What is a condenser microphone?

Anybody looking to add a microphone to the stable has likely encountered the term condenser microphone. Let’s check out what a condenser mic is and which recording applications they work best for.

Editor’s note: this is the first version of the article. Updates will follow as the market changes.

What is a condenser microphone used for?

Condenser microphones are known for capturing sound cleanly and clearly over a broad frequency spectrum. Given those attractive features, condenser mics suit vocalists very well. These versatile microphones tend to have low self-noise but require phantom power from a microphone preamplifier to work. Most audio interfaces have integrated preamps these days, so it’s unlikely you’ll need an outboard one to power your mic.

You can use a condenser microphone for almost all recording applications. For example, I use two matched small-diaphragm condenser microphones as overhead microphones for drums. While drums are loud, the fast transients and trebly sound of cymbal hits suit the extended high-frequency response that many condenser mics offer.

On the flip side, you could stick a condenser in front of an acoustic guitar to record all the details, from the pick attack to the sounds of fingers sliding along the strings.

What disadvantages do condenser microphones have?

Of course, if condenser microphones were perfect for every task, you wouldn’t need other kinds of mic. Once you consider the strengths of condenser microphones in one context, you’ll realize those might be weaknesses in different contexts. For instance, most condenser microphones, except for lavalier-style microphones, do not fare well in live performances when you typically reach for a dynamic mic instead.

You want to avoid taking your studio condenser onstage. One of the reasons the Shure SM58 (a dynamic microphone for $99 at Amazon) is so ubiquitous is due to its excellent off-axis noise rejection, requiring the sound source to get quite close for good capture. Plus, it has low handling noise and a very durable design — characteristics not shared by most condenser mics.

Grey areas in choosing a mic

Choosing the right mic for the job is part science, but it’s also an artistic decision. Overall, you can use a condenser or a dynamic mic in plenty of situations. Use your judgment, and play to the strengths of the mics you own.

If you’re a podcaster you can grab a condenser mic, but if you’re in a crowded or noisy space, you might nab a broadcast-style dynamic microphone like an Electro-Voice RE20 ($449 at Amazon) or Shure SM7db ($499 at Amazon). While most singers like condenser mics in the studio, sometimes one of those broadcast mics matches the singer’s voice better. Use your ears to decide.

How do condenser microphones work?

Virtually all microphones utilize a diaphragm, an extremely thin, conductive material. Located under the protective grill of the mic, it’s responsible for responding to sound waves. On a condenser mic, the pressure from sound waves physically moves the diaphragm, used in concert with an electrically charged metal plate. Using induction (also known as electro-magnetism), the moving diaphragm sends current to the charged metal plate.

From there, if it’s an electret condenser, an impedance converter circuit follows the charged metal plate. Essentially, this creates an audio signal for your preamp. There are variations on this, but that’s the basic design.

What’s the difference between an electret and a true condenser microphone?

These days, most condenser mics are electret condenser mics, also known as fixed-bias mics. Modern mics require phantom power (standard 48v from the preamp) to charge the metal plate in the condenser mic adequately. Electret condensers work with balanced circuits via the XLR cable, with pins two and three each carrying both the audio signal and 48v DC relative to pin one, which is tied to ground.

Much less common are true condenser microphones, which require an additional device to bias the charged metal backplate externally. Neither is better or worse unless you count convenience; in this case, not needing a second external device is less cumbersome than just plugging in an XLR cable and using phantom power with an electret condenser.

Do condenser microphones have different polarity patterns?

You can find virtually every available polarity pattern in a condenser microphone. Your options range from the common cardioid (named for its vaguely heart-shaped pattern) to figure-eight, omnidirectional, hyper-cardioid, and more. Many condenser mics come with a switch to choose a pattern — vastly extending the flexibility of any mic. Some condenser microphones are modular, so you can swap out the microphone capsule for another to get more applications out of a single mic.

If you’ve got a whole acoustic band playing in a room and only one mic to record the group, grab an omnidirectional (or well-placed figure-eight) condenser mic. It’ll catch every instrument. It won’t usually be perfect, but it’ll sound much better than trying the same thing with a cardioid like a Shure SM58.

Exceptions to the rules with condenser mics

So, while it’s generally true that a condenser mic is best suited to a recording studio or controlled space like a YouTuber’s room, there are purpose-built exceptions. Here’s a quick rundown beginning with shotgun microphones.

Shotgun microphones are specialized for film and video.

Shotgun mics are so named because they are typically long and ruggedly built. Generally, shotgun mics are mounted to a boom pole held by someone standing out of frame while filming to record speech. Because any handling tends to introduce unwanted noise, these usually incorporate shock mounts to offset that problem. They tend to have hypercardioid polar patterns. Still, most of the time, if you’re filming outside of a closed set, you’ll use a Lavalier microphone or a handheld dynamic mic for a newscaster. In a pinch, you can use a shotgun for unorthodox applications, but due to their dimensions, they are not ideal for podcasting, for example.

Lavalier microphones have many uses.

A Lavalier mic is a tiny condenser microphone with a lapel clip. Usually, they’re wired to a transmitter pack that uses radio frequencies to transmit the captured audio to another device to record. These are frequently found in settings like interviews, lectures, and sometimes on acoustic instruments like violins. They also have the advantage of a discreet size, which can feel less intimidating, particularly for “mic-shy” people.

Field recorders frequently have built-in mics.

Field recorders, or the more straightforward voice recorder, usually use condenser microphones. The ever-popular Zoom series of field recorders, such as the Zoom H5 ($249 at Amazon), includes two condenser mics pointed at 45-degree angles away from each other. The point is to record a wide swath of sound sources, whether out in nature or an indoor interview.

This works great if your goal is to capture everything. Unlike conventional studio condenser mics, which aren’t exactly made for applications outside treated rooms, the ones found in field recorders have been constructed robustly. This mitigates the effects of accidental knocks and diffuses some handling noise.

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