What is the 'Williams Tree'?

The 'Williams Tree' is basically a long overdue replacement for the 'Decca Tree'.

The idea for the Decca Tree started in the early days of Stereophonic Recording in the 1950s. Due to Angular Distortion (Geometric Distortion) of the reproduced stereo recordings, people came to the conclusion that there seemed to be a hole in the center of the stereo image. In fact it would have been better described as a spreading of the sound image in the center of the sound image. It was quite logical to introduce a third microphone pan-potted to the center (i.e. equal amounts of this third microphone sent to both left and right channels). In those days, this was a satisfactory solution to the problem.

When surround sound came along, the three microphones seemed a great solution for starting to build up the Front coverage of the surround sound image. It was unfortunate that nobody realized that there were in fact two seperate segments - one determined by the left and center microphone pair, the other by the center and right hand microphone pair. Surround in those days was even considered by some as just front and back segments, the side segments being neglected or rejected as unusable. However soon it was realized that a complete surround sound image was possible, by adding other microphones to cover the remaining part of the sound image.

But the Decca Tree remained the main front facing microphone system, it was also common practice to use omnidirectional microphones for each part of the Tree. In fact the Decca Tree actually produced two front segments, to the left, and to the right, but the actual coverage of each segment was very small - 10 or so. The left microphone was pan-potted to the left, the right microphone was pan-potted to the right, and the center remained in the center. In fact the Decca Tree was little better than a set of pan-potted omnidirectional microphones.

When the height revolution started, microphones were place above the Decca Tree but with no real analysis of the parameters needed to produce real segment reproduction - a really amateur appproach to trying to record the spacial aspects of sound.

The 'Williams Tree', which has been developed over a period of about 30 years, is a carefully constructed array of microphones covering each segment of the sound field, and producing a smooth and accurate natural sound image of the complete spacial image around us. This can be limited to only the upper hemisphere, or it can also cover the lower part of the sound image below the surround sound layer of microphones. The quality of the complete 3D sound image is infinitely superieure to the Decca Tree, and should become the standard approach to the recording and the reproduction of 3D Audio. However the recording array is only half the problem, in that equal attention must be given to the loudspeaker configuration, if optimum results are to be obtained. [Return to Home Page]