While dynamic mics rule the stage, the full-range sound of a condenser microphone has made the condenser mic a top choice in the studio. Indeed, legendary condenser mics like the Neumann U 87 and the AKG C414 have been mainstays in recording studios for decades. Condenser microphones are ubiquitous in the studio, used for everything from vocals to acoustic instruments to drums to guitar cabinets. It’s safe to say that most recordings of the past several decades were created with at least one — if not several — condenser mics. When audio engineers demand the utmost in detail and clarity, a condenser microphone is most often their go-to solution.
Anatomy of a Condenser Microphone
Condenser microphones contain a thin, stretched conductive membrane positioned close to — and parallel to — a metal back plate. This is called the diaphragm. This layout essentially forms a capacitor, hence the condenser’s common alternative name, “capacitor microphone.” When sound waves encounter the diaphragm, they cause the membrane to vibrate. As the distance between the membrane and back plate varies, the variance results in capacitance changes, which, in turn, creates the output signal of the microphone.
Condenser mics employ an onboard amplification circuit to ensure a sufficient signal level. Most modern condensers employ solid-state amplification circuitry. That said, vintage-style, tube-based condenser microphones are coveted for their ear-grabbing harmonic characteristics.
Characteristics of a Condenser Mic
As we noted earlier, condenser microphones deliver a very detailed sound, making them a first choice for recording the full frequency range of vocals and acoustic instruments. These mics feature microns-thin diaphragms, which allow them to excel at capturing high frequencies better than other microphone designs. And their transient response is such that they can effectively track rapid-fire bursts of sound such as spiky hand percussion and plucked acoustic instruments.
Condenser mics are also extremely sensitive, enabling them to capture room ambience along with your intended source. This is part of what lends a studio-quality sheen to professional recordings. Unfortunately, the sensitivity of a condenser microphone can also be detrimental when used in an untreated space by highlighting the room’s subpar acoustic qualities. This can result in a recording with excellent detail but an unpleasant, box-like quality. Or, worse yet, your recording will be marred by barking dogs, a nearby television, or your neighbor’s lawn mower or even quiet, mostly undetectable sounds like rumble or air-conditioning fan noise. In an untreated space, a high-end dynamic microphone like the Shure SM7B or the Electro-Voice RE20 is generally a better way to go.
Condensers are also available with different-sized diaphragms. When most folks picture a condenser microphone, they usually envision a large-diaphragm condenser. These are the hefty side-address mics you’ll often see in front of a vocalist. Large-diaphragm models aren’t the only condenser mics in existence, however. Small-diaphragm condensers — a.k.a. pencil condensers — are almost as common. Small-diaphragm models, such as the Neumann KM 184 and Shure SM81, are frequently used for miking acoustic instruments. Beyond that, it’s extremely common to use a stereo pair of pencil condensers as drum overheads among other applications.
Polar Patterns and Condensers
Nearly all condenser microphones include a unidirectional cardioid polar pattern. That said, many condensers also boast omnidirectional, figure-8, and other polar patterns for added versatility.
A cardioid polar pattern is most sensitive to sound entering from the front. The sides offer moderate rejection, and the rear offers significant rejection. This makes cardioid mics ideal for recording vocals and other close-miked sources. With a cardioid polar pattern, you need to be wary of proximity effect, which enhances low frequencies when the mic is positioned close to a sound source.
An omnidirectional polar pattern is equally sensitive to sound from all directions. Omni-equipped microphones are great for capturing room ambience along with your sound source. Hence, they’re ideal for orchestral recordings. An omnidirectional polar pattern can also deliver natural-sounding vocal recordings since it doesn’t suffer from proximity-effect issues. That said, an omni polar pattern will accentuate bad acoustics in a profound way, so it’s a poor choice for recording in untreated spaces.
A figure-8 polar patten is bidirectional. It’s sensitive to sound coming from the front and from the rear but offers near-absolute rejection from the sides. A figure-8 polar pattern isn’t as widely used as cardioid or omni, but it’s capable of many advanced mic applications, such as mid-side and Blumlein stereo techniques. For more information on stereo miking techniques, check out this article.
Aside from the common cardioid, omnidirectional, and figure-8 polar patterns, there are also supercardioid and hypercardioid mics, which offer more directionality than a standard cardioid but with less rear rejection. Supercardioid and hypercardioid polar patterns are ideal for safeguarding against bleed from adjacent sound sources, such as a hi-hat bleeding into a snare-drum mic. Wide cardioid mics are also available, which are essentially less directional cardioid mics. A wide cardioid polar pattern is great for recording acoustic instruments and small vocal groups.
Powering a Condenser Microphone
As we noted earlier, condenser microphones employ an amplification circuit to boost the mic’s signal to a sufficient level. In the majority of circumstances, this circuit is powered by phantom power, which is provided by a console, a mic preamp, or a standalone phantom power unit. Phantom power, commonly designated as +48V or P48, is a way of providing voltage to the mic’s diaphragm and the mic’s internal amplification circuit through a balanced XLR cable. Unlike tube mics . . .
Tube condenser microphones are powered differently than their solid-state brethren. Tube mics are powered by a dedicated external power supply usually housed in a box the size of — and often the weight of — a brick. As inconvenient as these bulky power supplies may be, that’s the price we pay for the sublime, tube-fueled magic yielded by red-hot plates and wire inside a glass bottle.
There is also a type of condenser microphone known as an electret condenser. Electret condensers feature a permanently charged capsule and don’t require an external polarizing voltage. These mics will, however, still require power for the electronics, either from a battery or phantom power.
Conclusion
Whether you’re searching for a vintage-style tube condenser mic like the Warm Audio WA-251, a modern state-of-the-art mic like the Lauten Audio Atlantis FC-387, or a value-packed stereo pair of small-diaphragm condensers like the sE Electronics sE8, Sweetwater has you covered. Give your Sales Engineer a call at (800) 222-4700, and we’ll set you up with the perfect condenser microphone for your needs and budget.