Decca trees

 A triangular array of omnidirectional microphones , a type of true spaced-microphone recording technique, where the central channel is distributed equally to left and right. This yields a very stable central image, avoiding the hole-in-the-middle which is problematic with many space-pair arrangements. A variant on the Decca tree places three cardioid microphones (L,C,R) in a triangle configuration. In all cases, the width of the tree is typically one-half to one-third the sound field width, and the center microphone is slightly closer to the performers. See binaural recording.