7.2 Microphone Types and Placement

Microphone types and placement are crucial elements in audio recording. From dynamic to condenser to ribbon mics, each has unique characteristics that shape sound capture. Understanding pickup patterns like cardioid and omnidirectional helps in selecting the right mic for different recording scenarios.

Proper mic placement is an art and science. It involves considering factors like the 3:1 rule for multi-mic setups and instrument-specific strategies. Mastering these techniques allows for capturing the best sound quality and creating the desired spatial representation in recordings.

Microphone Types and Pickup Patterns

Dynamic, Condenser, and Ribbon Microphones

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• Dynamic microphones convert sound waves into electrical signals through electromagnetic induction
  • Offer durability and suitability for high-volume sources (drums, guitar amplifiers)
  • Withstand high sound pressure levels without distortion
• Condenser microphones capture sound using an electrically-charged diaphragm and backplate
  • Provide high sensitivity and wide frequency response
  • Require phantom power for operation
• Ribbon microphones employ a thin metal ribbon suspended in a magnetic field
  • Produce warm, vintage sound quality
  • Exhibit natural figure-8 pickup pattern
  • Delicate construction requires careful handling

Microphone Pickup Patterns

• Cardioid pattern demonstrates heart-shaped sensitivity
  • Captures sound from the front while rejecting rear sounds
  • Useful for isolating individual instruments in multi-source environments
• Supercardioid and hypercardioid patterns offer narrower front pickup
  • Provide greater side rejection than cardioid
  • Small rear lobe of sensitivity
  • Ideal for noise rejection in live sound reinforcement
• Omnidirectional pattern captures sound equally from all directions
  • No proximity effect
  • Natural room sound capture
  • Suitable for recording ambient sounds or multiple sources
• Figure-8 pattern exhibits equal sensitivity at front and rear
  • Null points at the sides
  • Commonly found in ribbon microphones
  • Useful for stereo recording techniques (Blumlein pair)

Microphone Characteristics and Effects

• Polar patterns determine microphone sensitivity to sounds from different directions
  • Affect ability to isolate desired sources and reject unwanted noise
  • Critical for proper microphone selection and placement
• Proximity effect causes increase in low-frequency response as source moves closer
  • Characteristic of directional microphones (cardioid, supercardioid, hypercardioid)
  • Can be used creatively for fuller vocal sound
  • Requires careful management to avoid excessive bass buildup
• Off-axis coloration alters frequency response of sounds not directly on microphone's axis
  • Varies between microphone types and models
  • Can be utilized for tonal shaping or minimized through proper placement

Microphone Selection for Recording

Instrument-Specific Microphone Choices

• Dynamic microphones excel for recording loud sources
  • Ideal for drums (snare, toms)
  • Suitable for close-miking guitar amplifiers
  • Commonly used for live vocals (Shure SM58)
• Large-diaphragm condenser microphones preferred for studio vocal recordings
  • Capture detailed sound reproduction of acoustic instruments (piano, acoustic guitar)
  • Effective for ambient room miking
  • Examples include Neumann U87, AKG C414
• Small-diaphragm condenser microphones excel in capturing transients and high frequencies
  • Suitable for recording acoustic guitars, cymbals, and orchestral instruments
  • Often used as stereo pair for overhead drum miking
  • Popular models include Shure SM81, Neumann KM 184
• Ribbon microphones favored for smooth high-frequency response
  • Often used on brass instruments (trumpet, trombone)
  • Suitable for guitar cabinets for vintage tone
  • Effective as room microphones for natural ambience
  • Examples include Royer R-121, AEA R84

Specialized Microphone Applications

• Shotgun microphones essential for film and video production
  • Highly directional pickup pattern captures dialogue
  • Minimizes background noise in outdoor settings
  • Models like Sennheiser MKH 416 widely used in field recording
• Lavalier microphones crucial for inconspicuous placement
  • Used in interview settings for clear speech capture
  • Essential for theatrical performances and broadcast
  • Popular models include Countryman B3, DPA 4060
• Boundary microphones (PZM) effective for capturing room sound
  • Placed on flat surfaces to utilize sound pressure zone
  • Useful for conference rooms, theater stages
  • Examples include Crown PCC160, Shure MX395

Microphone Placement Techniques

Multi-Microphone Setups and Phase Considerations

• 3:1 rule minimizes phase issues in multi-microphone setups
  • Distance between microphones should be at least three times the distance from each microphone to its source
  • Helps maintain phase coherence and prevent comb filtering
  • Critical for drum kit miking and ensemble recordings
• X-Y stereo technique uses coincident pair of cardioid microphones
  • Microphones angled 90-135 degrees apart
  • Provides good mono compatibility and precise stereo imaging
  • Minimal phase issues due to coincident capsule placement
• ORTF stereo technique mimics human ear spacing
  • Two cardioid microphones spaced 17cm apart, angled 110 degrees
  • Offers natural stereo image with some sense of room ambience
  • Balances direct and ambient sound effectively

Instrument-Specific Placement Strategies

• Drum kit miking combines close and distant microphone techniques
  • Close microphones on individual drums (kick, snare, toms) capture attack and definition
  • Overhead microphones provide cymbal clarity and overall kit perspective
  • Room microphones add depth and ambient space to the recording
• Acoustic guitar miking often employs multiple microphone positions
  • Near the 12th fret captures balanced tone between body and strings
  • Over the sound hole emphasizes low-end resonance
  • Blending close and room microphones adds depth to the recording
• Piano recording techniques vary based on desired sound
  • Lid fully open with pair of microphones for classical recording
  • Close miking under the lid for pop/rock contexts
  • Room microphones add natural reverb and sense of space

Microphone Impact on Audio Quality

Frequency Response and Tonal Characteristics

• Microphone frequency response significantly affects recorded sound's tonal balance
  • Some microphones emphasize certain frequency ranges (presence boost in vocal mics)
  • Others aim for flat response for accurate reproduction
  • Understanding frequency response crucial for proper microphone selection
• Proximity effect can be used creatively to add warmth
  • Particularly effective for adding fullness to vocals
  • Requires careful management to avoid excessive low-end buildup
  • Can be minimized by increasing distance or using omnidirectional pattern

Stereo Imaging and Spatial Representation

• Stereo miking techniques impact width, depth, and accuracy of stereo image
  • Spaced pair technique provides wide stereo image with sense of space
  • Coincident techniques (X-Y, Blumlein) offer precise imaging and mono compatibility
  • Mid-Side (M-S) technique allows post-recording adjustment of stereo width
• Choice between close and distant miking affects perceived intimacy and space
  • Close miking emphasizes direct sound, creating dry and intimate sound
  • Distant miking captures more room ambience, adding natural reverb
  • Blending close and room microphones allows control over depth in mix

Technical Considerations and Signal Quality

• Transient response of microphone affects perceived clarity and attack
  • Particularly important for percussion and plucked string instruments
  • Condenser microphones generally offer faster transient response than dynamics
  • Ribbon microphones can smooth out harsh transients for pleasing sound
• Noise floor and sensitivity impact signal-to-noise ratio of recording
  • Critical when capturing quiet sources or distant ambient sounds
  • Low self-noise important for recording classical music or nature sounds
  • Higher output level can reduce need for preamp gain, potentially lowering overall noise