Decca Tree

The Decca Tree microphone system - or Decca Delta - is a type of stereo recording technique that has emerged empirically in the recordings and in 1954 Arthur Haddy, Kenneth Ernest Wilkinson and hosting teams tried.

General

The first real stereo recordings of Decca Records in London were published in 1958 by four producers and included 60 records. The Decca can look back on a long tradition in the exploration of specific methods in the field of recording technology. She also developed beyond her microphone recording method has its own stereo mixers, and other special recording equipment.

Producer and sound engineer James Lock ( Jimmy ) reported in the article by Jim Betteridge, " Keyed In To Opera ", Studio Sound, April 1987 concerning the necessary criteria that belong to a good recording. The descending order of importance as follows:

Development

The application of the three - microphone technique, which is called " Decca Tree " or " Decca Triangle" well known in the art, has evolved from the idea, from the minimum recording technique with only two microphones and multi - microphone technology to find a compromise in order to better bring out the clarity and depth stepping in opera and orchestral recordings.

The first " tree system " and also the first stereo mixer developed by Roy Wallace. The microphone triangle is approximately 3.00 m to 3.60 m (11 feet) above the stage level to the conductor around set up. This can be done using three separate microphone stands or with a bar structure. So the microphone system is not in front of the orchestra, as we see often, but more in the orchestra. Usually two boom microphones ( Outrigger ) be placed at the sides, up to about 2 /3 of the width of the stage are approximately in the middle between conductor and orchestra outer boundary. The Panpot the center microphone is on both stereo tracks into the center of the stereo recording. The left " triangle microphone " and the left " arm " panpotmäßig go fully to the left channel and the right mic and the right arm to go to the right channel.

As this technique is first tried in 1954 on a trial basis, the Neumann KM 56 microphones were used, which had a slope of 30 ° to the orchestra. Other Neumann microphones were tried, such as the M 49 in cardioid characteristic. The latter was a large diaphragm microphone. It also set up additional partitions between the microphones and tried the microphones with Kugelcharaktistik KM 53 and finally the ball microphones M 50 ( Special small diaphragm (! ) Pressure receiver on a 4 - cm - diameter golf ball large Plexiglas sphere ). It is repeatedly claimed that the M 50 are large diaphragm microphones, which is not correct. The membrane itself is " small".

The partitions that you initially once tried in the kidneys microphones M 49 trial consisted of four boards that were angled from a center outward so that each microphone in the middle of its 60 ° - " piece of cake " corner was positioned. Since the use of the M 50 - ball microphones but no more walls were used between the microphones.

The extra " boom " developed meaning that it also finally M 50 microphones were taken which show oblique or just above the orchestra. This microphone signals Enlarge the picture width and the sense of spaciousness of the stereo recording. Usually soloists need to be supported with additional microphones. Thus, the " Tree " arrangement for a long time remained generally unchanged, although the Decca engineers constantly minor changes to the miking made ​​, which always because of the space, orchestra and score differences can be expected.

Application

This type of recording technique, which can not be calculated physico- mathematical, was not observed for the same reasons by the scientific institutes acoustics - yes absolutely avoided. In a typical Decca recording session in addition every effort is made to find a suitable accommodation space for the composition and the cast who has the right reverberation characteristics. By hanging towels or by laying out large wooden panels on the cushioned seats in the concert hall the necessary quality of the reflected sound is further optimized.

Note: Unlike the fixed ORTF microphone system, the dimensions of the microphone system " Decca Tree " ( Decca triangle) are completely free. The offered to T- arrays with dimensions of 1.25 m and 0.7 m, and 2.50 m and 1.25 m are non-binding suggestions for Decca Tree and mostly too small. Each mixer aimed its dimensions individually own one, depending on the type of music, according to the size of the ensemble and by the room dimensions.

As a rule of thumb: The distances of the three microphones should never be less than each other a whole meter (3 feet ) to be. If the distance between the microphones less, there is in effect no more Decca triangle.

The imaginative surround sound microphone structure Atmos 5.1 ( with a front- microphone distance from each other by small 25 cm) is designated for promotional reasons completely falsely with Decca Delta. All other triangles with the 30 cm side length are nice small and practical, but make acoustically always be false and really have nothing to do with the idea of a Decca Delta.

When the Center more than 3 dB must be lower compared to the other microphones in the microphone level, then you can not agree to the microphone spacings something. This triple system is not case- AB- system with " auxiliary support " for the center. Especially since there is room -sound recordings, one does not go past the Decca Tree recording technique, even if this an accurate mathematical- acoustic calculation largely outside.