Documentation for Project #1 - Ambisonic Microphone

The Microphone:
An ambisonic microphone has 4 individual cardioid capsules in a tetrahedral frame. The output from each capsule is fed to a preamplifier. The raw output from the four preamps, known as "A-format", may be matrixed to a "B-format", also 4 signals: W=LFU+RFD+LBD+RBU (an omnidirectional sum), X=LFU+RFD-LBD-RBU (front/back figure-eight), Y=LFU-RFD+LBD-RBU (left/right figure-eight), and Z=LFU-RFD-LBD+RBU (up/down figure-eight).

The "front" of the microphone (horizontally and vertically) is approximately the mid-line of the centers of the LFU and RFD capsules. This assumes that all of the capsules are geometrically symmetrical.

The Preamplifier:
The signal from each capsule is fed to a high-gain, low-noise microphone preamplifier whose output has been calibrated to match the output of the other preamps for an equal acoustical pink-noise at each capsule. The output of the amplified B-format matrix is available at the output connectors of the preamp.

Ambisonic application:
A major advantage of recording in the A- or B-format is that the original recording may be reproduced in multiple formats (typically 1-32 channels) simply by changing the math, and at any time now or later. Computer programs and plugins allow easy manipulation of audio data, and the UHJ format allows playback in realtime on stereo systems (less the Z-axis).