Whether you have a closet full of mics or are contemplating your very first microphone purchase, selecting the proper mic for a recording application is crucial. Based on the e-mail I receive from EM readers, and on recurring discussions at audio newsgroups, it would also seem that deciding which mics to buy (and what to do with them once you have them) can be an agonizing process.
This article will help beginning recordists understand the three main classes of microphones-dynamic, ribbon, and condenser-and how they differ from one another, and explain why one type may be preferable over another for different recording applications. Before getting into specifics, though, let's identify some features that most microphones-whether for studio or stage-share. Perhaps the most important of these features is the diaphragm, a lightweight, delicate membrane that responds to changes in sound-pressure level. Protection for the diaphragm is provided by a wire-mesh or other type of grille, which typically also serves to identify the address, or active, surface of the mic.
The physical energy of the diaphragm's movement is transduced (that is, changed to electrical energy) by a variety of methods, each of which belongs to a distinct category of microphone electronics. Subsequently, the internal electronics provide an output signal via a male 3-pin XLR or multipin jack.
MICS YOU CAN EAT
The most common type of microphone is the dynamic. Most dynamic microphones employ a relatively massive, moving-coil diaphragm that is impervious to damage from rough handling or extreme sound pressure. The low cost and rugged construction of dynamic mics make them ideal for live sound, and certain models made by Shure, Sennheiser, Audix, Beyerdynamic, AKG, and Electro-Voice often do double duty in the recording studio.
With very few exceptions, modern dynamic mics are front address and designed for unidirectional pickup in a cardioid polar pattern. This means that sound arriving on-axis (that is, in front of the mic at the end of the cylindrical body) is emphasized, while sound arriving off-axis (that is, at the sides and rear of the mic) is suppressed or rejected.
FIG. 1: The cardioid pattern resembles the shape of an apple, with the microphone as the stem.
FIG. 1: The cardioid pattern resembles the shape of an apple, with the microphone as the stem.
The term cardioid derives from the heart-shaped pattern of the microphone's "hot zone," or on-axis area. However, I find it easier to think of the pattern as being in the shape of an apple, with the microphone as the stem (see Fig. 1). This pattern has obvious benefits for live sound, where monitor speakers may be placed in front of a performer-and therefore are pointed at the rear of the microphone. But dynamic mics are also an asset in the studio, where their focused pattern and limited sensitivity to distant sounds is useful for "tuning out" unwanted sound sources.
The dynamic mic is always the best candidate for controlling leakage (when excess room sound or the sound of other instruments "leaks into" the mic) and, likewise, for maintaining the maximum separation of sounds when close-miking. This makes it a natural choice for miking a drum kit, where, for instance, the snare-drum mic may be within two to three inches of both a tom-tom and the hi-hat cymbals. Models such as the Shure SM57 and Sennheiser MD 421 are preferred by many engineers for snare and toms, respectively, as well as for some hand drums. Dynamic mics are generally not used for high-frequency sources such as cymbals and metallic percussion and are not optimal for distant miking of room sound or a group of instruments.
Some dynamic mics are specially designed for recording bass drum, and they feature an extended low- frequency response as well as a high-end emphasis to bring out the attack of the bass-drum pedal. These mics can also be put to good use on acoustic bass, tuba, and speaker cabinets for electric bass and organ.
Though leakage is rarely a problem when miking guitar amps, dynamics are also widely favored for this application. Because most dynamic microphones have a midrange frequency response that is optimized for vocals, they will enhance the equivalent range of amplified guitar tones as well as that of brass-band instruments. And, in contrast to other types of microphones, the dynamic is unfazed by high sound-pressure levels and can further aid the engineer by filtering out boomy lows and grating highs at the extremes of the frequency spectrum.
Vocalists accustomed to using handheld dynamic mics on stage may feel more at home using them in the studio and, in some cases, will prefer the sound of a dynamic over a more expensive condenser microphone. There is no reason not to try a blue-collar dynamic as a main vocal mic; George Benson's "This Masquerade" is a good example of a hit song in which the vocal was recorded with a dynamic microphone. For singers who like to "eat the mic" but don't want to produce a disproportionate amount of bass response (due to the proximity effect), some deluxe models provide low-cut filters. This feature enables the user to trim the low-frequency output of the mic via single or multiple switch positions, and typically it's the only "extra" found on dynamic mics.
MICS YOU SHOULD BABY
The ribbon, or velocity, microphone is an early form of dynamic mic that was ubiquitous in broadcasting, film sound, and music recording from the 1930s through the 1960s. Vintage RCA ribbons can still be found in studios today, and three companies-Coles, Royer, and AEA-are continuing to make microphones based on classic figure-8 (also known as bidirectional) designs.
FIG. 2: Sounds from the side of a classic ribbon mic are rejected because the suspended ribbon can’t move from side to side. The pickup pattern, if visualized from above the mic, resembles the numeral 8.
FIG. 2: Sounds from the side of a classic ribbon mic are rejected because the suspended ribbon can’t move from side to side. The pickup pattern, if visualized from above the mic, resembles the numeral 8.
Because its "diaphragm" is a thin rectangle of metal foil suspended vertically, the traditional side-address ribbon mic is extremely responsive to sound arriving at either the front or the back of the grille, while sounds from the side of the mic are rejected because the suspended ribbon can't move from side to side. Therefore, the pickup pattern, if visualized from above the mic, resembles the numeral 8 (see Fig. 2).
Classic ribbons are known for having a flat frequency response with a smooth, softened high end that can be magical on brass instruments, bowed strings, and some saxophones and reed instruments. Ribbon mics can also be very effective for medium-distance miking (4 inches or more from the grille cloth) of electric- guitar cabinets as well as for distant room miking of single instruments or ensembles. And for re-creating the warm, roomy qualities of a vintage jazz or pop recording, the ribbon mic is an obvious choice, as evidenced by its popularity with the swing-revival set. As an alternative to the bulky and costly ribbon designs of yesteryear, Beyerdynamic makes a number of hybrid, short-ribbon mics with both figure-8 and unidirectional pickup patterns.
There are some important caveats to consider when choosing ribbon mics for a job. Foremost is the fragility of the ribbon, which must be protected from plosives and other strong blasts of air. Extreme sound pressure, such as that from a bass drum, a loud amplifier, a vocalist's popped "P"-or even from slamming the lid on the mic case-can stretch or destroy a ribbon. Phantom power can also ruin a ribbon and therefore should not be used. In addition, ribbon mics do not have a high output level, so it is important to pair them with a quiet microphone preamplifier with lots of gain.
Dùng mic phải hiểu về mic ...
Dạng Threaded
