for it includes a single reference. In stereo mode, a SoundField provides two microphones placed at the same exact location and in surround, five microphones or more.

In multi-channel, B-Format components X, Y, Z and W define just about everything we need to know about an acoustical event. Once we have this information, we can pull specific information from B-Format to define any number of points within the 3 dimensional B-Format sphere for an audio output. This means we can derive any kind of direction related information to yield any kind of multi-channel surround sound with precise localisation.