Do you love listening to choirs and orchestral music? The recorded performances often sound amazing don’t they? The production quality of these recordings can make you feel as if you are present in the concert hall itself, enjoying the show. Curious to know how this effect is created? Then you need to find out what is a Decca Tree!
Recording big concert bands, choirs, and orchestras, can be quite the challenge for many sound engineers, even for the more experienced ones. Hence, I think it is important for budding audio practitioners to at least have a basic understanding of one of the most important recording techniques that is used in such situations!
Decca Tree – A Unique Technique
The Decca Tree is a spaced microphone array often used for orchestral recordings. Its design is similar to a stereo A–B recording method, but with a “center fill”. The first commercial use of the decca tree was in 1954 by Arthur Haddy and Roy Wallace. Improvements were then made by engineer Kenneth Wilkinson, and his team at Decca Records, in order to provide a stronger stereo image.
Here are the topics that we’ll be discussing:
- Setup requirements
- Microphones used
- Common applications
The Decca Tree requires three omnidirectional microphones to be arranged in a “T” pattern, and two more “outrigger” mics placed further to the left and right. The stem of the “T” faces the orchestra, with the centre mic placed 2.5 feet out and the ones on the crossbar are placed about 5 feet apart. Former Decca engineer John Pellowe had this to say about the specifics of the setup:
“…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…”
According to John’s description, the Decca Tree is usually about 3.2 metres high, with the centre microphone positioned roughly in line with the edge of the orchestra, pointing towards the centre of the strings section in front of the conductor. The two rear left and right mics (on the tree) would then be pointing towards the first violins and cellos (if that’s how the orchestra is arranged).
The two “outrigger” microphones would also be omnidirectional, and placed about twenty feet apart from each other, at the same height of 3.2 metres. They are often positioned about 5 feet away from the edge of the orchestra, looking down at the strings. Do also take note that the Decca Tree is fitted on a tall boom and suspended in the air, roughly above the conductor.
The microphones used in a Decca Tree have an omnidirectional polar pattern. The Neumann M-50 small-diaphragm tube condenser model, is a popular choice. In reality, the Neumann M-50s are not truly omnidirectional at the higher frequences, but exhibit some high frequency lift and directionality which will improve the stereo imaging quality of the Decca Tree technique.
Various other microphone methods such as X-Y, Mid/Side (M/S), or Blumlein positioning, have been used to replace the centre microphone. Other models such as the Neumann M49, Km 53, and KM 56 were also evaluated and utilised by the Decca team for early sessions. Later on, the Schoeps mk2S were used for live productions instead of the M-50, as it was more convenient.
It is well known that the Decca Tree is a stereo miking technique often used for large orchestras or choirs, but it can also be used to capture the “room sound” during recordings. For instance, when recording drums, its wide stereo image captures the nuances of the recording room better than most other techniques. However, in smaller rooms, the Decca Tree will not be as effective.
The Decca Tree can also be used for surround sound recordings. Ron Streicher, author of “The Decca Tree — It’s not just for stereo any more”, used a SoundField MK-V (four-element transducer) 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.
That’s all I have to share with you folks today. Have you seen the Decca Tree being used in a live performance before? Or maybe you’ve seen a different technique?
Let me know your thoughts down below and share this article with your friends!