Blumlein Array

A stereo microphone technique devised by Alan Blumlein in the early 1930s. It employs a pair of microphones with figure-eight polar patterns, mounted at 90 degrees to each other with the two diaphragms vertically aligned in so-called 'coincidence'. In this way, the signals from the two microphones differ only in their amplitudes (there can be no time-of-arrival or phase differences) in a way which accurately represents the angle of incidence of the sound sources.