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 as they have less trouble with wind. 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 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 results 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. The amount of sound from the subject verses sound of the environment when using an omnidirectional mic 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 area 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", i.e. popping sounds. 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 the 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 directional mics are used outdoors for this reason. A high Pass Filter (HPF) or Low Cut Filter (LC) will help reduce 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 the preamp amplifies both the desirable signal as well as the noise and distortion of 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. The microphone output level is found in the microphone's specification, it is listed as sensitivity. It is usually measured in Mv/PA. The the larger the number the higher the output level of the microphone. All other things being equal, a higher output mic will produce lower noise in your recordings. Condensers also have a lighter diaphragm that allows them to be more responsive 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 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 dynamic mics have less output level so 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. The greater the difference between the microphone's signal and the residual noise of the preamp the better the results will be. 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 to increase the difference between the signal and the noise. This is known as maximizing the signal to noise ratio, often listed as SN. Remember the preamp amplifies both the desirable signal and the undesirable noise plus distortion.
Basic Microphone types
- 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 sound pickup 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. In these situations they need to be very close to the sound source to produce clean results. 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 microphones worn by 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. Second, as the subject does not see 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 : CAD C-195, M-Audio Aries, Audio-Technica U873R or ATM710, AKG C535EB
Omnidirectional : Audio-Technica AT 8010, Beyer MCE58
HQ Hand Held Condensers :
UniDirectional : Schoeps CMH 641U, MicroTech Gefell M910
Hand Held Dynamics
UniDirectional : Shure Beta 58, Sennheiser MD 431
OmniDirectional : Shure VP64, AKG D230, EV 635N/D, AT804
AKG C417 or LM3/CK32, Audio-Technica AT899 or MT830R, DPA 4080, 4081 & 4060 w/DAD6001 P48 adapter
- Stereo Recording
Joe Meek JM27, Studio Projects C4 kit, AT4021, AT4022
Low Cost Nature/FX
AT4021, AT4041, AT4042 Rode NT4, Rode NT1-A, AT BP4025
HQ Stereo / ENG / Studio / Nature / FX
AKG C480B/CK62 or CK69, Beyer CK930 or MC900 series, Schoeps CMC64, DPA 4041-SP, Sennheiser MKH30 & MKH50 & MKH800 & ME64/K6 & ME62/K6
- Stereo Shotgun: Audio-Technica AT835ST, Audio-Technica BP4029(M-S), Sanken CSS-5, Neumann RSM 191
- Stereo Music Recording
Low Cost Musical Mics
Studio Projects C4 kit or LSD2, Rode NT4 or NT5 stereo pair
Mid Cost Musical Mics
AKG Blue Line or C451ST, Beyer MC900 series or CK930, Neumann KM184, Peluso CEMC6
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
Shure WL183, DPA 4060 w/DAD6001 P48 adapter, Neumann KU100
AT 875R, AT 897, Rode NTG-1, NTG-2, NTG-3, AKG C480b/CK69, Sennheiser ME66/K6 or MKH416 or MKH70 or MKH 8070, Neumann KMR 82, Schoeps CMIT5U
Camera mount shotgun
Rode Video Mi and Stereo Video mic, Sennheiser MKE 400
- Large Diaphragm Cardioid Studio (best for studio vocal sound)
AKG Perception 120, Perception 220 & Perception 420, 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
HQ Large Diaphragm HyperCardioid Studio
MicroTech Gefell M910
- Head Worn for Analysis
- Conference table recording
Shure MX392/3, AKG C547BL, Marantz Conference Grabber
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
PMD 620 Recommended microphones :
- ENG / Interviews
AT 804, AT 8033 , AT 8010, AKG C1000S
- Stereo Recording
Sony ECM-MS957, Audio Technica AT 822, Beyerdynamic MCE72, Rode NT4, Sennheiser MKE44-P
Audio-Technica AT 8035
AT Pro70, AT 803, ATR 35s (very low cost)
AT 803 w/8531 Power Supply, DPA 4060 w/MPS 6030 Power Supply
Home Made Binaurals
- Studio Quality Microphones
Schoeps CMBI or VST62IUg with MK series capsules
PMD 620 Recommended Microphone Cables :
1 foot XLR Female to 3.5MM right angle minjack male: Hosa XVM-101
5 foot XLR Female to 3.5MM right angle minjack male: Hosa XVM-105
Dual XLR Female to Male 3.5MM right angle minjack male: Hosa YXF-247
3.5MM stereo male to dual 3.5mm mono female Y adapter : Hosa YMM261
Hosa MIT-156 XLR to minijack transformer, mandatory with dynamic mics and a plus with battery powered XLR mics.
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.
How do I choose a microphone for nature or ambient 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. Condenser mics generally provide a higher output signal level and this is essential for recording ambient or nature sounds. 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. The microphone output level is found in the microphone's specification, it is listed as sensitivity. It is usually measured in Mv/PA. The the larger the number the higher the output level of the microphone. All other things being equal, a higher output mic will produce lower noise in your recording. The other specification to consider is Signal to Noise ratio, this is listed as SN. Again, the larger the number the lower the noise. Condenser microphones also have a lighter diaphragm that allows them to be more responsive to the subtle vibrations in the air produced by ambient or nature sounds and this gives them more clarity and detailed.
For isolating a single sound, like a specific insect, animal or bird, one of two options work best. First is the shotgun mic. They are highly directional and have very good off axis rejection, that is they hear only what they are aimed at. A high output, low noise, long shotgun does a very good job of isolating the sound you want from other sounds in the area. A short shotgun microphone is physically smaller than a long shotgun. Most short shotguns offer a somewhat wider pickup pattern which means they will pickup a bit more sound off axis. This can be useful if your target sound is on the move.
The Audio-Technica AT 875R is a great choice for a low cost high output, low noise mic as is the Sennheiser ME66. The Sennheiser MKH416 and Schoeps CMIT 5U are exceptional high quality shotgun mics. The Schoeps not only works well for typical shotgun applications but also has such a natural sound it works very well for samples, FX and even music.
A parabola is a dish shaped device that not only helps isolate a specific sound but provides some gain or amplification of that signal without adding noise. A well made parabola can be used with either a mono or stereo microphone. However, stereo performance with a parabola is very limited compared with a conventional stereo mic setup.
Telinga makes a very good parabolic reflector.
If your goal is to record a very natural sounding ambient space, a shotgun mic is not the right choice. For this type of recording there are 4 good options. One is using 2 small diaphragm omnidirectional mics mounted on a baffle (jecklin disc) or dummy head. This produces a realistic 3D sound when listening on headphones. The sound can be somewhat flat or lacking depth if played back on most stereo systems. The other three options do very well for playback on 2 speakers as well as headphones. An X-Y pattern using cardioids or figure of eight microphones works best. Without a doubt the most spacious and natural sound is obtained with the classic Blumlein or figure of eight stereo microphone technique. A 90 degree X-Y cardioid setup is close but is not as spacious nor does it render as much information behind the listener. The M-S technique is another option for doing nature or ambient recordings. This typically requires processing the signal with a matrix, either within the microphone or after the fact. For this reason, it may not produce as transparent a sound as a recording made with microphones that require no processing. If you have the choice, analog signal processing usually produces more realistic results. Doing the M-S decoding on a computer can sound harsh or result in reduced depth, 64 bit or higher processing is recommended. If stereo is decoded in the microphone, transformers are typically used and this results in very low output signal levels, a poor choice when recording soft sounds. Finding a good stereo microphone for recording ambient spaces is very helpful as it reduces the amount of gear you need to carry as well as simplifies setup.
The AKG C417 or DPA 4060 make great choices for binaural recordings while the Audio-Technica BP4025 or the Beyer Dynamic CK930 stereo pair are good choices for ambient and nature recordings. DPA, Schoeps and Sennheiser make a wide range of high output, low noise, high quality mics that work very well recording soft sounds.
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.