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together to create one side of the stereo signal, and subtracts the side signal from the mid signal to create the other.The result is a very accurate translation of the stereo listening field. The presence of an
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M
Source
Note that | +S | |
that does not rely explicitly on a matched pair of |
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microphones. However, high quality microphones are | The | |
imperative for overall sonic integrity, as well as to ensure | ||
derives a stereo signal from a center mic | ||
that | coincident with a figure 8 | |
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mid does not have to be a cardioid. If more audience noise or reflections from the back of the room are desired, an omni could be used as the mid mic to great effect.The
cancels them out to leave only the mid or center signal.This process simultaneously minimizes side | ||
reflections that can yield confusion in a mono conversion. |
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Spaced Omni |
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The spaced omni technique is often used for recording |
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orchestras. It employs a matched pair of omni mics typically | Sound Source | |
positioned four to eight feet in front of the sound source. | ||
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The mics are normally at the same height as the |
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performers, although raising them to 10 feet or more in |
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the air can increase perceived ambience. The distance | D | |
between the mics should be approximately 1/3 to 1/2 the |
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width of the sound stage. While spaced omni provides | 2 3 | |
| D~ D |
excellent depth and stereo image, the center of the field can tend to be less distinct. In situations where there is too much unwanted background noise or the mics must be placed further away due to logistics, experiment with using carefully placed cardioids or supercardioids with this spaced mic technique.
As pointed out earlier, spaced miking techniques are not as technically accurate as some correlated miking techniques. They can be susceptible to phase anomalies owing to reflections entering the mics from various surfaces in the recording environmentalthough some people actually find this pleasing. Many engineers consider spaced mic techniques best for recording relatively uncorrelated sounds such as a pipe organ or outdoor ambience. Spaced techniques are also useful in creating
the surround channels for surround sound.
Decca Tree
Staff engineers at Decca
developed a technique known as thein England in the 1950s.This method and numerous variations are still very popular today in the recording of film scores.
Sound Source
conductor
A
1.5meters (59 inches) away at the bottom of the T. This structure is then mounted about eight to ten feet in the air and positioned so that the central mic is just behind the conductors head. The mics are tilted down at about 30
1.5 m
2 m
The Decca Tree technique is very
popular in film scoring
Choosing & Using Microphones | 23 |