Microphones – “Rules”

1. Microphones – “Rules” • Miking instruments is an art and a science • It takes knowledge, time, practice and dedication to develop the skills • Good Source + Good Placement + Good Mic = Good Sound • “Good” is subjective • Do not try to “Fix It In The Mix” • There are no rules, only guidelines

2. Microphones - Definitions • Sensitivity – output level of a microphone for a standardized signal input level; amount of amplification (gain) needed • Overload – highest sound level (dB) before microphone distortion occurs • Equivalent Noise Rating – internal noise of a microphone • Transient Response – how quickly a microphone responds to transients

3. Microphones - Dynamic • Limited and most erratic frequency response (mid-range emphasis) • Poor transient response • Less crisp, precise and transparent • Thicker sound with less detail • Resistant to overloading (high SPL ratings) • Rugged and reliable

4. Microphones – Condenser • Flattest and most extended frequency response • Excellent transient response • Detailed, crisp, clear and transparent • Easier to overload • More fragile • Requires phantom power or a power supply

5. Microphones – Large vs. Small Diaphragm Condensers • Small diaphragm • More accurate on-axis • Higher frequency response • Better transient response • More uniform directivity • Large diaphragm • More full and robust sound

6. Microphones - Ribbon • Wide frequency response • Smooth transient response • Warm and smooth sounding • Most are Figure 8 pattern • Easier to overload • Can be fragile and easily damaged especially by plosives or loud levels • May be damaged by phantom power

7. Microphones – Frequency Response Microphone response across a frequency range

8. Microphones – Frequency Response AKG C414 XL II AKG C414 XLS

9. Microphones – Frequency Response • On-axis • Response to sounds in front of the microphone • Usually the flattest frequency response • Off-axis • Response to sounds off to the side or behind the microphone • May be flat or erratic • Coloration of sounds • May degrade or enhance the overall sound

10. Microphones – Proximity Effect • Increase in low frequency response as the sound source gets closer to the microphone • Occurs at ~1 foot or closer (i.e., little to no proximity effect if mic is more than 1 foot away) • Most pronounced with cardioid pattern especially dynamic microphones • Least pronounced with omni pattern

11. Microphones - Patterns • Sensitivity and frequency response over a 360° circle • Common • Cardioid • Omni • Figure 8 (bidirectional) • Less Common • Hypercardioid • Supercardioid

12. Microphones - Cardioid • Full sound pickup from the front (on-axis) • Reduced sound pickup from the sides (~ 6 dB less) • Little pickup from the rear (15-25 dB less)

13. Microphones - Omni • Uniform sound pickup from all directions • Tends to be more directional at high frequencies(lower high frequencies off-axis)

14. Microphones – Figure 8 (Bidirectional) • Sound pickup at front and rear • Rejects sounds from the sides

15. Microphones – Pattern and Frequency Relationship Pattern changes with frequency http://www.neumann.com/?lang=en&id=current_microphones&cid=u87_data

16. Microphones - Close • Tight and present • Minimizes leakage or bleed • Excludes most of the acoustic environment • Level and phase cancellation can occur with multiple mics • Easier to return to the same sound if recording in a different room • Large differences in sound as mic distance is changed • Usually done with cardioid pattern microphones

17. Microphones – Distant or Ambient • Picks up a large portion of the sound source • Preserves more of the overall tonal balance • Room acoustical environment has a greater influence • Less dynamics • Can be mixed with close or accent mics (watch out for phase issues)

18. Microphones – Phase • Phase shift occurs when a sound source reaches two or more microphones at different times • Microphones being a different distance from the sound source • Certain frequencies will be out of phase resulting in a thin sound • Phasing is not always bad – can create interesting sounds • Combining out of phase signals into a single track can cause severe frequency peaks and dips or a very thin, washed out sound • Phasing is minimized when the two mics are at a 3:1 ratio or more from the sound source

19. Microphones – Phase

20. Stereo Microphones • Works well in capturing the tonality and spaciousness of many acoustic instruments • Improved sense of spaciousness and presence • May not be good for instruments with tight sound radiating patterns such as individual horns, flutes, woodwinds, electric guitar or low frequency instruments sounding better in mono such as bass • Usually a pair of the same microphones are used, but it is not required or used in all techniques

21. Stereo Microphones – Spaced Pair • Symmetrical along the centerline of the sound source • Each mic between 1/3-1/2 of the distance from the centerline to the edge of the sound source; mics can be angled in or out Sound Source D 1/3 – 1/2 D

22. Stereo Microphones – Spaced Pair • Excellent stereo imaging, but the center image can be indistinct or weak • Strong potential for phase problems • Recommended to follow the 3:1 rule • Check in mono for phase problems

23. Stereo Microphones – 3 to 1 Rule • Distance between the two microphones is 3 times or greater than the distance from the sound source Sound Source 1x 3x

24. Stereo Microphones – Coincident (XY) • Capsules are nearly touching • Midpoint of the mics is pointed at the center of the sound source • Angled inward at 90-135°

25. Stereo Microphones – Coincident (XY) • Stereo spread increases as the angle between the mics is increased • Stereo imaging is excellent and often better than spaced pair • Almost no phase problems • Tends to lack spaciousness (depth or air), thus may be slightly flat or dry

26. Stereo Microphones – Near Coincident • Angled outward at 90-135° • Midpoint of the mics are pointed at the center of the sound source

27. Stereo Microphones – Near Coincident • Stereo spread increases as the angle between the mics is increased • A greater sense of depth and air compared to coincident pair • Less phase problems than spaced pair

28. Stereo Microphones – Blumlein Pair • Two bidirectional mics are angled 180° apart (crossed Figure 8) • Offset by 90° so null points at the center of the sound source • Aligned on the same vertical plane (above and below)

29. Stereo Microphones – Blumlein Pair • Two bidirectional mics are angled 180° apart (crossed Figure 8) • Offset by 90° so null points at the center of the sound source

30. Stereo Microphones – Blumlein Pair • Pan one mic left and the other right • Excellent stereo imaging • Produces a very natural, open sound • Captures the overall reverberant character of a room, thus requires a good sounding room

31. Stereo Microphones – Mid-Side Pair • Center mic is usually a cardioid and pointed at the center of the sound source • Side mic is a Figure 8 and oriented 90° away from the center (pointing to the side) • Aligned on the same vertical plane (above and below)

32. Stereo Microphones – Mid-Side Pair • Center mic is usually a cardioid and pointed at the center of the sound source • Side mic is a Figure 8 and oriented 90° away from the center (pointing to the side) • Center mic picks up the direct sound and side mic picks up the room sound

33. Stereo Microphones – Mid-Side Pair • A sum and difference matrix is used, but can be done without one • Mid and side are recorded to separate tracks • Copy of the side track is made (two side tracks) • One side track is polarity flipped by 180° • One side track is panned right and the other left • Mid track is panned center • Both side tracks are added to the mid track; adding more side track increases the stereo spread and sense of openness • Complete mono compatibility

34. Line and Microphone Levels • Line level is a strong signal while mic level is weak in comparison (roughly 500-600 lower) • A line level device has a high output signal level and expects a high input signal level • A mic level device has a low output signal level and expects a low input signal level • Sending a mic level signal into a line level input results in a weak sound and noise due to the high signal amplification required • Sending a line level signal into a mic level input results in distortion • Instrument level is about 10 dB higher than mic level

35. Direct Boxes • Converts line and/instrument level to microphone and/or line level • Sound is clean and crisp and more present • Eliminates leakage • Often sterile sounding • Can be mixed with microphone signals of the same source

36. Direct Boxes • Active - requires power (battery, AC or phantom power) • Passive - does not require power; uses transformers • Passive direct boxes alter or color the signal more than an active direct boxes • Passive direct box are recommended for active sources (keyboards, guitars and basses with active pickups • Active direct boxes are recommended for passive sources (guitars and basses); piezo pickups tend to work better with active direct boxes • Direct boxes can be combined with microphones – watch out for phase issues

37. Direct Boxes – Typical Connections Instrument Direct box Instrument Level Mic or Line Level Mic or Line Level Instrument Direct box Instrument Level Instrument Level Amplifier “Thru”

38. Microphones • These are guidelines only • There are no hard rules or foolproof recipes • Use your ears • Use whatever serves the artistic and musical plan • “If it sounds good, it is good”