The Blumlein stereo setup consists of two bi-directional microphones (the Blumlein Pair) placed at the same point (horizontally) and angled 90° to create the stereo image.
The Blumlein stereo setup is a coincidence stereo technique, which uses two bi-directional microphones (figure-of-eight) at the same point and angled at 90° to each other. The configuration is also known as the Blumlein Pair. This stereo technique normally gives the best results when used at shorter distances to the sound source, as bi-directional microphones use pressure gradient transducer technology and, therefore, is under the influence of the proximity effect. At larger distances these microphones lose the low frequencies.
The Blumlein stereo setup purely produces intensity-related stereo information. It has a higher channel separation than XY-stereo. The disadvantage is that sound sources located behind the stereo pair are also picked up and reproduced with inverted phase.
The English engineer Alan Dower Blumlein invented this principle and it was first described in a patent from 1931.