Microphone Technique

1
Microphone Technique

• The Basics

2
Which Microphone

• Use a mic that produces the sound that is
  wanted.
  
• Keep in mind the two main characteristics of the
  mic -- one is frequency response.
  
• Most condenser mics have an extended upper
  frequency and provide a detailed sound.
  
• Dynamic mics have a good enough response for
  drums, horns, winds, and electric guitars.
  
• A mic with a presence peak (around 5kHz) adds
  more edge or punch.

3
Which Microphone

• Polar pattern affects leakage and ambience.
• The more leakage and ambience the more distant an
  instrument sounds.
  
• Omni mics pick up more of the room acoustics than
  directional mics when used at the same distance.
  
• The type of music/ensemble that is being recorded
  is a determining factor in deciding how many mics
  to use.
  
• Every instrument may be miked for a pop group.
• Two mics in a stereo configuration may be plenty
  for a wind ensemble or choir.
  

4
Distance from the Sound Source

• A few inches gives a tight, present sound,
  farther away gives a spacious, distant sound.
  
• An ambience mic is 10 feet away or farther.
• A boundary mic taped to the wall is a good
  choice.
  
• Classical music is usually recorded at 4 to 20
  feet away so that the mic picks up the sound of
  the hall.

5
Reducing Leakage

• Even if the drums are miked close and another
  instruments mic picks up the drums from a
  distance, it will add the sound of the distant
  drums in the mix.
• Mic each instrument closely -- the sound level is
  high and the gain on the mixer is low reducing
  leakage.
  
• Overdub each instrument one at a time.
• Record direct.
• Filter out frequencies above and below the range
  of each instrument.
  
• Use directional mics.
• Record in a large fairly dead studio --
  reflections from the walls are weaker.
  
• Put portable walls between the instruments.

6
Microphone Placement

• Dont put the mic too close.
• Different parts of the instruments give a
  different sound quality.
  
• A natural sound is achieved by placing the mic as
  far away from the instrument as the instrument is
  big.

7
Microphone Placement

• Once the distance has been selected, move the mic
  up, down, left, and right -- instruments radiate
  different tone qualities in different
  directions.
• Each position will give a different sound quality
  -- listen for the best sound.
  
• Or, close one ear, listening to the instrument
  with the other ear, and move around until finding
  a good sounding spot.
  

8
Microphone Placement

• Placing a mic next to the sound hole of an
  acoustic guitar gives a bassy, boomy sound -- use
  the bass rolloff.
  
• A saxophone projects highs from the bell, and
  mids and lows from the keys.
  
• A trumpet radiates strong highs directly out of
  the bell, but does not project them to the
  sides.
  
• A grand miked one foot over the strings sound
  natural under the sound board is bassy and dull
  and in the sound hole, constricted.
  

9
Microphone Placement

• If the mic must be placed close to a hard
  reflecting surface it will pick up an unnatural
  filtered tone quality.
  
• The reflected sound takes longer to reach the
  mic.
  
• Reflected and direct sound combine at the mic
  causing phase cancellations at various
  frequencies.
  
• This is called a comb-filtered effect and sounds
  like a flanger.
  
• Boundary mics will solve this problem.

10
Microphone Placement

• If each musician is being separately miked, and
  they are too close together, the sound will be
  blurred.
  
• Try to space the mics at least three times the
  mic-to-source distance.
  
• If the mics are one foot from the sound source,
  they should be at least 3 feet apart to prevent
  blurred, colored sound (phase cancellations).
  
• Or use two cardioid mics aimed in opposite
  directions.
  
• Be aware of off-axis coloration.
• Use a mic that has the same response over a wide
  area for an orchestra.

11
Stereo Mic Technique

• Stereo miking is the preferred method for
  recording classical music.
  
• Strive to get accurate localization of the
  instruments.
  
• If the mics are spaced or angled too close
  together it creates a narrow stage width.
  
• To far apart and it exaggerates the separation.
• Sit exactly between the monitors to judge.

12
Stereo Mic Technique

• A Coincident Pair is two directional mics with
  grilles touching, diaphragms one above the other,
  and angled apart.
  
• Two cardioids angled at 120 degrees apart.
• The greater the angling the greater the stereo
  spread.
  
• The coincident pair codes instrument positions
  into level differences -- like a pan pot.
  
• This method tends to reproduce a narrow stereo
  spread.

13
Stereo Mic Technique

• A Blumlein array uses two bidirectional mics
  angled 90 degrees apart and facing the left and
  right sides of the group.
  
• This method gives excellent localization.
• A Mid-Side technique employs a cardioid or omni
  facing the middle and a bidirectional facing to
  the sides.
  
• Stereo control is achieved by changing the levels
  between the mics.
  
• Boost the bass 4 dB in the L-R adds
  spaciousness.
  
• Coincident pair technique is mono-compatible.
• No phase cancellations because the sound reaches
  the mics at the same time.

14
Stereo Mic Technique

• A Spaced Pair is two identical mics several feet
  apart and aiming straight ahead.
  
• Omni is the most popular, but any pattern may be
  used.
  
• The greater the spacing between the mics the
  greater the stereo spread.
  
• May use a third mic if a greater spacing is
  needed.
  
• The spaced pair codes instrument positions into
  time differences.
  
• A sound on the left side reaches the left mic
  sooner than the right mic.
  
• This tends to make off-center sounds unfocused or
  hard to pinpoint.
  
• A good choice if the sonic images are to be
  diffuse or blended.
  
• May not be mono-compatible -- phase
  cancellations.
  

15
Stereo Mic Technique

• A Near-Coincident Pair is two directional mics
  with their grilles spaced a few inches apart
  horizontally.
  
• ORTF system is two cardioids angled at 110
  degrees and spread 7 inches.
  
• This method codes instrument positions into both
  level and time differences.
  
• May not be mono-compatible -- phase cancellations.

16
Stereo Mic Technique

• The Baffled Omni Pair uses two omni mics,
  ear-spaced, and separated by a hard or soft
  baffle.
  
• This method codes instrument positions into time
  differences at low frequencies and level
  differences at high frequencies.
  
• The baffle creates spectral differences -- a
  sound shadow of reduced high frequencies.
  
• A handy device is a stereo mic adapter or stereo
  bar.
  
• A Stereo Mic is a mic with two capsules in a
  single housing.