Decca tree

The Decca Tree is a spaced microphone array most commonly used for orchestral recording.

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, and later refined by engineer Kenneth Wilkinson, and his team at Decca Records, to provide a strong stereo image.

A Decca Tree setup uses five omnidirectional microphones, three arranged in a "T" pattern, and an outrigger pair further to the left and right. The stem of the T faces the orchestra, and the microphones on the crossbar of the T are placed about 5 feet apart. The centre microphone is placed 2.5 feet out. Former Decca engineer John Pellowe describes the specifics of the setup as follows:

Well we used to have a thing called a Decca tree which was an arrangement where [at] the front edge of an orchestra about 3.2 metres up in the sky you would have a centre microphone roughly in line with the edge of the orchestra, and then maybe 2.5 feet back and 5 feet apart you would have 2 more forming a triangle, omnidirectional microphones. These were Neumann [m50’s] I’m talking about...

The centre microphone would be looking right into the centre of the strings in front of the conductor. You would have the conductor out front, then there would be a couple of desks of strings before you get to the woodwinds, and we would be looking right into the centre of those strings with that microphone. Then we would have the [rear] two, the left and right [mics on the] tree, which would again be looking right into the first violins and the celli, if that was the way the orchestra was set out, and then we would have a couple of outriggers which were maybe twenty feet apart 3.2 metres high again, 10 foot 6, and they again would be omnidirectional... 5 feet away from the edge of the orchestra 10’6” high looking down into the strings. ... it was a very controversial method of recording, because when you have that many spaced omnidirectional microphones you lose a lot of the directional cues, which is absolutely right, the way that we would deal with that was we would pan the left and right tree half left and half right, and the outrigger mics we would pan hard left and right and we would paint an artificial stereo image... the reason we did this and consistently did it and got away with it and got wonderful reviews and many many awards was simply that the localisation cues were missing, but the sound was fantastic.

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