This technique is known for it's ability to produce a deep, wide and stable
stereo image is the Classic Blumlein using crossed figure of eight micro-
phones. Here the microphone polar pattern is a medium width forward and
backward lobe. The mics are setup so the lobes are at 90 degrees to each
One useful attribute of this method is that the rear lobes record
the rear 90 degree quadrant in phase, but out of polarity. This allows for
easy decoding of rear channel information. The side quadrants are recorded
out of phase, therefore placement is very important if you want to maintain a
proper direct to reverberant sound ratio and minimize strong out of phase
components when used indoors. Baffles behind the rear lobes in poor acoustic situations will allow you to achieve most of the open sound with excellent imaging while minimizing the negative effects of room problems behind the mics.
Typically this technique is best suited to wide rooms or outdoor recordings. This method produces very natural sounding stereo images but can suffer from limited bass response.
If you want to record nature sounds this technique produce results that are nothing short of amazing. With a high resolution 2 channel playback system properly setup it produces a 3D soundfield with very localized sounds behind the listener that is unbelievable until you experience it. This is the most like being there of any recording technique for nature soundscapes, very highly recommended.
When used with an Omnidirectional microphone it can be used for Ambisonics horizontal B format recordings. A simple matrix can be used to extract rear channel information to create 4 channel recording with 2 microphones.
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