Microphones convert the sounds you hear into electrical signals that can be recorded onto tape or hard disk. Choosing the right mic for the job at hand is critically important to getting the sound you want on your final tracks. No amount of EQ, compression or reverb can change the subtle signature that each particular microphone leaves on your audio tracks.

So, how do you choose that perfect mic without first buying and auditioning everything on the market? A good first step would be to familiarize yourself with the basic microphone types:

The term "Omnidirectional" describes a type of microphone that picks up sound equally from all directions. Omni mics tend to have very good bass response, without the artificial low frequency boost provided by the 'proximity effect' of a typical cardioid mic (see below). Really good omnidirectional condenser mics are great at capturing a sense of 'open space' and 'air', which makes them the first choice for critical reproduction of acoustic instruments in good sounding acoustic spaces, such as symphonic orchestras, vocal choirs, pianos or string quartets in concert halls.

You can also use omnidirectional microphones to 'close-mic' an instrument or vocalist without worrying about the artificial bass boost caused by a directional mic's 'proximity effect'.

Some of the highest fidelity mics available are of the omnidirectional condenser type, such as mics from Schoeps, DPA (B&K) and Earthworks. A common use for dynamic omni mics is in TV and radio reporting (known as Electronic News Gathering or "ENG"), where you want to capture environmental sounds along with the reporter's voice.

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A "Cardioid" microphone is more sensitive to sounds directly in front of it than to sounds 90 degrees off to either side (when plotted on a graph the response pattern looks heart-shaped, hence the name). A mic with a cardioid pattern is even less sensitive to sounds directly behind it — in fact, cardioid mics practically cancel pickup of sounds emanating from directly behind the mic. This makes cardioid mics very useful for sound reinforcement (P.A.) and live recording use, as well as the most popular choice for use in the imperfect recording environment of most home studios. To use a cardioid mic, simply aim the mic at the instrument you want to record, and the rest of the stage sound will be at least somewhat quieter than the desired instrument's sound.

There are a couple of variations on the cardioid pick up pattern. Supercardioid and hypercardioid mics are less sensitive to 90 degree off-axis sources than plain cardioids, meaning that they will do a better job of rejecting sounds from off to the sides. However, hypercardioids do pick up some sound from directly behind the front of the mic, making them a little bit like a 'figure-eight' mic (see below).

Cardioid mics exhibit a characteristic called the 'proximity effect'. The closer a sound source is to a cardioid mic the more the mic will accentuate that sound source's bass frequency output. This can add richness and fullness to a singer's voice or to a saxophone's sound, but it can also muddy the sound of a guitar amp or acoustic bass. When miking from a distance, cardioid mics have a tendency to sound somewhat thin in the bass when compared to omnidirectional mics. For this reason, cardioid mics are usually used for close-miking (with the mic placed less than two feet from the sound source), while omnidirectional or figure-eight mics are usually used when miking from farther away.

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Figure-eight mics have the open sound and good bass response of omnidirectional mics, with the added advantage that they reject sounds coming from either side of the mic. Since figure-eights pick up sound equally well from directly in back and directly in front, care should be taken that you don't capture undesirable reflections from low ceilings or nearby walls. A good place to use a figure-eight pattern mic is when you need to cancel reflections from side walls in a narrow-ish room but you still want to capture a good sense of room ambience.

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Dynamic mics use a 'moving coil' to sense the changes in air pressure that make sound waves. The wire coil is connected to a thin diaphragm, and the whole assembly is suspended over a permanent magnet. When moving air hits the diaphragm it causes the coil to move over the magnet, which causes a process called electromagnetic induction to take place. This causes an AC voltage to be formed that is an electrical 'analogy' of the original sound. The electrical signal that appears at the mic's output is a more or less faithful reproduction of the original vibrations in air, only in fluctuating AC voltages instead of air pressure changes.

These are by far the most commonly used mics for P.A. and stage sound use. Dynamic microphones are typically very rugged and don't require a voltage source to work properly. Cardioid pattern, small diaphragm dynamic mics are most often used as handheld vocal mics (like the very common Shure SM-58) or as instrument mics (like the equally common Shure SM-57). There are many other similar dynamic mics from companies like Audix, Electro-Voice, Sennheiser and others.

The Shure SM57 (left) and the SM58 (right): These are the most commonly used small-diaphragm dynamic microphones.

While similar to their small diaphragm cousins, large diaphragm dynamic mics are typically used for very loud, bass-heavy instruments such as tom-toms, kick drums, and bass amp speakers. The larger diaphragm allows these mics to withstand higher Sound Pressure Levels (SPL's) with ease, which allows low-distortion reproduction of very loud instruments such as trumpets, trombones and electric guitar amplifiers. However, the larger diaphragm will also have a higher moving mass, which can limit the high frequency response and transient response of the mic.

Some popular large diaphragm dynamic mics are:

• Electro-Voice RE-20 - A favorite of radio announcers and a good mic for kick drums
• Shure SM-7 - Similar to the E-V RE-20
• Sennheiser MD-421 - Commonly used on tom-toms and hand percussion, but also works great on horns, kick drums and guitar amps.

The Shure SM7: A large-diaphragm dynamic microphone used for broadcasters and voice-overs, as well as for miking kick drums, brass and bass instruments.

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Condenser microphones capture sound using a conductive diaphragm with a capacitative charged plate behind it. The charge is supplied by a DC voltage source from a battery or from the 48 volt 'phantom power' supply present in most mixers and mic preamps. Air pressure changes meeting the conductive diaphragm cause it to move, which causes an analogous AC voltage to be formed in the charged plate. These tiny AC voltages are sent to a tiny preamp built into the microphone, which brings the signal level up to where it can drive a typical micrpphone preamp. The signal leaves the microphone through the cable and on to the microphone preamplifier stage of the mixer. Because the diaphragm of a condenser mic can be made very thin and light, condenser mics tend to be more accurate and 'faster' than dynamic mics, especially in the midrange and treble frequencies. However, condenser mics tend to be more physically delicate than dynamic mics, so they are more commonly used for studio recording than for live sound and P.A.

Since condenser mics need a tiny amplifier built into the mic casing (called the "head amp"), the quality of its electronics will influence the sound of the mic. Some condenser mics use a small vacuum-tube circuit for their head amp, along with an external power supply box for the electronics. This is what is referred to as a "tube mic."

Small diaphragm condenser mics have the best high frequency response and quickest transient response of all the commonly available microphone types. For this reason, these mics are most often used as drum set overhead mics (to faithfully capture cymbals and stick attacks), for acoustic stringed instruments like guitars and violins, and for percussion instruments like vibraphones, shakers, and marimbas. Another common use for small diaphragm condenser mics is as stereo pairs for ambient pickup of acoustic events in good sounding spaces. The one downside to small diaphragm condensers is that they tend to have more self-noise than other types of microphones.

Some popular small diaphragm condenser mics are:

• AKG C 451 - The "classic" small-diaphragm condenser mic. An old favorite on piano, acoustic guitar and as drum kit overheads.
• Neumann KM184 - A truly professional recording mic, used in the best studios.
• Earthworks QTC-1 - A newer professional mic with extremely accurate frequency and transient response.
• Shure SM-81 - Very flat frequency response; commonly used on acoustic guitars and as drum kit overheads.
• Audio Technica AT-3528 - A cardioid model that is sort of a 'poor man's KM-84'.
• AKG C 1000 S - A good all-around budget favorite.
• Oktava MC-012 - From Russia, this is another mic made to be similar to the KM-84 but for a lot less money.

The Neumann KM-180 series small diaphragm condenser microphones are highly regarded by recording professionals.

Since condenser mics are intrinsically more sensitive to higher frequencies, it's possible to combine the warmth and fullness of a large diaphragm with the high frequency detail typical of small diaphragm condenser mics into a single microphone. These large diaphragm condenser mics are the mainstay of recording studios everywhere, especially for recording vocals, pianos, horns and other acoustic instruments. Some older vacuum tube based large diaphragm condenser mics, such as the Neumann U47, U67 and AKG C12, are collector's items prized for their sonic warmth and smoothly accurate reproduction of aural details. The Neumann U87 (introduced in the mid-1960s) is an FET-amplified, large diaphragm mic that has become a modern classic.

Some popular large diaphragm condenser mics are:

• AKG C 414 B-ULS - An industry standard for overhead drum miking and general use; provides choice of cardioid, hypercardioid, omni, and figure-8 pickup patterns.
• Neumann U87 - The industry standard; provides choice of cardioid, hypercardioid, omni, and figure-8 pickup patterns.
• Neumann TLM 103 - A new, lower-priced version of the famous U87; cardioid only.
• AKG C 3000 B - A budget mic based on the design of the venerable C 414 B-ULS; cardioid only.
• Audio Technica AT-4033a - An early '90s design that proved to be a huge hit. Now that its price has been lowered, the AT-4033 is once again a great value. Cardioid pattern only; great on saxophones.

The Neumann U87 is the 'gold standard' of large diaphragm condenser microphones, used in major recording studios around the world.

A quick note about Chinese-manufactured large-diaphragm condenser mics:

A company in the People's Republic of China, 797 Audio, has been making copies of popular Western-made microphones for many years now. These are such obvious copies that international copyright law prohibits selling them in Europe and North America. However, several Western companies have been working with 797 Audio to have their own designs made in China and then sold in the West. Most of these mics look almost exactly like the Neumann U87 and are claimed to sound 'just like the real thing, but for a fraction of the cost' — the Nady SCM 900, Joe Meek JM47 Meekrophone and Marshall Electronics MXL 2001-P are good examples. Of course, there ain't no such thing as a free lunch. I own an MXL 2001-P, and while I think it is a good mic for $150, I'd say it sounds more like a caricature of a U87 than the real thing. The MXL 2001-P's proximity effect is not well controlled, so male voices come out with a 'woofiness' in the low end if you work the mic too close. The high frequencies are more 'sizzly' than 'silky,' but I wouldn't say that the MXL mic sounds bad. It just sounds like a good cheap mic with a 'scooped out' midrange response, sort of how a mic sold at your local Radio Shack might sound if it was designed to 'sound like a Neumann.' In the end, I would say that $150 is just a little too much for the MXL 2001-P, but for $100 it would be worth it for many people. (Note that the Nady SCM 900 looks identical, and both the Nady and Marshall mics have been dropping in price.) I would say that an MXL 2001-P certainly beats a Shure SM58 or SM57 for recording vocals, piano or acoustic guitar, but if you already own a CAD, RØDE, AKG or other inexpensive condenser mic, don't think that you're missing out on anything.

Bear in mind that not all mics made by 797 Audio sound 'cheap.' The slightly more expensive Marshall Electronics MXL 2003 sounds noticeably smoother than the MXL 2001-P, and reviewers are positively gushing over the Studio Projects C1, C3 and B1 microphones (designed in the USA, made in China).

There are some good-sounding Russian-made condenser microphones available for almost as low prices as the mics made by 797 Audio. The Oktava MC-219 is an old 'sleeper' favorite.

The above are my own opinions, so feel free to apply your own personal grain of salt. Some reviewers have written that the MXL 2001-P is an unbeatable bargain, while others (especially at ProRec.com) have lambasted almost every Chinese-made mic as shameless (and lousy-sounding) scams. As you can see, I've taken the middle ground.

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When a wafer-thin, small aluminum ribbon is suspended between two mounting points inside a strong magnetic field, you get a microphone that is extraordinarily sensitive to vibrations in air (sound). Ribbon mics can really capture the thump of a plucked acoustic bass or the subtle dynamics of jazz drums. Unfortunately, ribbon mics tend to be extraordinarily fragile—blow on the ribbon the wrong way and you can stretch it out beyond repair. Nevertheless, ribbon mics remain a favorite of recordists everywhere.

Some common ribbon microphones:

• RCA BX-44 and BX-77 - The original classics.
• Coles 4038 - The standard in modern ribbon mics.
• Beyerdynamic M-260 - A budget ribbon mic; hypercardioid only.
• Royer Labs R-121 - A new ribbon mic design that is getting a lot of attention.

The Coles 4038 (left) is the standard ribbon microphone used by the BBC for recording and broadcast. The Oktava ML-52 (right) is a new ribbon mic from Russia.

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By combining two cardioid condenser elements into one chassis, a single point stereo microphone can be made. The most common is the X-Y type, where the two cardioid elements are pointed away from each other at a 90 degree angle. Some stereo mics are of the Mid-Side (MS) type, using a combination of a forward-facing cardioid element with sideways-oriented figure-eight element, which allows for remotely controlled adjustment of the stereo image width.

Some common stereo mics:

• Audio Technica AT-825
• Shure VP-88
• Crown SASS

The Shure VP88 is a single-point stereo microphone commonly used for on-location recording.

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Recording the human singing or speaking voice presents some unique challenges. Most people prefer a heightened sense of 'presence' on voices, and will often also prefer a mild bass boost for added 'warmth'. As a result, most microphones meant for recording or amplifying vocals have a 'tailored' response characteristic.

• Handheld, dynamic vocal microphones are designed to be very sturdy and produce as little handling noise as possible. They are also designed with a very 'tight' cardioid or hyper-cardioid pick-up pattern, so that there is less 'bleed' from other instruments on the stage.
  • The standard mic of this type is the Shure SM58. It can withstand very rough treatment and has very good feedback rejection, making it perfect for daily use on stages where amplified rock/pop/r&b/jazz bands play. The SM58 has a specially-tailored response that reduces bass pickup from far away (minimizing 'booming' from the stage sound) but will boost the bass when the singer comes in close (creating a big, warm sound). The SM58 also has a substantial peak in its response from about 2kHz up to about 12kHz, which adds a pleasant 'sheen' and overall brightness to the sound. This helps vocals cut through a dense mix with clarity and intelligibility.
    

You can usually tell if a microphone is designed for live sound vocal use if it is equipped with a pop filter to protect the pickup from blasts of air and plosive sounds ("p", "b" and "k" sounds). The Shure SM58 pictured at left has a spherical, metal screen pop filter lined with foam rubber on the inside.

• Condenser Microphones for Recording Vocals – Large-diaphragm condenser microphones like the Neumann U87 or AKG C12 are typically used for recording vocals in recording studios. Like handheld stage mics, these microphones also have a presence peak and proximity effect tailored to enhance the sound of the vocalist. However, because these large-diaphragm condenser microphones are to be used in the more controlled environment of a recording studio, they can have 'wider' cardioid pick-up patterns, allowing for a more 'open' sound.
  • A recording engineer will pick his microphones like a musician picks his instrument — a 'darker' mic will help tame a high, shrill voice while a clearer, brighter sounding mic will help the vocal cut through a dense mix. There is no single 'best' microphone for all situations — only a palette of good microphones from which the recording engineer has to choose the right tool for the job at hand.
  • The standard large-diaphragm vocal mic is the Neumann U87, while some prefer the vacuum-tube based Neumann U47. These microphones have a distinctive upper-midrange to treble boost (presence boost) and a warm, rich bass-boost from proximity effect. Similar mics to the U47 and U87 are the AKG C12 and C 414 B-ULS, which have the crisper sound characteristic of AKG microphones in general (which some engineers love and others hate).
  • There are many less-expensive versions of these microphones on the market today. Here is a partial list:
    • RØDE NT1000
    • Audio Technica AT-4033a, AT-4047
    • AKG C2000S, C3000B
    • Marshall Electronics MXL-2001-P
    • Studio Projects B1 and C1
    • Oktava MC-219 and MC-319

When a condenser microphone is used to record a vocalist, the engineer will often hang a pop screen in between the vocalist and the microphone to keep loud 'p', 'b' and 'k' sounds from overloading the mic's pickup and spoiling a take.

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There are many different kinds of instruments, so different kinds of mics are used. When recording acoustic instruments for classical music, the signal from the microphone should be as faithful as possible to the original sound. However, instruments used in rock and pop music can be very loud and require a microphone that can withstand extremely high sound pressure levels without distorting. It is extremely difficult to make a microphone that is both sensitive enough to pick up the subtle nuances of a fine acoustic instrument while also being able to capture the brute force of a rock kick drum or a Marshall stack without overloading. Since there is no single 'best' microphone for all situations, it becomes necessary to choose the best tool for the job at hand.

• Dynamic Microphones for loud sounds such as rock drumset, guitar amplifiers and close-miking of brass instruments – There are a select few dynamic microphones that are both rugged and have a smooth sound suitable for recording high-decibel musical instruments. These microphones are typically more expensive than dynamic vocal mics (over $350) and do not work as well as condenser mics on instruments with complex high-frequency information. The Sennheisser 421 and 422 and Beyerdynamic M88 are among the most widely used dynamic instrument mics. The Electro-Voice RE-20 is also popular. The Shure SM57 is frequently used on snare drums, hand percussion (congas, bongos, timbales, etc.) and guitar amplifiers, but not usually for bass-heavy instruments like kick drum or electric bass. You will usually see dynamic microphones used for live stage performances, while condenser mics are more often used in the recording studio.
  
• Condenser Microphones for Recording Instruments - When a higher level of fidelity is required, especially in the recording studio, condenser microphones will often be used. Again, the type of microphone must be chosen to match the sonic characteristics of the source to be recorded.
  • Orchestral instruments and Ensembles – Acoustic stringed instruments and classical music ensembles will usually be recorded with sensitive condenser microphones with relatively flat frequency response. It's generally acknowledged that small-diaphragm condenser mics such as those from DPA, Schoeps and Earthworks provide the most accurate response, while some prefer the pleasant-sounding coloration of the large diaphragm Neumann M50 or similar.
  • Close-Miking of Individual Acoustic Instruments – When recording an individual brass, wind or reed instrument for a pop or jazz recording, a large diaphragm condenser microphone such as a Neumann U87 or AKG C 414 B-ULS will often be used. If recording a featured 'solo', the instrumentalist is treated similarly to a vocalist—the microphone may be chosen as much for its desirable colorations as for its clarity, warmth, headroom, lack of distortion, etc.
  • Miking Piano - Acoustic piano is treated in several different ways, depending on the style of music and the sound quality desired.
    • For solo piano or classical music, the piano is usually miked from a considerable distance, with careful attention paid to the quality of room acoustics and the degree to which the microphones pick up the ambient sound of the room compared to the more direct sound of the piano. Often an X-Y stereo pair of condenser mics will be used.
    • For rock, pop or jazz piano in a group, the piano will usually be miked much closer, often with the lid closed and the piano isolated from the room sound with sound-absorbing blankets. For a robust, rich sound choose large diaphragm condenser mics; for a brighter, clear sound choose small diaphragm condenser mics.

• Miking the Drum-Set - For rock and pop, the various pieces of the drumset are miked individually. This allows greater freedom in the mixdown phase to alter the sound to taste.
  • Snare Drum - The most common technique is to place a Shure SM57 so that it picks up the sound from the batter (top) head. Sometimes a second microphone is placed underneath the drum to pick up the sound of the snare wires. The output from this microphone may need to be reversed in polarity so as not to introduce phase cancellations with the signal from the top snare mic.
  • Kick Drum - Depending on the sound of the kick drum itself, a large diaphragm dynamic mic such as an E-V RE20 may be placed close to the center of the front head, or inside the drum (if the front head has a hole in it or has been removed). Experimentation with placement will be necessary to achieve the desired sound.
  • Cymbals - In most cases a stereo pair of condenser microphones will be placed at least two feet above the kit to capture the sound of the cymbals (and the overall sound of the drumset). Where it is desired to capture the sound of the tom-toms with the overhead mic pair, it is usually best to use large diaphragm condenser microphones for the task (the AKG C 414 B-ULS works well here). If the tom-toms will be close-miked, it is usually best to use small diaphragm condenser mics so that the low mids don't build up to an unusable degree. Suitable small diaphragm condenser mics include the AKG C1000S, Audio Technica AT-4041, Neumann KM-184 and Oktava MC012.
  • Tom-Toms - If desired, the individual tom-toms can be close-miked with large diaphragm dynamic microphones such as the Sennheisser 421. Small, clip-on condenser mics are also used (such as the Shure Beta 98). Take care to place the microphones so that they will not cause phase cancellations or introduce excessive 'bleed' between tracks.
  • The Old-Fashioned Way - In the 1950s and '60s, drumsets were often miked with only two microphones, one a couple of feet or so in front of the kit, the other a couple of feet overhead and pointed at the snare drum. Ribbon mics like the RCA BX-77 or Coles 4038 were often used, as well as the newer large diaphragm condenser mics like the Neumann U67. While you will not get a stereo spread with this setup, you can get a very accurate picture of the acoustic sound of the drumset. This can be a very effective technique for making live recordings of jazz groups.

If you are recording your parts one at a time, overdubbing track by track in order to build up your production, you may be able to get away with only one microphone. As you can tell from the information you've just read, there really isn't one microphone that will be best for all the instruments you may need to record, in addition to your vocals.

In order to make the decision easier, you will need to prioritize. Usually the vocal is the single most important element in the mix. Therefore, it's probably best to get a microphone that complements the vocals. Usually this will be a large-diaphragm condenser microphone (see Condenser Microphones, above). If you can afford a multi-pattern mic like the AKG C 414 B-ULS or the Neumann U87ai, you will have more flexibility in choosing the sound that best fits the source. However, a fairly neutral sounding cardioid-only condenser mic can work well on a wide variety of sound sources. Be sure to experiment with mic placement to get the best results.

When placing cardioid-patterned microphones on a stage or in the studio, remember the 4-to-1 rule—each microphone should be at least four times as far from the next one as it is from the sound source. For example, let's say you have a saxophone player and a vocalist standing next to eachother on a stage. Let's now assume that the vocalist will be singing up to six inches away from her microphone, and the saxophonist will be playing up to a foot away from his mic. Since the maximum distance between the sound source (the vocalist and the saxophonist) and their respective microphones will be one foot, the 4-to-1 rule dictates that the two microphones (and the two musicians) should be placed no less than four feet from eachother. Placing the microphones any closer together will likely result in excessive off-axis bleed from one mic to the other, resulting in nasty sounding comb-filter effects when you mix the sounds together. When using microphones with wider patterns, you will need to keep them further apart.

 

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