Stereo Mic Techniques Flashcards by Hayley Roscoe

AB - preferred polar pattern

omni

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AB - mono compatibility

causes an unfocused center image

generally has poor mono compatibility

if pair is too far apart will cause a ‘hole in the middle’

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AB relies on ____ for localisation

relies on time difference of signals reaching each mic for localisation

distance between mics dictates time delay

time delay dicates sound source position in stereo field

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XY relies on ____ for localisation

XY relies on level difference of signals reaching each mic for localisation

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XY - mono compatibility

has a very solid centre of image

very mono compatible

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XY - qualities

produces sharp detailed images

narrower spread than other techniques

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spaced pair

2 x parallel omnis

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coincident pairs

blumlein

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blumlein

2 x bidirectional at 90 degrees, off axis facing centre of sound

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1 x cardioid

1 x bidirectional at 90 degrees

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2 x Cardioids at 90 degrees

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Near coincident pairs

ORTF

NOS
DIN

OSS/Jecklin Disk

Faulkner Array

Boundary Array

Dummy Head

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ORTF

2 x cardioids, 17 cm apart at 110 degrees

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NOS

2 x cardioids, 30 cm apart at 90 degrees

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DIN

2 x cardioids, 20 cm apart @ 90 degrees

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OSS (Jecklin Disk)

2 x omnis, 16.5 cm apart, separated by 28 cm diameter disk

Faulkner Array

2 x bidirectional, 20 cm apart, perpendicular to source

can be futher away for better balance and is effective at ear height

Boundary array

2 x omnis in boundary construction

dummy head

2x omnis, 6.5 inches apart

“in ear” of head to replicate how we would hear

standard listening environment

60 degress listening angle or sound field

different stereo setups give you independent control over what factors?

stereo recording angle

angular distortion

reverb distribution

ER localisation

positional information of a sound between two speakers provided by

level difference between L and R

time difference between L and R

combination of level and time difference

DEF:

SRA

Stereophonic Recording Angle

the space in the sound field in front of the mic system which will produce a virtual sound image between the loud speakers

and part of the sound source within the SRA will be reproduced between the speakers

any part of the sound outside the SRA will be preproduced at the speakers

angular distortion result from:

interaction between:

polar pattern

mic angle

distance between mics

major considerations for stereo zoom

angular distortion balance between direct sound and reverb

basica decca tree measurements

max of 274-320 cm high anything higher causes mics to act as ambient pickups and you'll need stop mics for direct sound A = B = C = 25.5" - 27" D = 36"

Decca tree positioning

basic triangle mounted so centre mic is 15-30cm in front of orchestra (measured from R leg of lead vln chair and L leg of lead cello chair) outriggers usually same hight as basic triangle L outrig in line with back of 2nd desk of 1st vln chair R outrig in line w/ back of 2nd desk cellos both outrig set back 142-158cm from orchestra

Where to point mics - decca tree

mic at eyes of 5'6" person L outrig - btwn chairs of Vln 1 desk, three rows back L triangle - btwn chair sof 2nd desk of Vln 1 Centre triangle - btwn chairs of 2nd desk Vln 2/Vlas R triangle - btwn chairs of 2nd desk of Cellos R outrig - btwn chairs of Cello desk, 3 rows back

listen for (decca tree set up)

centre of focus for L triangle (2nd desk of 1st vlns) centre of focus for R triangle (1st cellos) sense of depth field where 1st/3rd desks are also in focus, 4th/5th desks less focues

how do you know when your setup is too high or too low? (decca tree)

too low: hear individual desks, strings sound to dry and edgy, too much HF content instings (scratchy) too high: too much room not enough direct sound, feels far back in orchestra

gains and pans for decca tree - 3 mic setup

Left (0 dB / - inf) Centre (L: -3dB / R: -3dB) Right (-inf / 0 dB)

basic tree - 3 mic setup used for...

small orchestras

basic tree + 2 Out Riggers used for...

large orchestra

variation on basic tree + 2 outriggers

gains and pans for 5 mic LCR decca tree w/ outriggers

Left OR (0 / -inf) Left (L: -0.4 / R; -13.5) Centre (L: -3 / R: -3) Right (L: -13.5 / R: -0.4) Right OR (-inf / 0)

gains and pans for 4 mic decca tree w outriggers

Left OR (0 / -inf) L main (-0.9 / -8.5) R main (-8.5 / -0.9) Right OR (-inf / 0)

mics for decca tree

M50 (small diaphragm boundary mic, described as omni but is only really omni at low freq, HF shelf boost 5dB at 2kHz) any omni mics w/ similar high end boost Schoeps MK2H w/ 50mm sphere Shoeps MK2S (brighter) can use cardioid or wide cardioid for ORs Shoeps MK21 KM 84