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Microphone Pickup Patterns For Field Recording Interviews.
There is really no such thing as a perfect all purpose microphone. If you do interviews outdoors, especially in windy conditions, consider an Omnidirectional microphone for outdoor use plus one directional mic. If you find that you must use only one microphone for a wide range of recording jobs consider the AKG C535EB. It is a detailed, neural in tone and clean sounding hand held mic with a proven track record of reliability. Its robust construction plus an effective built in wind/pop filter, attenuator for loud sounds and a low cut filter to minimize windnoise and plosives make it hard to beat as a general purpose microphone. It can be used for interviews, music recording, FX/sampling and capturing ambient sounds.
A field recordist goal for an interview is to record the subject with the most natural, uncolored sound possible and to minimize extraneous sounds , i.e. sounds not emanating from the subject. These extraneous sounds are often referred to as off-axis sound. On-axis sound is the sound that is emanating from the direction the mic is pointing. Rejecting more off-axis sounds means you hear less of the background sounds from the interview space while the sound from the subject is more pronounced. In a noisy space this can result in hearing the subject more clearly. Shotgun microphones have the most off-axis rejection, they "hear" the smallest amount of area around the mic, primarily picking up sounds directly in front of the mic. Hypercardioid and Supercardioid microphones have less off axis rejection than shotguns. They "hear" a wider area than shotgun mics. That is they pickup more sound above, below and to the sides of where the mic is pointed. Cardioid microphones have much less off-axis rejection than Shotgun, Hypercardioid or Supercardioid mics. They pickup a hemispherical area that includes the space far above, below and to the sides of where the mic is pointed. Omnidirectional microphones essentially hear everything around them, they have virtually no off-axis rejection except at higher frequencies. Control of the amount of sound from the subject verses sound of the environment is controlled by the distance the mic is from the subject. Microphones that have a lot of off-axis rejection tend to be brighter, some can tend toward a shrill or harsh character. Microphones that have less off-axis rejection tend to have a more accurate tonal character and a more open or smooth overall sound quality. The amount of sound that will be picked up by a microphone is detailed in the microphone's specification as a graphic representation. This is the microphone's polar pattern.
Common sources of extraneous noises that are not a function of off-axis rejection are handling and wind noise as well as "plosives". Handling noise is a result of the diaphragm, the portion of a mic that converts the vibrations in the air to an electrical signal, picking up the vibrations caused by holding a mic. A mic designed to be hand held will have a shock mount built into the capsule to prevent this. Windnoise can be an issue for any directional mic when used outdoors. A windscreen or pop filter is needed when these mics are used outdoors. A high Pass Filter (HPF) or Low Cut Filter ( LC) will help reducing windnoise as well as handling noise but these are best addressed at the source and not with filtering. Plosives are the popping sounds produced by the sudden force of air from speaking too close to the mic. For close use a directional mic needs a pop filter and in some cases a HPF to reduce this distracting sound artifact.
Condenser mics generally provide a higher output signal level. This reduces the amount of noise from the microphone preamp as it amplifies both the desirable signal as well as the noise plus distortion of the electronics used to build the preamp. If you start off with a higher signal level you end up with a bigger difference between the sound you want and the noises and distortion you do not want, i.e. you hear less noise and better detail. This microphone characteristic is found in the microphone's specification and is listed as sensitivity. It is usually measured in Mv/PA where the bigger the number the higher the output the microphone produces for a given sound pressure level. All other things being equal, a higher output mic will produce lower noise in your recording. Condensers also have a lighter diaphragm that allows them to be more sensitive to the subtle vibrations in the air produced by the human voice (or any sound) and this gives them a more detailed sound.
Handheld condenser mics are pretty rugged and capable of taking the rigors of field use but a dynamic mic is even less likely to be damaged by rough handling. The downside is as dynamic mics have less output level, they tend to produce more hiss in recordings.
One basic Rule of Recording is that the recording cannot possibly produce better sound quality than the microphone is capable of delivering. Recording quality begins with the microphone. The other significant consideration is the mic preamp. Many preamps use chips and capacitors that have noise and distortion that is not low enough to produce high quality results. You want the difference between the microphone's signal and the residual noise of the preamp to be as great as possible. Interview microphones typically produce output levels down at -40dB to -55dB therefore you need microphone preamp noise and distortion to be as low as possible as the preamp amplifies both the desirable signal and the undesirable noise plus distortion.
- Long Shotgun microphones are typically most useful for recording sound in noisy environments or when you cannot place the microphone close to the source. Long shotguns typically have very good off axis rejection, that is they hear only what they are aimed at. A practical concern of using long shotguns is that they are physically very long. This makes them pretty much impossible to handle without a person who's only job is to position the microphone.
- Short Shotgun microphones are smaller versions of the long shotgun. Besides being physically smaller than a long shotgun, most short shotguns offer a somewhat wider pickup pattern which makes them easier on the journalist who has to both operated the gear and do the interview. The short shotgun is probably the most commonly used microphone in location sound recording but is best left to the experienced user for interviews.
- Supercardioid & Hypercardioid microphones have a pickup pattern between a cardioid and a shotgun. They have more off axis rejection than a cardioid but not as narrow a pickup pattern as a short shotgun. These have a more natural, open sound than the shotguns and are typically easier to use as they do not have to be pointed as precisely as a shotgun.
- Cardioid microphones have a hemispherical pickup pattern. The cardioid is more effective for picking up a larger group of speakers at one time. A Cardioid mic is also the easiest for a interviewer to use as it can remain stationary allowing the user to concentrate on the subject not the microphone. A cardioid microphone has very little pickup pattern directly behind the microphone but it does pickup sounds on the far sides of the microphone. An added benefit of all three cardioid types is they generally are physically shorter. This makes the microphone easier to use in tight spaces. A cardioid interview mic held between the interviewer and subject pointed up will do a good job of hearing both and eliminate the need to move the mic. Rapid microphone movement can be detectable and distracting.
- Omnidirectional Microphones have a spherical pickup pattern, that is the they pick up sounds equally well in any direction. This characteristic makes them relatively immune to windnoise and less susceptible to handling noise but also means they will hear every sound in the area. This makes them difficult to use indoors or in a noisy environment. Omnis are the most commonly used interview mic and the most natural sounding, that is they produce the least coloration or tonal alteration of the sound. The downside is they do a poor job of isolating the subject and so can produce noisy results indoors. Outdoors they are the pickup pattern of choice.
Oral History Recording
- Lavalier Microphones are the small clip on microphones seen on Talking Heads on Television. To do very good quality recordings of inexperienced speakers while seated, consider using a lav mic, like the AKG C417, Audio-Technica AT899 or my favorite the DPA 4060. A lav mic is best for seated interviews for 2 reasons. First the subject does not need to know how to "stay on mic" they can turn their heads, move around and generally be comfortable. The second is that as they are not seeing the mic, they quickly forget they are being recorded. The interview then becomes a one on one conversation with another person, something we are all comfortable with and for this reason you get better content. An added plus is as the mic is close to the speaker unwanted background noises are not as audible. Low cost lav mics are not only noisy but more susceptible to the sound of clothes moving so buy a professional qualify lav mic !
Recommended microphones :
- ENG / Interviews
Hand Held Condensers
UniDirectional : M-Audio Aries, Audio-Technica ATM710, AKG C535EB
Omnidirectional : Beyer MCE58 (Omnis are best in windy conditions)
HQ Hand Held Condensers :
UniDirectional : Neumann KMS105 NI, Schoeps CMH 641U
Hand Held Dynamics
UniDirectional : Shure Beta 58, Sennheiser MD 431
OmniDirectional : Shure VP64, AKG D230, EV 635N/D, AT804
Oral History
AKG C417 or LM3/CK32, Audio-Technica AT899 or MT830R, DPA 4060 w/DAD6001 P48 adapter
- Stereo Recording
Low Cost
Joe Meek JM27, Studio Projects C4 kit, Audio Technica AT825
Low Cost Nature/FX
AT 3031, Rode NT4
HQ Stereo / ENG / Studio / Nature / FX
AKG C480B/CK62 or CK69, Schoeps CMC64, DPA 4041-SP, Sennheiser MKH30 & MKH50 & MKH800 & ME64/K6 & ME62/K6
- Stereo Shotgun: Audio-Technica AT835ST, Neumann RSM 191
- Stereo Music Recording
Low Cost Musical Mics
Studio Projects C4 kit or LSD2, Rode NT4 or NT5 stereo pair, Peluso CEMC6, Beyer MC930
HQ Musical Mics
Schoeps MK2S & MK4 & MK41 w/CMC6U or as CCM series, Schoeps Sphere
DPA 4006-TL & 4011-TL & 4022 & 4026 & 4052
AKG C480B w/CK61 & CK62 & CK63 or C414B-XLII/ST or C451ST
Neumann KM184, TLM170R
Beyer MC930
- Binaural: Shure WL183, DPA 4060 w/DAD6001 P48 adapter, Neumann KU100
- Shotgun: AT 875R, AT 897, AKG C480b/CK69, Sennheiser ME66/K6 or MKH416 or MKH70, Neumann KMR 82, Schoeps CMIT5U
- Large Diaphragm Cardioid Studio (best for studio vocal sound)
Low Cost
Studio Projects B1 & B3 & C1 & C3, Audio Technica AT3035, Rode NT1-A & Broadcaster
HQ Large Diaphragm Cardioid Studio
Audio Technica AT4050, AKG C414 & Solid Tube, Neumann TLM103 & TLM193 & TLM170, DPA 4041-SP
- Head Worn for Analysis
AKG C555L
- Surround
Schoeps Double M/S
Ambisonics Horizontal B Format w/Schoeps WSR-DMS LU using 2 CCM8Ls and 1 CCM2L
DPA 5015 4015-TL Surround Kit or DPA 5006-11 4006-TL/4011-TL Surround Kit
Do I need internal microphones ?
The internal mics can sound surprisingly good but cannot replace a high grade external mic, the Sony PCM-D1 is the only exception. Some solo journalist on a tight budget or that need to minimize the gear they are carrying use them for interviews, secondary ambient sounds, note taking and the like with good results. They can be used to record some ambience before or after an interview to use in post production to enhance the interview. This can add interest and flavor to improve the listeners experience without the need for additional gear.
Built in microphones are also useful for impromptu recordings and can make the difference between capturing an unexpected event or missing it. For musicians they are nice for recording practice sessions or friends playing for fun. Recording these just for fun sessions can sometimes result in discovering new ways to play a familiar song ! There are many imaginative uses for built in microphones, just remember their limitations.
Stereo Recording Techniques
This is a review of the different techniques used to record ambient sounds
and Concerts in stereo. I will cover common configurations using two, three and four
microphones. All of these methods have produced satisfying results. The
sound source, recording environment, and the desired effect determine which
of these techniques should be used.
I hope that this enhances the quality of the recordings that you create. Please let me know if you have any further questions or if you feel that I may have overlooked an important aspect of live sound.
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