Named for Alan Blumlein (chief engineer at EMI in London during the 1930′s, and a pioneer in stereo audio), a Blumlein pair uses two coincident bi-directional (or figure 8) pattern microphones set up at 90 degrees to each other. This stereo miking technique provides a strong center image, and good room ambience. When using this technique, absolute polarity in the entire audio system is essential, mic distance from the source is critical in balancing ambience with direct sound, and since so much ambience is captured, a good sounding room is critical. (See also WFTD “Coincident“)