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Stereo Micing Techniques
Stereo Mics
28
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Professional
08/13/2012

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Term
When was the first stereo microphone technique introduced and where?
Definition
1881 at the Paris Opera House. It was called dual channel at the time and employed carbon microphones.
Term
In what year did condensor microphones come out?
Definition
1917
Term
In what year was the moving coil invented?
Definition
1931
Term
Who invented all the coincident mic techniques?
Definition
Alan Blumlein
Term
What is the minimum requirement for recording in stereo?
Definition
Same make and model microphones
Term
COINCIDENT
Definition
Distance and arrival times are the same
Term
What are the four distance variable?
Definition
1. Perceived Loudness
2. High Frequency Attenuation
3. Ratio of Direct to Reflected Energy
4. Time Differences
Term
Perceived Loudness
Definition
As a sound source comes closer, it is perceived louder, and as it moves farther away, we perceive attenuation.
Term
High Frequency Attenuation
Definition
The highs will attenuate before the lows do because they're weaker and can't travel as far.
Term
Ratio of Direct to Reflected Energy
Definition
The closer the sound source, the less reverb.
Term
Time Differences
Definition
Highs arrive sooner than the lows
Term
Why are orchestras set up the way they are?
Definition
Higher frequency instruments are placed closer to the front to allow the the weaker frequencies to reach the audience first. Instruments with more power in the lows are placed further back. This allows for a better blend of sound.
Term
XY Technique
Definition
Two unidirectional polar patterns with no space between the diaphragms (as close as possible without touching). The incident angle would be 90-130 degrees. The diaphragms must form an X.
-amazing mono compatibility
-of the three inter aural differences, it capitalizes on intensity
-sounds unrealistic
-good for TV since most TV is mono
Term
Blumlein Technique
Definition
Two bidirectional microphones with no space between them. The incident angle is 90 degrees fixed. This creates a four-leaf clover pattern. Because of the bidirectional patterns, you will get what's in the back left also in the right monitor and vice versa.
-widely used for live jazz recordings
-terrible mono compatibility but great in stereo due to long distance reflections coming back to the back of the mic.
Term
Middle Side
Definition
This technique calls for one unidirectional mic and one bidirectional mic. The unidirectional mic must be 0 degrees to the source. The bidirectional is 90 degrees off-axis. The uni faces the source, picking up the middle, while the bi picks up the sides. We must perform a middle-side matrix decoding in order to split the left/right signal. The positive side of the bidirectional mic must point left (on axis). The decoding is a 9 step process.
-has the best mono compatibility of all stereo techniques.
-if the source is too big, you'll lose some on the sides.
-widely popular for television broadcasts of audiences
-also used in the studio, just not on large sources
Term
Middle-Side Matrix Decoding
Definition
9 steps...
1. Mute Channel X (uni)
2. Pan Channel Y (bi) and Z(empty for now) hard left.
3. Bring Channel Y to Unity. Set Aux 1 to Unity.
4. You will send Channel Y to Channel Z, post fader!! Use Aux Send to Tie Line 1
5. You will invert the polarity of Channel Z (flip the phase). If the console doesn't have a polarity switch, you can use a phase inverted TT cable, XLR, or TRS cable. Bring the signal back in using Tie Line 2)
6. Bring up Channel Z until maximum cancellation. You should achieve maximum cancellation at unity.
7. Pan Channel Z hard right.
8. Un-mute Channel X
9. Mix between Channel X and Channel Y. NEVER TOUCH CHANNEL Z AGAIN!!!!
Term
NEAR COINCIDENT
Definition
We start introducing more space, but losing mono compatibility. Polar pattern of the mic, the distance between the two diaphragms of the mics, and the angle of the mic need to be taken into consideration. We can talk about the angles as individual or incident
Term
ORTF (Office of Radiodiffusion Television Francaise)
Definition
Two cardioid microphones with 7 inches of space between the two diaphragms (because the average human head is this wide), set at a hard fixed 110 incident angle (55 degrees off axis).
-better stereo imaging because we're using two inter aural differences: intensity and time.
Term
NOS (NederlandOmroep Sthichting)
Definition
Translates to Dutch Broadcasting System...Two cardioid microphones spaced 12 inches, 90 degrees fixed incident
-better depth perception, but worse mono compatibility because there's more space than ORTF technique.
Term
Faulkner
Definition
Tony Faulkner was a disciple of Blumlein. He liked the idea of two bidirectional mics, and came up with a new concept. He found himself recording in a long, narrow venue, and he didn't want early reflections coming from the sides, just front and back. Two bidirectional microphones, 8 inches of space, 180 degrees incident angle, 0 degrees to the source.
Term
BAFFLED TECHNIQUES
Definition
Also known as binaural.
Term
Dummy Head
Definition
There is only one perfect binaural technique: The Binaural Dummy Head. It responds to spectral, intensity and time differences. This technique is widely used for museum tours, video games, and audio books.
Term
SASS
Definition
Stands for Stereo Ambient Sampling System. This was a technique developed by Crown Microphone. Crown is popular for PZMs. Two PZM microphones are separated by a two inch block of foam, 360 degree incident angle, which means each microphone is 90 degrees off-axis. This will sound awesome when recording ambience in stereo.
Term
OSS
Definition
Stands for Optimal Stereo Signal. It was developed in 1986 by a Swiss engineer named Jureg Jecklin. He used the platter of a turntable, wrapped it in a lamb blanket, and hung it between two omnis. Two omnidirectional microphones separated by 7 inches of space and Jecklin disc. A Jecklin disc is an 11.81 inch diameter disc covered in lamb's wool. The two mics must be 0 degrees pointed to the center of the disc.
Term
AB
Definition
This technique was developed by Harvey Fletcher, and was used to record the orchestra for Fantasia. Two any polar pattern microphones as long as they're the same, separated by more than 12 inches of space, and then the 3-to-1 rule applies. If you're following the 3-to-1 rule and you're losing your center due to distance, sneak a third microphone in the middle.
-sounds the most realistic outside of the dummy head
-has the worse mono compatibility of all techniques
Term
Decca Tree
Definition
Decca Records was big in orchestral recordings. They came up with the Decca tree. There are two parts: the basic frame and rigger microphones. The basic frame of a decca tree is three omnidirectional microphones set up as an isosceles triangle, 12 feet in the air. The apex of the triangle is placed over the conductor's head. The base of the triangle is placed 2.25 feet behind the conductor, and they are separated by 4.5 feet of space. Rigger microphones, if applicable, are placed in-line with the base of the basic frame. Their positioning is one third the width of the room from the sidewalls. This technique is currently employed for surround sound recordings.
Term
What was the first stereo LP called?
Definition
Rail Dynamics, and it was recorded by an engineer called Emery Cook.
Term
What was the first surround recording, and when was it released?
Definition
The Empire Strikes Back in 1981.
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