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It was originally developed as a sort of stereo A–B recording method adding a center fill. The technique was developed in the early 1950s and first commercially used in 1954 by Arthur Haddy, Roy Wallace, Kenneth Wilkinson, Stan Goodall, and their team at Decca Records, to provide a strong stereo image.
A Decca Tree setup includes 3 omnidirectional microphones in a "T" pattern. The stem of the T faces the orchestra, and the left and right microphones are placed about 6 feet apart. The third is placed 3 feet out and centered in front. To mix, the side microphones are panned hard left and right, and the output of the centre microphone is then sent to both left and right channels. The level of the centre microphone is set sufficient to fill in the centre "hole" left by the widely spaced outer microphones , but is not so high as to cause an overall mono sound to the recording.
The Decca Tree was originally used in orchestral situations, fitted on a tall boom and suspended high up in the air, roughly above the conductor. Three separate stands were sometimes used to set individual heights.
The technique traditionally uses three omnidirectional microphones, traditionally of the Neumann M-50 small-diaphragm pressure transducer tube condenser type, to record in stereo. These microphones are not truly omnidirectional at the higher frequences, but exhibit some high frequency lift and directionality which is likely to positively affect stereo imaging of the Decca Tree arrangement. Variations have been performed using a coincident pair, in X-Y, Mid/Side (M/S), or Blumlein positioning, in place of the center microphone. The Schoeps M 201 and Neumann KM 56 were also used by the Decca team.
The Decca Tree is a great sounding stereo miking technique often used in large orchestral or choir performances, but it can also be used as a room miking technique for recordings. When used for room miking drums, its wide stereo image captures the nuances of bigger environments better than most other techniques. In smaller rooms however, the Decca Tree does not work as well.
Ron Streicher, author of "The Decca Tree — It's not just for stereo any more" has also described methods for employing a Decca Tree for surround recording. He utilizes a SoundField MK-V for the center, a pair of Schoeps MK21 sub-cardioid condensers for the left and right, and a pair of Schoeps MK41 hypercardioid condensers for the left and right surrounds. The MK-V affords a number of possibilities to the Decca Tree, as it is a four-element transducer that can be decoded into 5.1 and 7.1 sound fields on its own, using the SoundField SP451.
- Decca Tree Recording with Georg Neumann pressure microphones M 50 - in German — pdf
- The Decca Tree — A classic microphone placement system of the 1950s
- The Decca Tree — It's not just for stereo any more — pdf
- A Decca Tree primer — Wes Dooley, Audio Engineering Associates AEA — pdf
- Stereo Bars and Decca Trees — Wes Dooley, Audio Engineering Associates AEA — pdf
- WikiRecording's Guide to Decca Tree Use and Setup