What Microphone Do I Get?
by Jeff Towne

It's one of the most common questions floating around radio-oriented mail lists, discussion boards, and any time radio producers get within six feet of one another.

If you're in the mood for some details to get you started, here's some info to help narrow the search.

There are lots of different kinds of microphone types: dynamic, condenser, ribbon, boundary, binaural, M-S and more. There are a myriad of pick-up patterns, different-sized diaphragms, variations in frequency response, sensitivity, self-noise, susceptibility to handling noise, wind or plosives. The possibilities can boggle the mind.

Basically, they are all devices to convert sound pressure levels into an electrical current. Dynamic mics' diaphragms move a coil of wire near a magnet, much like a small speaker in reverse. (In fact, if you wire a speaker, or a pair of headphones, into a microphone input, either will perform as a microphone--not a very good one, but either will act as a transducer from sound waves to electrical impulses.) Condenser mics use "phantom power" to create a charge differential between a suspended diaphragm and a fixed backplate. In either design, as the diaphragm is moved by sound pressure changes, the microphone translates that movement into electrical impulses.

Any decent music store or catalog will have a large selection of mics, but most of them will be mics designed for fairly specific sound reinforcement purposes or for recording of musical instruments. Some of these mics can also be useful for collecting sound in the field, or recording voice tracks in the studio, but conducting interviews and tracking narration have some special requirements.

The most basic distinctions we are concerned with are between Dynamic vs. Condenser, Directional vs. Omnidirectional, and Large Diaphragm vs. Small Diaphragm. None of these choices is universally superior, each has strong and weak points.

Dynamic Mics	Condenser Mics
Need no external power. Durable. Handle high volumes well.	Require Phantom Power Fragile. Louder output.
Common Examples: Shure SM-58, SM-57, SM-7 Electrovoice RE-50, RE-20, 635A Sennheiser 421	Common Examples: AKG 414, C-3000, C-1000 Neumann U-87, KM-series modular Sennheiser K6-series modular

Condenser mics are often a little more expensive, usually have a louder, more detailed output, but one should not overlook the benefits of dynamic mics, especially in the field. Dynamics are MUCH more forgiving of rough treatment, and do not require external power. Condenser mics break more easily if dropped, and require phantom power to operate, which must come from the recorder (draining batteries faster) a mixer, a preamp, or a separate power source. And even in the studio as an announce mic, Large Diaphragm dynamics such as the Electrovoice RE-20, Shure SM-7 and Sennheiser 421 produce very high-quality results. In the field, the overall durability and lack of phantom-power issues make dynamic mics very attractive.

There is often confusion between phantom power and preamplification. Although many preamps provide phantom power, they are separate power streams. All microphones require a pre-amp stage to raise levels approximately 60dB, but condensers, and some other types of mics, also require a low-level current to charge the diaphragm of the mic, setting up the electrical differential between the diaphragm and the backplate of the mic. Most modern mics want to see 48volt phantom power.

If your mixer or recorder will only turn phantom power on globally, that is, to all channels, and you are using a mix of mics, don't worry, the phantom power will not hurt your dynamic mics. (Although it can create some noise problems if applied to unbalanced line-level signals.) It is good practice to only turn on phantom power after all mics and cables are securely plugged in, and to turn off the phantom power at least a minute before unplugging the mics. This is absolutely crucial if one is using ribbon mics, and good form in any case.

Many condenser mics, especially those designed to be hand-held, can accept a battery to provide the phantom power. This eliminates the need for an external box if your recorder or mixer will not provide power, but also adds another battery that can drain at the least opportune moment.

Condenser mics almost always provide a louder output, reducing the often noisy preamplification stage. And condensers often give a brighter, more detailed sound.

Pick-up Lines

Either type of mic can have various pick-up patterns. Some mics can be switched to change patterns, or capsules can be screwed on and off, giving greater flexibility. Of course, these mics are usually more expensive than fixed-pattern mics, so if you're on a tight budget, you might want to choose a fixed-pattern mic that best suits your needs.

The most common directional pattern is called "cardioid" for its heart-shaped lobe of maximum sensitivity in front of the mic. Sounds to the sides and especially to the rear of the mic are largely rejected, or at least attenuated. Hypercardioids have an even smaller, more focused pattern, the most extreme example of which is the "shotgun" mic, which is meant to be used at greater distances. It's important to remember that even the most directional mics do not completely reject sound outside of the pick-up pattern. "Off axis" sounds are reduced in volume, but also often acquire a phasey or muffled character, sometimes making extraneous sounds seem rather odd. Sometimes, what's most effective for one purpose, such as reducing feedback on a noisy rock concert stage, is not as pleasing for another, such as an intimate commentary in a quiet room.

The next most common pick-up pattern is called "omnidirectional" for its ability to pick up sounds in all directions equally. Because of the mic's design, it has less of a focus on a particular direction, but also, off-axis sounds are picked up more accurately and naturally, lending a more realistic ambience. Some people mistakenly believe that omni mics will pick up close and distant sounds equally, making the background too loud compared to the primary source. But these mics must still obey the laws of physics, and focus on the subject can be achieved simply by getting the mic in close.

Both human perception of audio and the physical behavior of sound waves are measured according to the inverse square law, which is to say that in ideal conditions, sound intensity drops 6 dB (half the volume) every time the distance is doubled, and conversely, the volume doubles as the distance is halved. This gets more complicated based on the sound source and the actual acoustical properties of the space, but it remains a good rule of thumb. What this means for mic technique is that even an omnidirectional microphone can focus on the close sound, because the level of distant sounds decreases logarithmically with distance. And conversely, in most cases, in order to get good sound on tape, one must get the microphone close to the source because its sound pressure levels are dropping rapidly as you lengthen your distance.

Omnidirectional mics have the added benefit of being less susceptible to handling noise, and more tolerant of wind and plosives (popped "p" sounds and the like) and less "boominess" when close to the source, although, of course, not completely free from these problems.

Directional Mics	Omnidirectional Mics
Heightened focus on centered subject. More rejection of ambience. Needs precise mic placement, off-axis sources often sound bad. More susceptible to handling noise, wind and plosives.	Natural, "you are there" sound. Picks up more of surrounding ambience. More forgiving on mic placement, off-axis sounds are more natural. Less susceptible to handling noise, wind and plosives.
Common Examples: Shure SM-58, AKG C-1000, Sennheiser ME64 capsule, shotgun mics	Common Examples: Electrovoice RE-50, 635A, Sennheiser ME62 capsule, most Lavalieres

Does Size Really Matter?

Among the varieties of microphones covered above, there is yet another distinction based on the size of the diaphragm. Dynamic or Condenser, Cardioid, Omni, Figure-8 or other patterns, each of these can employ a large or small diaphragm. In general, handheld microphones will have small diaphragms, which are more durable, less susceptible to handling noise and air currents, and well...gee...they're smaller.

Large diaphragm mics are best suited for studio work in controlled environments, where they can be placed on a stand, preferably with a shock mount and a pop-filter. The larger, more flexible diaphragm gives a richer, more detailed sound with a higher sensitivity, and so is generally preferable for primary announcing duties. Even in the field, if circumstances allow conducting an interview while the subject is sitting in one place, it's worth considering bringing a large diaphragm mic, a stand and a pop filter, particularly if the interviewee is used to microphones (an experienced public speaker, a musician) because the overall sound quality will be better than with a smaller hand-held mic. But these large-diaphragm mics are very susceptible to extraneous noise and vibrations, and despite frequent claims by manufacturers of having integral pop-filters, they always need additional foam or mesh pop-reduction devices.

Small diaphragm mics can usually handle louder sources, and counter-intuitively, actually can have a larger frequency range, especially in higher frequencies, due primarily to the smaller diaphragm having less weight.

Be sure to read Jay Allison's excellent Basics of Field Recording column here in Transom Tools for tips on mic technique and interviewing strategies.

Yeah, but...

I know, I know, after all this blather, I still haven't told you what mic to get. The best answer is for you to try out a few and see what mic prefer for your style of reportage. The old reliable faves seem to be the omni EV RE-50 and the Beyer M-58, or the Sennheiser K-6 modular system with capsules of your choice.

Choosing a pattern is largely a question of taste and production style. Some producers prefer the open sound of an omni, others the closer, tighter sound of a directional mic. Some use short shotgun mics up close for interviews, giving a high degree of rejection of extraneous noise.

Avoid the temptation to use lavaliere microphones, at least for interview recording. Clipped to a lapel, or hanging around the neck, the lav mic is in a less-than-ideal position for good voice pick-up. Additionally, if the subject is moving around, clothes and cables will likely add unacceptable noise.

Here's a comparison of a small number of the more popular and/or affordable mics:

Electrovoice 635N/D (pdf file)	Dynamic, Omni, Small diaphragm	All-around workhorse reporter's mic. Cheap. Can hammer nails with it. (80hz-13khz)
Electrovoice RE-50 (pdf file)	Dynamic, Omni, Small diaphragm	Same microphone as the 635A, but with better pop filtering and isolation from handling noise. (80hz-13khz)
Beyer M-58 (pdf file)	Dynamic, Omni, Small diaphragm	Better frequency response than above mics (40hz-20khz), hotter output. Long handle.
AKG D230	Dynamic, Omni, Small diaphragm	Similar to RE-50, but with much wider frequency response (40hz-20khz)
Shure SM-58	Dynamic, Cardioid, Small diaphragm	The most popular all-purpose vocal mic in the world. Very rugged, good sound. Cheap. (about $100)
AKG C-1000	Condenser, Cardioid, Small diaphragm	Good frequency response (50hz-20khz,) uses standard 9 volt battery for power.
Sennheiser K6/ME66	Condenser, Short shotgun, Small diaphragm	Modular, can fit different capsule on K6 power supply. Very tight pattern, good for recording from medium distance. (50hz-20khz)
Sennheiser K6/ME64	Condenser, Cardioid, Small diaphragm	Modular, can fit different capsule on K6 power supply. (50hz-20khz)
Sennheiser K6/ME62	Condenser, Omni, Small diaphragm	Modular, can fit different capsule on K6 power supply. (20hz-20khz)
Neumann 180 series	Condenser, Small diaphragm	Omni, cardioid and hypercardioid mics. Very small. (20hz-20khz)
AKG C-414	Condenser, Variable Pattern, Large Diaphragm	Classic, versatile large-diaphragm condenser, suited for studio announce.
AKG C-3000	Condenser, Cardioid, Large Diaphragm	Affordable large-diaphragm condenser, with sound similar to AKG 414.
Neumann U87	Condenser, Variable Pattern, Large Diaphragm	THE big, warm announce mic. Large-diaphragm condenser with superb sound. Pricey.
Neumann TLM 103	Condenser, Cardioid only, Large Diaphragm	Affordable Large-diaphragm condenser with Neumann sound. (About $700)
Electrovoice RE-20 (pdf file)	Dynamic, Cardioid, Large Diaphragm	Perhaps the most common on-air announce mic. Warm, flat sound. Good pop-rejection. (45hz-18khz)
Sennheiser 421	Dynamic, Cardioid, Large Diaphragm	Versatile mic effective on everything from voice to drums. (30hz-17khz)
Rode NT1	Condenser, Cardioid, Large Diaphragm	Very inexpensive large-diaphragm condenser (about $200) Good sound quality, similar to Sennheiser 421, but louder. (20hz-20khz)
Oktava 319	Condenser, Cardioid, Large Diaphragm	Another very inexpensive large-diaphragm condenser mic (about $200 in some stores and catalogs) rounder, warmer sound than AKG or Rode.

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