Among the multitude of audio technology inventions, microphones remain an essential element of any recording studio, live performance, or broadcasting environment—in fact, it feels impossible to imagine the modern world without them. While microphones were once crude telecommunications devices, they've evolved over the last century into highly refined tools for capturing highly detailed sound...from vocals to field recordings, guitar cabs, and symphony orchestras.

Of course, the sheer variety of these highly specialized devices means that choosing a microphone for your personal recording setup can be a challenging task. Because different types of microphones tend to be better suited for different recording or live sound reinforcement situations, learning the meaning of various microphone specifications is critical to making an informed decision that will capture your sound clearly and keep the process of performing or recording as smooth and enjoyable as possible.

While there are quite a few things that need to be considered when choosing the right mic for the job, in this article we are mainly going to focus on one of the most fundamental concepts of microphone design—microphone operating principles. We discuss other specifications (like what microphone polar patterns mean) in other articles, but for now, let's focus on the basics: what is the difference between a dynamic microphone and a condenser microphone? Which is better for vocals, guitar, or synths? When should you consider using a ribbon microphone? Let's set out to find some answers.

What Makes Microphones Different from One Another?

So first things first—what are microphones, and how do they work? What kinds of microphone designs are out there?

A microphone is a transducer—a device that converts sound waves (fluctuations in air pressure) into an electrical signal, which can then be further amplified or recorded. Essentially, most microphone designs (except piezoelectric mics) are centered around a diaphragm—a thin plate made out of different materials hidden inside a microphone's capsule. The diaphragm is so thin and delicate that it can vibrate in sympathy with minute fluctuations in air pressure.

The biggest difference between the distinct types of microphones comes down to The nature of the material used for the diaphragm, as well as how precisely the sound waves are then converted into an electrical signal. Although the topic of microphone operation principles is large enough to dedicate a full article to each, we're going to give you a high-level overview of the three main mic categories that are by far the most prevalent in today's world: dynamic, condenser, and ribbon microphones.

What is a Dynamic Microphone?

Dynamic microphones (aka moving-coil microphone) are based on the principle of electromagnetic induction, where the microphone's diaphragm is attached to a small moveable coil of wire, and placed inside a magnetic field of a permanent magnet. When a sound hits the diaphragm, it forces it to vibrate inside the magnetic field, effectively causing an alternating current to flow in a circuit following a pattern similar to the incoming sound waves. This creates a clean, clear microphone response without being too sensitive, making it great for a wide variety of tasks.

So, dynamic microphones can handle a large number of tasks: and if your sole goal is to record your guitar cabinet, or to do live vocal performance, a dynamic mic of some variety is likely to serve you best. But while dynamic mics are great at capturing loud sound sources and isolated sounds in noisy environments, they don't always offer the level of sensitivity and clarity that is required for more delicate recording scenarios. That's where condenser microphones come in.

What is a Condenser Microphone?

In condenser microphones, the diaphragm is made out of a thin metal plate which sits in front of another plate known as the backplate. Together, they form what in the world of electronics is known as a capacitor (in fact "condenser" is an older term for capacitors)—a device that can store small amounts of electrical energy. Sound causes the diaphragm to move, and the change in distance between the two plates effectively changes the electrical signal that passes through the circuit, once again mimicking the pattern of the incoming sound waves.

Unlike dynamic microphones, condenser mics are active, meaning that they require external power to function (aka phantom power), which is most often supplied through the same cable that the audio signal passes through, but in other cases can also be provided by an internal battery, a power adapter, or a USB connection. Phantom power is usually provided to a microphone from an audio interface, a mixer, or a mic preamp at the press of a button (often labeled "Phantom", "+48V", or similar). By nature of this design, condensers are excellent at picking up quieter sounds and subtle nuances, as well as delivering a better representation of the high-frequency content than is possible with a dynamic microphone. Also, overall they tend to deliver a much more natural reproduction of the source. However, this also means that condenser mics are much more sensitive to louder sounds, and are prone to distorting if the incoming signal exceeds the maximum sound pressure level (SPL) the mic is designed to handle. So while dynamic mics are usually better for picking up loud sounds, condenser mics often offer considerably greater sensitivity and high-end clarity for sounds that need it.

Large-Diaphragm Condenser Mics

Let's distinguish between two sub-types of condenser mics: large-diaphragm, and small-diaphragm condenser mics. Naturally, the former ones have a physically large grill, and they tend to have lower self-noise. Large-diaphragm condensers like the legendary Neumann's U 87 and U 47 are often a preferred choice for miking vocals, acoustic guitar, and drums as they add richness and scale to the sound. This is especially true in the world of studio recording, where capturing sound with the utmost precision and detail is critical.

Small-Diaphragm Condenser Mics

Small-diaphragm condenser mics such as the classic AKG C451 EB (now C451 B) are very compact, and they are great at picking up sounds exactly as they are, without any added coloration, as well as bringing out the subtleties. Because of these qualities, these kinds of microphones are often chosen as drum overheads, as well as for recording acoustic instruments, and entire orchestras.

What is a Ribbon Microphone?

We've discussed the various strengths and weaknesses of dynamic and condenser microphones: typically, you'd use a dynamic mic with particularly loud sound sources, or sounds that require strong isolation from ambient sounds or other nearby instruments. Condenser mics, conversely, are better for capturing minute nuances, making them a great choice for lead vocals, strings, or any instrument that benefits from a high degree of nuance. Sometimes, though, replicating sound completely cleanly and clearly isn't precisely what you want: sometimes, you want the microphone to add some subtle color and warmth of its own. Oftentimes, that's where ribbon mics come in.

Ribbon microphones are similar in their operational principle to the dynamic microphones, as both rely on electromagnetic induction, however here instead of the induction coil, a thin piece of metal ribbon is suspended in the magnetic field. Ribbon microphones are often characterized as possessing a pleasantly warm and smooth response, and for this reason, they are well-loved by many recording engineers, and artists. For any instruments where you want to take off the natural acoustic edge, or for anything you want to provide some unnatural, vintage-style warmth, a ribbon mic can be an excellent choice.

Microphone Operating Principles Encapsulated

So to recap—when should you use a dynamic mic versus a ribbon mic? When should you consider using a ribbon microphone? Well, typically, dynamic mics are best-suited for particularly loud sounds, or sounds that require isolation in noisy environments. That's why they're commonly used as live vocal microphones, guitar cabinet mics, and mics for the individual drums of a drum kit. Condenser mics are considerably more sensitive—so they're often less useful in noisy environments, but can help capture considerably greater nuance and detail when in a controlled environment. Ribbon mics intentionally sacrifice some of the nuance and realism of the other types in order to impart a pleasant warmth and silkiness, rounding out harsh edges and adding fullness to the original source sound...commonly useful for brass sections, edgy guitar cabs, and vintage-style vocals.

Hopefully these general guidelines will prove useful as you plot out which microphone to buy next (or first!). In a short article, we can only say so much about each specific type of microphone—but keep in mind that in actuality, the rules we've outlined aren't truly rules at all! In the real world, recording engineers typically have a broad selection of different types of microphones available. Moreover, they don't necessarily have a single "go-to" microphone for specific tasks—the best recording engineers instead listen to the sound at hand and choose from their arsenal of familiar tools whatever microphone or combination of microphones seems best for the job. Sometimes, that will mean using a condenser on a guitar cab, a dynamic mic on an acoustic guitar, or a ribbon mic on drums: as with any corner of musical creativity, it's about keeping your ears open and choosing what will help get you to the next step of the creative process as cleanly as possible.

That said, there's much more to come—in future articles, we'll discuss further concepts of microphone design, discussing polar patterns, specific miking techniques and more. Keep your eyes open, and until then, happy recording!