Two bi-directional microphones placed in the same point and angled 90° creating the stereo image.

The Blumlein stereo set-up is a coincidence stereo technique, which uses two bi-directional microphones in the same point and angled at 90° to each other. This stereo technique will normally give the best results when used at shorter distances to the sound source, as bi-directional microphones are using the pressure gradient transducer technology and therefore is under influence of the proximity effect. At larger distances these microphones therefore will loose the low frequencies. The Blumlein stereo is purely producing intensity related stereo information. It has a higher channel separation than the XY stereo, but has the disadvantage, that sound sources located behind the stereo pair also will be picked up and even be reproduced with inverted phase