Choosing Microphones • Limited collection: useful for broad range of applications • Neumannn KM 184’s (desert island mic’s) • Small collection • Small diaphragm stereo pair of cardiod condensers (184’s) • Large diaphragm condenser (U87, KSM 44, AT 4050). • Standard dynamics (SM 57/58, Sennheiser 421) • Pair of omni’s, if not included above (higher costs) • Multiple polar patterns a real plus on a budget
Choosing Microphones (2) • Large collection of mic’s perceived to have specific individual applications. • Higher-end ribbon microphones • Tube condensers • Different types of vocal microphones • “Boutique” and Vintage microphones: Blue series, AKG C414, C12, U67
Microphone Placement / Working Distance • Distant • Close • (Accent) • Ambient
Distant Mic Placement • “3 ft or more” away from source. (often further) • Captures direct and reflected sound • Pro’s • Useful for picking up an ensemble • Natural tonal balance (at distance roughly equal to size of sound source) • Capture’s room acoustics naturally. • Con’s • Room acoustics must be good • Phase cancellation can be a problem
Close Microphone Placement • 1 inch to 3 feet • “present” sound quality • Excludes acoustic environment (isolation) • Tonal balance can be a problem • Instruments don’t radiate all frequencies in all directions • Leakage should be avoided • Physical distance between sources • Directional microphones • Gobo (acoustic barrier) • 3:1 distance rule: Nearby mic’s should be three times the distance from a particular mic as that particular mic is from its sound source.
Ambient Microphone Placement • Large distance from source - reverberant signal more prominent than direct. • Control over natural reverb level in stereo or surround applications • Audience reaction • Natural room acoustics
Stereo Miking Techniques • The use of two (or more) microphones to obtain a coherent stereo image. • Coincident; Near Coincident; Spaced • Coincident yields excellent stereo image (individual placement of sound sources). • Spaced yields a more spacious-sounding result. • Near Coincident techniques attempt a compromise. • Five main techniques: • Spaced Pair • X/Y • ORTF • M/S • Decca tree
Spaced Pair • Two mic’s (same make and model), placed in front of an instrument/ensemble. • Spacing ranges from a couple of feet to over 30 feet. • Typically, omni pickup pattern is used. • Interaural time and interaural amplitude cues create stereo image. • Potential for phase problems, especially when mixed to mono.
X/Y • Two directional microphones (same make and model) placed as close together as possible without touching. (coincident technique) • Generally at angle of 90° to 135°. • Midpoint faces towards middle of source. • Directionally comes entirely from amplitude differences. • No phase problems. • Cardiod or bi-directional • Bidirectional gives the “Blumlein” pattern, which can yield excellent ambient results.
ORTF • Near coincident technique. • Two directional microphones (same…), symmetrically angled outwards at 110°, about 17 cm apart. • simulates physical ear placement • Combines directional amplitude differences and interaural arrival time differences. • Best when used at a distance from ensemble. • Named after French National Broadcasting Organization. (Office of Radiodiffusion—Television Française)
M/S • Mid-side technique, using a cardiod pattern pointed at the sound source, and a bi-directional microphone oriented towards the sides (90° and 270°) • The mid pickup captures the source, while the side pickup captures ambience. • Offers excellent control of source-to-ambient balance, even after recording. • Excellent source pickup for chamber music. • No phase problems when mixed to mono. (coincident) • Requires a decoder/transformer matrix: • Software decoder, or • The side pickup is sent to two channels, with the phase reversed on one channel. • M + S = X ; M - S = Y
Decca Tree • A near-coincident technique, developed for stereo recordings of orchestras. • Typically, two microphones spaced about 1 meter apart. Center microphone about 0.5 meter in front of other microphones. • Omni pickups typically used, but variations possible. (Neumann M50’s is the classic choice.) • Outer mic’s panned hard L and R; Center microphone panned center, but with lower level. • Tree placed above and behind the conductor of an orchestra.