Microphone Types

All information below provided by Paul White at  http://www.soundonsound.com/sos/apr98/articles/mic_types.html

MIC TYPES & CHARACTERISTICS

The type of mic you choose for a given task can have a profound effect on the quality of the resulting recording. 

THE DYNAMIC MIC

The live music market accounts for the majority of low-cost dynamic microphone sales (that's not counting the really cheap, nasty models inflicted on the domestic audio market), but a significant number of these mics also end up in home studios. By examining how this type of microphone differs from the 'perfect ear', it's easier to get a handle on what they might reasonably be expected to cope with.

"Dynamic mics are useful when the sound source is close and reasonably loud."

A typical budget dynamic mic has an upper frequency-response limit of around 16kHz, as opposed to the 20kHz or so of a good capacitor mic. The human hearing range is always quoted as extending up to 20kHz, even though few can actually match this. Subjectively, the result of this curtailed upper response for dynamic mics is that most of them don't do justice to very high-frequency sounds such as cymbals, bells, or the upper harmonics of the acoustic guitar or piano. They'll make a fair stab at the job for demo purposes, but if you compare the result to that achieved with a capacitor mic, you'll notice that a lot of the 'air' and transparency around the top end is missing.

CAPACITOR MICS

Capacitor microphones are the mainstay of professional recording and are characterised by high sensitivity and a good high-frequency response. Though a capacitor mic can tackle any job that a dynamic model can, dynamic models still tend to be used for bass drum and tom recording because of their physical strength (drummers are notoriously bad shots!), and because of their good mid-range punch. However, some engineers use capacitor mics for drum-kit recording where a more natural sound is required -- in jazz recording, for example.

Studio vocals are generally recorded with capacitor mics, though some rock singers like to use their dynamic models to give them a more punchy, middly sound. Mick Jagger and Phil Collins are reputed to prefer recording via dynamic models, so even if you do have access to capacitor mics, try recording your vocals via your dynamic mics and compare the results. You might be surprised at which you prefer.

"Capacitor microphones are the mainstay of professional recording."

BACK-ELECTRET MICS

It's usual to see back-electret mics as the poor relations of the true capacitor microphone, but this is a largely unfair perception. The capsule construction of the back-electret mic is essentially the same as for the capacitor model, except that the charge for the capsule comes from a permanently charged electret material fixed to the capsule back-plate. Indeed, some of the best studio mics, such as those made by B&K, use back-electret capsules. However, the nature of a back-electret capsule means that it is generally considered impractical to build a multi-pattern model working on that principle. For that reason, all the back-electret mics I know of have a fixed polar pattern, or one that can be modified by acoustic means only to provide differing widths of cardioid pattern.

All Information  below is provided by: http://www.btinternet.com/~paformusic/mics.htm

Omni-directional or Uni-directional

• Omni-directional mics pick up sound with equal sensitivity from all directions. This is not normally useful for PA work, because in PA work each mic is targetted at a single sound source (so that the amplification given to that sound can be controlled separately from others, and so that pick-up of unwanted sounds can be minimised). Their application is generally limited to recording work (particularly of ambient sounds) and to sound-level measurement.
• Uni-directional mics pick up sound with greater sensitivity from the front than from other directions. There are several variations on this theme. Each of the following types is illustrated with a polar response diagram, in which increased sensitivity in a particular direction is indicated by the line on the diagram being closer to the outer circle. Imagine the microphone diaphragm being located at the centre of the circle, with the most sensitive end (or side) of the microphone facing towards the top of the circle. So, the upper-most point of the line on each diagram indicates the sensitivity at the front of the microphone, or at '0 degrees' − i.e. the on-axis response, and the lower-most point indicates the sensitivity at the back, or at '180 degrees'. (The diagrams below are simplified to illustrate typical mid-frequency responses; in practice the polar responses vary with frequency, so check the manufacturer's specifications.)

  Sub-cardioid mics have a very gradually reducing sensitivity from the front to the back, maintaining some sensitivity at the back.
  Cardioid mics have a gradually reducing sensitivity from the front to the back, with very little sensitivity at the back.
  Super-cardioid mics reduce their sensitivity from the front to the sides at a faster rate than cardioid types, reaching a minimum sensitivity at an angle of around 120-140°, measured from the front. The sensitivity then increases again towards the back, but the sensitivity at the back is still very much less than at the front.
  Hyper-cardioid mics provide even less sensitivity at the sides than do super-cardioid types, at the expense of a little more sensitivity at the back. Therefore, a monitorspeaker should never be placed directly behind this type of mic. Their minimum sensitivity is at an angle of around 100-120°, measured from the front.
  'Rifle' or 'shotgun' mics are the most directional type, so-called because of their long rifle-like barrels. They are generally used only for long-distance miking (more than 2 metres from the source), e.g. for theatrical work, and should be located such that the back of the mic is not exposed to unwanted sounds.

• Bi-directional types

  Although not featured in the title of this sub-section (as they are rarely used in live PA work), bi-directional mics get a mention here for completeness. They pick up sound with equal sensitivity from two opposite directions, shown in the diagram as the front and back; in practice however, as these are usuallyside-addressed types, the sensitive directions are most commonly on two of its sides.