Microphones

1. Microphones: Design and Application 2009 Created By: Brook Sutton

2. Introduction Microphone • ﬁrst device in the recording chain • A transducer - converts one form of energy into another

3. Microphone Designs THREE TYPES OF MICROPHONES Dynamic Ribbon Condenser

4. DYNAMIC MICROPHONES ELECTROMAGNETIC THE DYNAMIC MICROPHONE INDUCTION whenever an electrically conductive metal cuts across the flux lines of a magnetic field, a current of a specific magnitude and direction will be generated within the metal

5. DYNAMIC MICROPHONES ELECTROMAGNETIC THE DYNAMIC MICROPHONE INDUCTION whenever an electrically conductive metal cuts across the flux lines of a magnetic field, a current of a specific magnitude and direction will be generated within the metal

6. RIBBON MICROPHONES ELECTROMAGNETIC INDUCTION uses a corrugated thin aluminum diaphragm Very sensitive to sound pressure

7. RIBBON MICROPHONES ELECTROMAGNETIC INDUCTION uses a corrugated thin aluminum diaphragm Very sensitive to sound pressure

8. CONDENSER MICROPHONES ELECTROSTATIC PRINCIPLE consists of two very thin plates - one moveable - one stationary acts like a capacitor - varying changes in voltage will occur as the plate moves back and forth

9. CONDENSER MICROPHONES ELECTROSTATIC PRINCIPLE consists of two very thin plates - one moveable - one stationary acts like a capacitor - varying changes in voltage will occur as the plate moves back and forth

10. MICROPHONES CHARACTERISTICS AND RESPONSE PATTERNS

11. DIRECTIONAL RESPONSE SOUND SOURCE “On-Axis” Sound source angles directly into diaphragm

12. OMNIDIRECTIONAL 900 “polar pattern” show’s a mic’s sensitivity with o0 1800 respect to direction and frequency over 3600 2700

13. BIDIRECTIONAL 900 “ﬁgure eight pattern” pressure gradient - the pickup is 00 1800 responsive to relative differences in pressure between the front, back, and sides of the 2700 diaphragm

14. OTHER DIRECTIONAL PATTERNS CARDIOID PATTERN Cardioid means "heart-shaped", which is the type of pick-up pattern these mics use. Sound is picked up mostly from the front, but to a lesser extent the sides as well.

15. OTHER DIRECTIONAL PATTERNS HYPER-CARDIOID PATTERN This is exaggerated version of the cardioid pattern. It is very directional and eliminates most sound from the sides and rear.

16. MICROPHONES Frequency Response

17. FREQUENCY RESPONSE CURVE The on-axis frequency- response curve refers to the measurement of the microphones output over the audible frequency range. A microphone that is designed equally to all frequencies is said to exhibit a ﬂat frequency- response.

18. Rumble - high-level vibrations that occur at very low frequencies. (usually between 3 to 25 Hz) This phenomena can be avoided by using a “shock mount”, choosing a mic that restricts those frequencies, or by using a low frequency roll-off ﬁlter Proximity Effect - This effect causes an increase in bass response whenever a directional mic is brought within 1 foot of the sound source.

19. Transient Response - the measure of how quickly a mic’s diaphragm will react when it is hit by an acoustic wave. Sensitivity Rating - the output level that a microphone will produce - microphones with a higher sensitivity rating will produce stronger output signals Equivalent Noise Rating - a device’s electrical self-noise; often referred to as a hiss or hum Overload Distortion - caused by extreme SPL levels. Most microphones have a maximum of 140 dB. Many microphones employ a pad which reduces the microphones output thereby eliminating overload distortion. Impedence - output impedance is a rating used to match the output of one device to the input of another device.

20. BALANCED/UNBALANCED LINES Balanced lines use three wires to carry the audio signal: two carry the signal voltage (positive and negative), one acts as a shield or ground wire. Usually Low-Impedance devices use this connection. Two Types of Connectors: TRS -(Tip Ring Sleeve) XLR -also known as Three Pin Connector

21. BALANCED/UNBALANCED LINES Unbalanced lines use two wires to carry the audio signal: a single signal lead carries the positive, a seconded grounded shield completes the circuits return path. Used by high impedance and most line-level devices. Two Types of Connectors: TS -(Tip Sleeve) RCA - also known as a cinch plug or phono plug. Developed by the Radio Corporation of America in the 1940’s. Still in use today.

22. MICROPHONE PREAMPS Microphone Preamps are used to amplify the signal that comes from most microphones. Most studios employ a console that contains preamps for each channel. growing trend to stock outboard preamps to get a different sound from a microphone

27. PHANTOM POWER Some microphones require a DC voltage of +48V (volts) in order to operate. Most condenser microphones require a separate power supply either from a battery, console, or Phantom Power pack

33. MICROPHONES Techniques

34. FOUR FUNDAMENTAL STYLES OF MICROPHONE PLACEMENT FOUR TYPES OF MICROPHONE PLACEMENT: Distant Close Accent Ambient

35. DISTANT MIKING It considered distant miking when the sound source is 3ft or more from the microphone. Most often used to pickup large instrument ensembles, add a live, open feeling to a recorded sound

36. CLOSE MIKING It considered close miking when the sound source is 1 inch to 3 ft from the microphone. Used to record a desired sound when other sounds are present simultaneously

37. ACCENT MIKING It considered accent miking when the microphone is used to enhance presence and volume for a solo instrument(s) among an ensemble or orchestra. Often difficult to blend in with a natural balance in recordings.

38. AMBIENT MIKING It considered ambient miking when the reverberant room is more prominent than the direct sound source. Often used in stereo recording, audience, a hall where a performance is being held, or in the same room as a sound source to create a sense of space.

39. MICROPHONES Stereo Miking Techniques

40. STEREO MIKING TECHNIQUES Stereo Miking refers to the use of two microphones to produce a coherent stereo image. FOUR TECHNIQUES: Spaced Pair X/Y M/S Decca Tree

41. STEREO MIKING: SPACED PAIR Spaced Pair stereo miking refers to the use of two microphones placed in front of a sound source spaced anywhere from a few feet to 30 ft apart. In this conﬁguration there is a strong potential for phase discrepancies.

42. STEREO MIKING: SPACED PAIR Spaced Pair stereo miking refers to the use of two microphones placed in front of a sound source spaced anywhere from a few feet to 30 ft apart. In this conﬁguration there is a strong potential for phase discrepancies.

43. STEREO MIKING: X/Y X/Y - stereo miking refers to the use of two microphones of the same brand and model placed with their grills close together generally between 900 and 1350. Both microphones are set to pickup in a Cardioid polar pattern. (very common technique)

46. STEREO MIKING: M/S M/S- (mid-side) stereo miking utilizes two microphones with different polar patterns. Similar to X/Y with the exception that one microphone is set to a Bi- Directional polar pattern angled 90º toward the sound sources. The front microphone is set to a Cardioid polar pattern and is angled directly at the sound source.

49. STEREO MIKING: DECCA TREE DECCA TREE - this miking technique is primarily used in classical recording scenarios however it can also be used in studio situations. This technique employs three microphones set to Omnidirectional polar patterns. The left and right microphones are set 3 ft apart while the third mic is placed 1.5 ft centered in front of the left an right microphones.

Microphones

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