Microphones - Let’s be honest with ourselves for a minute. It’s a whole lot more fun to spend money on gizmos with lots of lights, knobs and buttons than it is to buy boring old microphones. Mics just sit there on their stands, dutifully feeding signal to the true stars of the sound system—the electronics. Right?

Wrong. The microphone handles the most-crucial conversion of energy in the whole sound system, where sound energy becomes an electrical signal. If you don’t have the right microphone positioned in the right place, no amount of after-the-fact processing will give you optimum sound.

In this article, we’re going to give you the straight scoop on how to choose and use microphones. We’ll cover the differences between microphone types, microphone pickup patterns, specs that matter and more.

Family Affair

We can divide the microphone world into two major families based on how they convert changes in air pressure (also called "sound") into electricity. Dynamic mics are the simplest and most rugged of the two. A dynamic mic works like a loudspeaker in reverse, creating an electrical signal as a tiny coil of wire moves through a magnetic field. Dynamic mics generate a signal without any internal electronics, batteries or power supplies. Hence you can patch one into the mic input on most any sort of mixer or recorder and be guaranteed sound.

Condenser mics are a little more complex. They use a different method of converting sound to electricity, one that is more accurate but generates a much smaller signal. The resulting signal is too weak, in fact, to survive outside the microphone. So condenser mics have electronics built right into them to amplify the signal. These electronics require power, which often comes from a built-in battery. Higher-end condenser mics usually get their power from the mixer through the mic cable itself--this is called "phantom power." Condenser mics have grown so popular that even inexpensive mixers offer phantom power.

Because they’re so simple, dynamic mics are usually more rugged than condenser mics. They don’t require phantom power, and they have no batteries that can run out at inopportune times. Dynamic mics also tend to be a little more affordable than condenser mics.

The main benefit of condenser mics is their clear, natural sound. Condenser mics usually offer a more extended and detailed high-frequency response than dynamic mics, which translates to better clarity and crispness. Many condenser mics will do double-duty, delivering great sound both on-stage and in the studio. Manufacturers are making condenser mics more sturdy as time goes by as well.

Dynamic mics are used frequently for vocals, and most dynamics have a built-in pop filter to reduce loud thumps from consonants like "p" and "b." Though there are plenty of condenser mics designed for vocal applications, many condensers lack a pop filter and are better-suited for instrument pickup.

The extended high-frequency response of the condenser also makes it a natural choice for cymbals, percussion and other "bright" sounds. Once you get to a certain price point, differences between mic types grow less pronounced. There are dozens of dynamic and condenser mics in the $150-$400 range that are excellent performers regardless of what type of instrument (or voice) you put them in front of.

It’s a Pattern

Along with how it converts sound to electricity, a mic’s pickup pattern has a large impact on its sound and suitability for certain applications. Without engineers to implement some clever tricks of physics, every basic microphone would be omnidirectional. In other words, the mic would pick up sounds at the same volume regardless of their origin. This non-discrimination policy may seem like a good one at first glance, but it can create problems in the real world.

Omnidirectional: An omnidirectional mic faithfully picks up every sound in its vicinity, whether you want it to or not. This means an omnidirectional mic will pick up loud and clear a guitar amp sitting just a few feet away from an acoustic piano, or a blaring floor monitor at a singer’s feet. The result would probably be an uncontrollable mix in the first example and runaway feedback in the second. Mics that are sensitive to sounds coming from just one direction are more practical. We call these directional mics, and they’re the most popular type of microphone used for stage and studio alike.



Cardioid: The most common directional pattern is called "cardioid" because of its heart-shaped pickup pattern. The mic’s sensitivity gets progressively lower as a sound source moves around to the side of the mic. When the sound comes from directly behind, the cardioid mic picks up very little. This allows you to point the mic at sounds you want to pick up and away from those you don’t.


Supercardioid: Supercardioid and hypercardioid mics are progressively tighter variations on the cardioid pattern. They narrow the angle of pickup in front of the mic, giving them better rejection of sounds coming from the sides. There is a trade-off, however—these mics are more sensitive to sounds coming from directly behind them. If maximum rearward rejection is your goal, you may be better off with the looser cardioid pattern.

It’s important to understand that directional mics (even those with a hypercardioid pattern) aren’t all that directional. A cardioid mic, for example, may pick up sounds with little change in volume across a 150-degree arc in front of it. That means that sound sources perpendicular to the mic will be nearly as strong as those directly in front.

Supercardioid and hypercardioid mics narrow this angle to roughly 130 and 110 degrees respectively. Just remember that no microphone is directional enough to completely "home in" on a given sound and ignore all competing noises. Sound just doesn’t work that way.

The Spec Game
How much can you learn from a microphone’s spec sheet? In reality, not much. Before you scrap that stack of product brochures, however, here are a few specs that may offer some help in your buying decision.

Frequency Response
This numerical range tells you where a microphone’s response begins to taper off both in the very low and very high registers. Expressed in Hertz or Hz (both meaning cycles per second), lower numbers are better on the first spec and higher numbers on the latter. For most instruments and voices, a mic’s high-frequency response is probably the more meaningful spec. In theory, a mic with a higher frequency response (17,000 Hz, for example) should have a more open, detailed sound than one whose high frequencies begin tapering off at 12,000 Hz. Because a simple number doesn’t give you the full picture, however, you’re better off looking at a frequency response curve.

Frequency Response Curve
This wavy line actually shows you the mic’s sensitivity at various frequencies, and will give you a glimpse into the sonic character of the mic. A chart that slopes upward and has bumps above about 3,000 Hz or 4,000 Hz may have a bright, crisp character. Mics with very flat frequency response lines tend to sound more natural or even have a "dark" character.

Sensitivity
This spec is meant to tell you how much signal a mic generates for a given amount of sound. A more-sensitive mic is generally better, as it puts out a stronger signal less prone to noise. Unfortunately, there are several standards manufacturers use for measuring sensitivity, and converting between them almost requires an engineering degree. If you can find two mics measured with same standard, you’re in luck.

Maximum SPL
This spec tells you the loudest sound the mic can handle without distorting, and higher numbers are better. Most mics today handle extremely loud sounds without flinching, so this spec isn’t quite as important as it used to be. Still, mics with maximum SPL specs of less than about 120 dB may distort when placed in front of a trumpet or stuffed inside a bass drum.

Noise
Remember those active electronics packed inside every condenser mic? Turns out they create some noise as they amplify the tiny condenser signal. Like sensitivity, there are a few different ways to measure a mic’s noise output. If the spec lists "Noise", lower numbers are better. If it lists "Signal-to-Noise Ratio" or "S/N," higher numbers are better. Only if a mic shows a noise figure approaching about 30 dB (or a signal-to-noise ratio of less than about 65 dB) will noise be a real problem, and probably only when miking softer sounds. Dynamic mics generate no appreciable noise of their own, so a noise spec isn’t needed.

Listen Up
You can’t know how a car handles until you drive it, and you won’t be sure a coat fits until you try it on. Likewise, no amount of spec-studying or brochure reading will really tell you how a given microphone sounds. You need to listen to it, ideally in your own environment, to be sure it’s a good choice. If you can rent a few mics and compare them, you’ll find it even easier to find the right microphone for your purposes.

Remember: when it comes to choosing and using microphones, you have to trust your ears.