By Jonathan LippMicrophones turn sound waves into electrical waves. Selecting the right microphone depends on how you will use it. When used for recording, accuracy or response tailored for particular instruments is of primary importance. When used for live performance, ruggedness (reliability), immunity to feedback, and tailored response are more important.
Price and Quality
Price and quality generally go hand-in-hand, but many very good microphones are less expensive. Generally, what you get with a higher price is reliability, quality fit and finish, consistency (microphones of the same model are likely to sound the same as each other), consistent performance over time, repair-ability, smoother off-axis response (less likely to color the sound of other voices or instruments and less likely to cause feedback), and lower distortion and noise. And, of course, there is the pride of ownership in a finely crafted electro-mechanical object.
Digital Microphones
Digital microphones have the same features as analog microphones with an added interface for one of many digital standards such as AES/EBU, USB, Bluetooth, Lightning, Ethernet, or Dante®. Some may have both digital and analog outputs and even a headphone output. The advantage of digital microphones is that they are less prone to cable noise and interference, and some can be remote-controlled. Since the A/D (Analog to Digital) converter is built-in, it could be better or worse than the A/D built into your computer, phone, interface, or mixer. Once the signal is in the digital domain, you can’t do much to improve it. Remember, a good digital microphone will cost more than an equivalent analog microphone since it has added electronics. A cheap microphone is still a cheap microphone, even if it is digital.
Wireless Microphones
Wireless microphones are covered in another section but are normally used for live sound or video when a performer needs freedom of movement. As a note, wired microphones are more reliable with superior sound quality, and you should use them when wireless is not necessary.
Features and Specifications and Their Relevance
Pickup Patterns
Omnidirectional (Nondirectional) is the most basic and natural of patterns. The microphone will consistently pick up most frequencies at any angle, and there is very little notable difference in which way the microphone points. Omni microphones usually have only one opening for the sound entrance. Omni microphones are very good for hand-held news interviews, conference table pick-up, and any recording where isolation between microphones is less important than fidelity. Miniature versions can be directly mounted to instruments or attached to the body for hidden pick up of actors and speakers. Omni mics have no proximity effect and thus will sound the same at any distance.
Cardioid (Unidirectional or Heart Shaped) is a pattern that rejects sound from the rear of the microphone. Maximum pick-up is at the front (on-axis) with good pick-up around the sides. Cardioid microphones usually have additional openings in the housing to differentiate the direction of the sound. They reduce feedback in sound systems and are the most popular pattern for microphones used on vocals and instruments. Miniature versions are larger than Omni miniatures and are more finicky in placement than Omni. Most cardioid microphones have increased sensitivity to low frequencies (bass) when the sound source is close to the microphone (proximity effect or bass tilt). Variable-D and dual diaphragm microphones reduce the proximity effect.
Hypercardioid and Supercardioid microphones are similar to cardioid microphones, with more rejection at the sides but slightly more pickup at the rear. They are useful when ambient noise is high and feedback is a problem. They are much more sensitive to sound sources directly in the front than cardioids.
Bipolar (Figure-8 or BidDirectional) mic patterns pick up front and back (the back is out of phase) and have excellent rejection at the sides (almost total). Figure-8 is the natural pattern of a ribbon microphone and is optionally available on some dual diaphragm condenser microphones. It is usually used for recording or broadcast, occasionally for live sound. Its excellent cancellation at the sides is useful for total rejection of nearby sound sources, better than any form of cardioid microphone. Ribbons are known to rival condenser microphones in transient response and have a reputation for sounding natural on difficult instruments.
Boundary Layer (PZM, PCC, or Surface) microphones are used directly on surfaces like desktops, tables, walls, floors, or ceilings to increase clarity or reduce visual profile. When microphones are placed inches or feet from a surface, they pick up both the direct sound from the source and a time-delayed sound reflection from the surface. This reflection reduces the clarity of the sound (comb filtering). Placing the microphone directly on the surface makes the direct and reflected sound arrive simultaneously. Most boundary microphones use condenser technology and have omni or cardioid patterns.
Interference-Tube (Shotgun) microphones are often used in video production. They are usually mounted on a camera (news coverage) or suspended overhead with a boom pole or perambulator. These mics are primarily sensitive at the front, with secondary pick-up at the rear. Their frequency response is usually tailored for voice pick-up only. It is important that any ambient noise, including the breathing of a camera operator, be located at the side since there is some pick-up at the rear. Because they are meant to be used at a distance and will require a lot of amplification of distant sounds, windscreens and shock-mounts are popular accessories. Models are available with pattern control, and stereo models are also available. The full-sized models will have XLR connectors. The smaller ones for camcorders without XLR connectors may have 1/8" mini plugs and hot-shoe mounts.
Parabolic (dish) microphones are extremely directional microphones, often used at sporting events, surveillance, and nature sound recording. They only work for recording and broadcast and not sound reinforcement. Parabolic microphones consist of a parabolically shaped reflector dish with an omnidirectional microphone placed correctly at the nexus of sound reflections. The operator usually needs to wear headphones with a headphone amp to aim properly.
Noise-canceling microphones are used in high-noise environments like factories, vehicles, and communications, where clarity is more important than fidelity. Radio dispatch, mobile radio, intercom headsets, and paging are typical applications. Noise-canceling microphones are designed to pick up the voice with the lips touching or almost touching the microphone. Sounds farther away (even inches) are canceled out, including other people talking. Many cell phones have a noise-canceling mode for non-speakerphone use. Microphones are available in hand-held push-to-talk mics (PTT), gooseneck mics, and communications headsets.
Technology (Transducer, Capsule) Type
Dynamic (Magnetic) microphones generate their own signal as electromagnetic generators. They typically use a circular diaphragm attached to a copper coil surrounding a magnet, similar to a miniature loudspeaker. Some dynamic microphones have an impedance matching transformer built in, and fewer have an electronic amplifier built in that requires either battery or phantom power. Their simplicity makes them the most rugged of microphones. The weight of the copper coil on the diaphragm reduces the ability of the microphone to track very high frequencies, which is not a problem for most applications. Technically ribbon microphones are also “dynamic” since they are electromagnetic.
Ribbon microphones are also dynamic microphones in that the aluminum ribbon diaphragm is surrounded by a magnet, generating a signal. The low impedance of a ribbon requires either a transformer or electronic amplifier built into the microphone, which requires external phantom power. Because the aluminum ribbon is suspended in free space, it is easily damaged (stretched) by shock or wind. Some new designs use advanced materials to increase ruggedness. The natural pattern of ribbon microphones is Figure-8. Some ribbon microphones are available with cardioid and other patterns. The low mass of the ribbon gives it a transient response similar to a condenser without worrying about overload from high SPLs. Ribbons are known to smooth out harsh sounds.
Condenser (Capacitor, Electrostatic) mics use lightweight, low-inertia metalized membranes with superior capabilities to pick up high frequencies, reproduce detail, and exhibit low distortion. The principal of their operation requires them to use built-in amplifiers, which require batteries, external phantom power, or an AC power supply. The amplifiers in condenser microphones usually use solid-state transistorized electronics. Some classically designed (retro) models use vacuum tube electronics and usually require an external AC power supply for the tube electronics.
Large diaphragm models replicate vintage sounds, and small diaphragm models are more accurate. Almost all miniature microphones are condenser types. Traditionally, only studios used condensers due to their complexity and sensitivity to humidity. Modern condensers are vastly improved in ruggedness and immunity to humidity and are often used in the field.
Some condenser microphones are available as modular systems with a variety of interchangeable head capsules, amplifier modules, both rigid and flexible extenders, and mounting systems.
Most condenser microphone capsules are round in shape, but some are rectangular, triangular, and even ear-shaped. The round versions have more pronounced resonant peaks. The most common use of miniature rectangular capsules is in hearing aids, cell phones, and some lapel and instrument microphones.
Features
Shape (Form Factor) microphones vary in size from barely visible under 1/8" to large studio microphones. The two most popular shapes are cylinders with the element (transducer) at one end and connector at the other end and larger studio microphones that are either barrel cylinders (beer can sized) or side-address with a rotated diaphragm in a cage at the end of the housing. Other shapes include gooseneck (wand) podium microphones, lapel, hanging, through-surface, boundary (mouse) surface microphones, head microphones for performers, and push-to-talk microphones for mobile radios.
Single or Multipattern (Multidirectional, Polydirectional): Single pattern microphones have one of the patterns listed above. Multipattern microphones have two, three, four, or more variable patterns with a control to select which is in use. Modular microphones have interchangeable capsules to change the pattern.
Modularity: Some microphones have removable capsules (transducer elements), which you can change out for capsules with different patterns and features. Most of these are small-diaphragm cylindrical studio microphones. Some gooseneck and boundary microphones also have interchangeable capsules. Modular systems are not interchangeable between brands and systems. Other modular accessories include extensions between the body (preamp) and capsule, swivel joints, and screw-in attenuators. Some hand-held wireless microphones have interchangeable capsules.
Pad (Attenuator) is often found on condenser microphones. Any microphone that uses an internal amplifier is subject to overload. A pad is a switch that reduces the sensitivity of the microphone to prevent overload. You should only use the pad when needed since reduced sensitivity can increase noise.
Low-Cut (Bass Roll-Off) Filter reduces either proximity effect (popping, “p’s,” and plosives) or low-frequency noise. The amount of cut is either built-in permanently in the case of hand-held voice microphones or switched for multipurpose microphones. In the studio or on stage, eliminating bass sounds from non-bass microphones or other low-frequency room noises increases clarity and removes rumble.
Stereo, Surround, Binaural, VR (Virtual Reality), Ambient, Tetrahedral, and Ambisonic microphones use two or more microphone capsules to create two or more sound channels for ambient recording, VR, or broadcast. Some have a fixed pattern and positioning of the capsules. Others allow mechanical repositioning and electronic control of pattern and separation. Some multielement microphones allow recording the capsules separately, allowing you to manipulate the special effect after recording. Binaural microphones simulate the separation between the ears of a human head which creates a very realistic sound field when using headphones.
Connectors: Most professional microphones have built-in connectors that allow the cable to be unplugged. The most popular on modern microphones is the 3-pin XLR connector (male on the microphone, female on the cable at the microphone end). Exceptions include small microphones that do not have enough room for the XLR. These will either have a miniature connector on the mic or a built-in cable with a connector at the other end. This setup is typical of miniature microphones used for body pickup or attaching to instruments and also some boundary microphones. Stereo and surround microphones may have multiple or multipin connectors, and most vacuum tube microphones require larger multipin connectors to attach their specialized power supplies. Gooseneck (wand) podium microphones may have a built-in 3-pin XLR or a cable with an XLR at the end. Some professional microphones meant for paging, dispatch, and mobile radios have permanently attached cables with either specialized connectors or no attached connector at the cable end. Some boundary and surface microphones meant for permanent mounting are designed to have a permanent wire connected to them at the time of installation. Digital microphones may have XLR connectors if they follow the AES/EBU standard, a USB connector for direct to computer recording, lightning for direct to iPhone, or an ethernet RJ45 connector if ethernet or Dante compatible. Amateur microphones often have permanent non-serviceable cables attached and 1/4" phone or 1/8" mini connectors attached, which are not easy to extend without noise pickup.
Transformerless: Professional dynamic microphones are balanced by nature, but some have internal transformers for impedance matching. All condensers and some dynamic and ribbon microphones have internal booster amplifiers and traditionally have matching/balancing magnetic transformers at their output. Some have “transformerless” solid-state outputs, which eliminate the slight distortion and other effects caused by magnetic transformers. The disadvantage is that transformerless (really a non-magnetic electronic transformer) microphones are more prone to interference than magnetic transformers.
Handling Noise: There is no standard specification for this. Some microphones (including some very expensive studio microphones) have the microphone element (transducer) attached directly to the housing. This design can cause audible noise from any rubbing or other mechanical noise from handholding or through the mount or placement. The better hand-held microphones usually have some sort of elastic material between the element and the housing to reduce noise. Some microphones even have mechanical, acoustic, or electronic noise cancelation mechanisms to reduce noise further. Optional external elastic shock mounts are often used to reduce this noise.
Phantom and Battery Power: All condensers and some dynamic microphones have internal amplifiers that require power. Some microphones require power from internal batteries. Some will power from either battery or external power. Phantom power is external power delivered through the microphone cable to the microphone. Most mixers and professional camcorders have XLR phantom power, ranging from 9 volts to 48 volts. The microphones that require phantom power will not work unless the power is present on the microphone cable. Some microphones require 48 volts only. Many will accept any voltage from 9 to 48 volts. If there is no phantom power available from the mixer or camera, AC-powered and battery phantom adapters are available. Phantom power is compatible with dynamic microphones with balanced XLR connections, but it can damage unbalanced microphones. Some mixers and cameras have individual controls for each microphone channel to turn phantom power on and off. Some lower-end camcorders with 1/8" mini microphone jacks provide a special kind of external power for matching shotgun microphones. Check for compatibility. For digital microphones, the AES/EBU standard has phantom capability. USB is powered from the computer. And ethernet RJ45 connections require POE (Power Over Ethernet).
AB-Power, T-Power: There are also other external XLR cable powering schemes like “AB-Power” and “T-Power.” These are not compatible with dynamic microphones but are for specialized microphones primarily for film and high-end video production. Some mixers (primarily portable for video production) and some high-end cameras have the AB/T power as options, be careful because it can damage phantom or dynamic microphones.
RF Immunity: Many older microphone designs are sensitive to radio frequency emanations from cellphones. New designs for conferencing and public address eliminate RF sensitivity.
Specifications
Sensitivity is a rating of how much electrical power the microphone produces for a specific sound pressure level (SPL). Dynamic microphones are generally less sensitive than amplified (condenser and some other) microphones. High sensitivity is great for quiet sounds. Low sensitivity is good for loud sounds. High sensitivity combined with loud sounds can overload either the microphone’s internal amplifier or the device to which it’s attached. Low sensitivity with quiet sounds can lead to microphone noise and may not produce enough signal to drive the mixer or recorder. These issues are why some condenser microphones have a pad (attenuator) switch to adjust the microphone's sensitivity for properly matching it to the loudness of the sound.
Sound Pressure Level (SPL) is often expressed as “Maximum SPL” and is the amount of sound that will cause the microphone to distort the sound. Microphones with pad (attenuator) switches will have multiple maximum SPL ratings regarding the position of the switch. Dynamic microphones rarely specify maximum SPL since they can take almost any level.
Frequency Response: This specification can be misleading since it does not consider the purpose of the microphone. Human hearing extends from about 20Hz (cycles per second, Hertz) to 20kHz (kilohertz, a thousand cycles per second) for young ears. As we get older, we lose our very high-frequency sensitivity. Voices and specific instruments require different portions of the sound spectrum, and a wide frequency response is sometimes less desirable. The standards for publishing this rating can also be misleading and are not regulated.
Tailored Response: This is a type of inaccurate frequency response that purposely or accidentally compliments a particular type of sound (instrument, voice) in a way that enhances that sound’s clarity alone or in a mix. By reducing sensitivity for frequencies that are not essential to that sound, the pickup of other sounds nearby that are outside of that range is also reduced, enhancing the clarity and control of those sounds. Let’s use voice as an example. Too much bass response can produce popping sounds (plosives) or a muddy sound. Some voices have sibilance (painful "sss" sounds), and extended high-frequency response may make it worse. The chart above is a typical (desirable) vocal curve for a hand-held vocal microphone.
Noise, Self Noise (EIN, Equivalent Input Noise): This is a rating of how much electrical noise the microphone would make in a totally silent room (hiss). Dynamic microphones with no electronic amplifier (most of them) are as quiet as can be. Condenser microphones are the ones that make noise and are generally quieter as the price goes up. This is important, especially for use with quiet sounds, since the noise will be more apparent. In situations with loud sounds or when the microphone is close to the sound source, self-noise is hard to detect.
Applications
Vocal, Hand-Held Microphones are some of the most popular microphones, designed to fit comfortably in the hand and held close to the mouth. Most have cardioid, supercardioid, or hypercardioid patterns and have an enlarged capsule housing providing a built-in windscreen/pop filter. Optional foam pop filters can slip over the head for more protection. Higher quality models have reduced handling/shock noise, are more rugged, are more consistent in their sound signature, and are less prone to feedback. Most models are dynamic, but some have condenser capsules accommodating high SPL levels. Most hand-held vocal microphones have a tailored response that cuts low frequencies to compensate for the proximity effect caused by close-to-the-lips use, an upper midrange boost (between 8kHz and 10kHz) for clarity, and an above 10kHz cut to remove sibilance. This response matches most male vocalists well. Some models have a smoother mid/high response (less boost) which may favor female vocalists and males with high clarity in their voices. Most of the hand-held microphones include a stand clip for stand mounting.
General & Musical Instrument Microphones: Some dynamic instrument microphones are the same as hand-held vocal microphones without a built-in windscreen. When the vocal response happens to complement a particular instrument, these are appropriate. If not, they tend to make instruments sound harsh due to their boosted midrange and reduced bass response. There are a variety of cylinder-style condenser microphones designed for high SPL and usage close to the instrument. These condensers are moderately priced and much smoother in response than most dynamics available. Some flat-shaped side address microphones fit nicely in front of guitar amps. Music quality omnidirectional microphones (not the news interview types) have become popular when feedback or bleed from other sound sources is not a problem. Their neutral and accurate characteristics make fine recording mics. See other sections for direct injection (DI), re-amping devices, and instrument pickups.
Drum Microphones: These designs handle high SPLs and can take a beating if hit by sticks. For drums, the condensers mentioned above should be used for cymbals owing to their extended high-frequency response. They can also work on toms. For toms and snare, there are compact dynamic mics with a response tailored for drums that include built-in stand mounts and swivels that are easy to place in tight spaces. For the bass drum, there are often larger microphones designed for extended bass response. Some of the classic, larger, high-quality dynamic studio microphones happen to work well on drums. Their size is not a problem for the bass drum but might be a tight fit for the toms and snare. There are also miniature condenser microphones that can be attached directly to the drum rims without stands. We do not recommend miniature lapel microphones for instruments since their high sensitivity for voice pickup makes them prone to overload on instruments. There are also reversed, small loudspeaker microphones (very large diaphragm) specifically for the bass drum.
Brass Instruments are very loud at close range and can sound harsh if the microphone is overloaded. Ribbon microphones are excellent on brass, as are most dynamics that don’t have a mid-boost. Some miniature dynamic and condenser microphones are designed to attach directly to the instrument. But make sure that they can handle the high SPL if they’re a condenser. For the smoothest sound, avoid microphones with exaggerated high-frequency response.
Studio/Broadcast Voice/Announce, Podcasting: Most popular for studio work are large diaphragm condenser microphones, including the vacuum tube versions that are very forgiving when overloaded. Classic, high-quality large format dynamic microphones are favored in broadcast and some studio work. The Variable-D models have deep low-frequency response without proximity effect. The luxury of studio recording is that it is possible to place a vocal microphone farther away than on stage since feedback should not be an issue. This placement reduces popping and volume variations due to personal motion. When using condensers, if possible, a placement at eye level pointing towards the mouth eliminates the need for pop filters. If placed in front of the mouth, hoop-style pop filters are recommended. Some microphones have digital USB outputs which can connect directly to computers or mobile devices for podcasting and webcasting.
Orchestral Recording: Different techniques are used in recording orchestras or acoustic bands. Classic techniques include using a stereo microphone or pair at some distance from the orchestra to blend naturally and include room reverberation. Highlight microphones are often added for soloists. A more contemporary technique for motion picture soundtracks and popular tastes includes adding microphones to each orchestra section. However, use caution since getting too close to some instruments like violins can add harshness. Usually, condenser microphones are used due to their accuracy. Higher-quality ones will present less noise and higher consistency. We would not recommend condenser microphones designed for a close-in technique for popular music since these will be too noisy at a distance.
Conference, Teleconference, and Podium Microphones for recording, conferencing, and reinforcement are usually mounted or placed on tables or podiums. The gooseneck style can get the microphone closer to the speaker but is sensitive to natural body motion and popping if placed too close to the mouth. Boundary surface microphones are popular since they do not obscure sight lines and can add clarity. However, they are sensitive to noises on the table (tapping, shuffling), and some people do not recognize them as microphones and will cover them with paperwork. Specifying microphones with low RF sensitivity is very important since cellphones nearby can cause noise.
Field Reporter and Sportscaster: Omni microphones are usually used on-camera for news and sports or live radio broadcasting. Combination headphone and side-boom microphone headsets are popular with sportscasters since they do not restrict motion and allow them to hear the broadcast feed and cues. A broadcaster interviewing a person can either use a headset for their own audio and another mic for the interviewee or one mic which they move back and forth between them and the interviewee. Dynamic omnidirectional hand-held interview mics (rugged and immune to weather) are most popular in this application since interviewees are not professionals and often talk off-mic, and the omni is insensitive to off-mic talking. Cardioid and even shotgun mics have been used in very high noise environments but are much more finicky when positioned. Usually, interview microphones have a voice-tailored response for clarity and elimination of non-voice frequency sounds. Wireless versions of these microphones are being used more frequently but are prone to interference, especially at news events where many other newspeople may be using them in an uncoordinated method.
On-Camera Field News Shotgun Mics are often attached to the camera and will pick up ambient sound and speech when there is no way to place a microphone at the source. Even when it is possible to place a microphone at the source, the placed microphone is often recorded on one channel and the shotgun on the other for safety.
Sport and Event Ambient and Spot Pickup Microphones: Shotgun and parabolic reflector microphones are used for picking up field speech and audience/crowd ambience. The operator of a highly directional microphone usually needs a headphone monitor in order to accurately aim the microphone. For family events like weddings, a pass-around wireless hand-held microphone is often used by the videographer for table and group interviews and congratulations.
On-Set News-Casting Lapel Mounted Microphones (often wireless) are used because of their invisibility and because they move with the announcer. A sitting talent will often use a wired lapel for simplicity and reliability.
Video & Cinema applications have traditionally had microphones mounted (off-screen) above the actors on a boom or perambulator. Cardioid, hypercardioid, and shotgun microphones are used overhead. Today, more productions use hidden miniature omni condenser microphones with wireless transmitters to get the microphone closer to the actor and give more control over each actor’s sound.
Theater and Live Performance: Before the popularity of wireless microphones, a variety of techniques were used for live theater pick-up. Most recently, the go techniques were placing cardioid boundary microphones at the lip of the stage and hiding microphones in the set. These techniques still work, but contemporary tastes require the volume and individual control that individual body wireless mics provide on actors. Ultra-miniature condenser lapel-style microphones are placed in actors’ hair, over their ears, or in costumes as close to the mouth as possible. In popular musicals and song and dance reviews, head microphones, which move the microphone even closer to the mouth, can be used if their visibility is acceptable.
Dispatch and Facility Paging Microphones These microphones are in a variety of styles and often include push button switches for activation. Hand-held mobile-radio style, desk-stalk, and gooseneck types are used in stores, plants, radio dispatch, airports, and race tracks. Many have noise-canceling elements for high-noise environments. Most of them have permanently attached cables for a variety of connections.
Surveillance Microphones: Many security camera setups will also record audio along with the video. Some closed-circuit cameras have docking microphone options. Superior audio is possible with the microphone placed closer to the people being recorded. Microphones are made that resemble wall plate switches. And miniature microphones can be mounted to walls and ceilings.
By: Jonathan Lipp, Founder, Full Compass Systems
