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Stereo Recording Techniques “The trouble with real life is that theres no danger music.”
• What is Stereo? • Stereo miking is an• Stereophonic or ‘stereo’, is improvement over the reproduction of sound mono miking because... using two or more - Sense of soundfield, left to independent Audio channels. right position. - Depth and distance between• What is Stereo instruments. Recording? - Sense of distance between• Two microphones placed in listener. strategically chosen locations - Picture of acoustic relative to the sound source, both environment . recording simultaneously. - Accurate localization Channels will be similar, but each - The timbres of the will have distinct time-of-arrival instruments as heard by the and sound-pressure-level audience. information.
• Example of instrument placement e.g. orchestra or band Left and Right Speakers Poor Examples: • Here the instruments are Narrow sounding : accurately localized between the speakers. • Meaning sounds from the left of the ensemble come from the left speaker and sounds To spacious: from the right of the ensemble come from the right speaker.
Coincident Pair: (3 main types) Types of Stereo Recording: Microphones placed ‘close together’ and differences in loudness that create the stereo image, not time delay. 1. ‘X & Y’:• Two directional microphones, with Microphones Used: grilles almost touching and diaphragms - Normally Cardioid Polar Pattern angled apart, typically placed at 90° - Condenser apart. microphone,• A stereo effect is achieved through more detail. differences in sound pressure level between the two microphones. Because the sound arrives at both microphones almost together, the sonic characteristic of X-Y When to use: recordings has less sense of space and - Small choir, depth when compared to others. - Backing vocalists,• Sound in centre produce same signal in each - Solo acoustic guitar microphone.
AKG 414 and2. M-S (Middle and Audio Technica 4051 Side): Another Coincident method.• One directional microphone (Middle!), and one bidirectional (figure of 8) facing sideways Microphones Used: (side!), 90° off-axis. - Middle Cardioid Polar Pattern• Mono compatible, phase similarity - Side Figure of 8 Polar Pattern, so between the microphones. could be ribbon or condenser.The Method:• 1- Record directional on track 1 and When to use: bidirectional on track 2. -Lead vocals,• 2- Copy/Clone track 2 to track three, - Electric guitar, waveforms must be aligned. - Small choir• 3- Pan 2 hard-left and 3 hard-right.• 4- Reverse polarity!! of track 3.• 5- Group tracks 2 and 3 together.• 6- Balance al 3 tracks.
3. Blumlein Array:• Another Coincident method.• Developed for EMI Records in 1935 by Alan Blumlein.• Uses two bidirectional (figure 8) microphones angled at 90°• Can produced realistic image of Microphones Used: the sound, and the acoustics of - Middle Cardioid Polar the recording space. Pattern• Now common to buy hand-held - Side Figure of 8 Polar Pattern, so could be recorders that include the ribbon or mixed polar ability to record 360° with four pattern condenser. bidirectional microphones. When to use: Zoom H2, - Live Studio Recording, normally about £120. - Drums, - Piano
Near Coincident Pair or Microphones (ORTF): Used: - Pair of directional• Works on time and level differences microphones. arriving in each microphone. - Such as C414 shown• Sound from the right will take longer left to hit the left microphone focusing position of the sound.• It was devised around 1960 at the When to use: ‘Office de Radiodiffusion Télévision - Large sound-field, such as classical Française’, France. - Live recording of a band or group• Two directional microphones angled APART, about 110°.• Greater the angle, greater the stereo spread.• NOT Mono compatible (Different in time and stereo image).
Spaced Pair (A+B):• Two identical microphones placed apart, aiming straight ahead towards sound.• Stereo is created through mainly time differences (when the sound arrives at each microphone).• Positioning important!• Any Polar Pattern, but omni- directional is most popular (careful Microphones When to use: of background noise). used: - large choir or - Normally Pair of orchestra• ‘Decca Tree’, spaced pair with a omindirectional, - Drums, as well centre microphone for filling the can be others. as others. centre hole in of the image. • Brain decodes time differences into• Some phase cancellation is corresponding image locations. A delay of unavoidable, 1.2 millisecond is enough to shift an image all the way to one speaker.
Baffled – Omni Pair: Neumann - KU 100 - Dummy Head Mic.• Two omni-directional microphones, The KU 100 dummy head is a replica of the separated by a baffled (foam, wood, human head with a microphone built into each ear. Retail at about £7500!! balloon).• Very realistic Microphones used:• Stereo is created through time differences - Normally Pair of at low frequencies and level differences at omindirectional, high frequencies. can be others. Special not only for When to use: 1. Spacing of microphones creates time the microphones differences. used and how limited - Sampling, human 2. The baffled creates a sound shadow, to human observation of frequencies. But recording this reduces high frequencies for the millions were spent - Guitar/Strings microphone furthest from the sound on the shape of the source. ear!!
Recap Madness: Coincident Pair: 3 types: - X&YWhy use stereo recording? Two directional• 1. Sense of sound-field, (left to right microphones, with grilles position). almost touching.• 2. Depth and distance between instruments. - Middle and Side• 3. Sense of distance between One directional microphone (Middle!), and one listener. bidirectional (figure of 8) facing• 4. Picture of acoustic environment . sideways (side!), 90° off-axis.• 5. Accurate localization. -Blumlein Array• 6. The timbres of the instruments heard by the audience. Uses two bidirectional (figure 8) microphonesMust Remember! angled at 90°.Make sure the instruments are • Microphones placed ‘close accurately together’ and differences inlocalized between the speakers. loudness that create the stereo image, not time delay.
Near Cioncident Pair or (ORTF):• Works on time and level differences arriving in each microphone.• Sound from the right will take longer to hit the left microphone focusing position of the sound. Spaced Pair (A+B):• Two identical microphones placed apart, aiming straight ahead towards sound.• Stereo is created through mainly time differences (when the sound arrives at each microphone). Baffled – Omni Pair:• Two omin-directional microphones, separated by a baffled (fome, wood, balloon).• Stereo is created through time differences at low frequencies and level differences at high frequencies.
Further Reading and References:• Williams (2002) ‘The stereophonic zoom’.• Bartlett (2006) ‘STEREO MICROPHONE TECHNIQUES’.• www.recording-microphones.co.uk (GREAT!)• www.josephson.com• www.neumann.com• www.abbeyroad.co.uk (“Alan Blumlein - the man who invented stereo”)• www.news.bbc.co.uk (“Early stereo recordings restored”)