What is a Condenser Microphone and How Does it Work?

Condenser microphones are the more sensitive kind of microphones that are used for recording more detailed and sophisticated sounds. Dynamic mics are loved for their rugged design and construction, and they are the perfect tools for live concerts.

But condenser mics offer more precision in terms of details and clarity. You might remember from physics class that two metal plates nearby can create a high capacitance. This mic uses the same technology.

It uses two thin layers of metal plates close to each-other.  The diaphragm is electrically conductive on the surface. The most commonly used material for this purpose is gold-sputtered mylar, but earlier models of condenser microphones used extremely thin metal foils as well. 

For their use of this dual metal-plate technology, condenser mics are known as “Capacitors” in the UK.

How Do They Work?

Basically, a condenser microphone is a highly specialized capacitor. Meaning, it’s basically a passive electrical component that is designed in such a way that is capable of storing energy in an electric field temporarily. The two metal plates used in a capacitor in close proximity with each other.

They have the ability to store an electric charge depending on how close they are to each other. Usually, in a condenser microphone, one of the two metal plates is made of very thin material and it acts as a diaphragm.

What Is a Condenser Microphone

When sound waves hit the diaphragm, it vibrates and changes the distance between the two plates and thus changes the capacitance.  This fluctuation in capacitance then creates an electrical representation of the acoustic energy from the source of the input of the sound or the sound source.

Usually, the impedance of a DC-polarized capsule is very high. To break it down, impedance is the ratio of the complex representation of the sinusoidal voltage between the two-terminal circuit elements of a circuit or capacitor. Condenser mics require external power to charge their internal electronics.

To transform this very high impedance of a DC-polarized capsule's output to a usable level, an active circuitry is required. + 48V phantom power is the most commonly used impedance level for supplying current to this circuitry.

A few other methods such as using a dedicated power supply and batteries are also used for supplying phantom power to condenser mics.

Why Do We Use Them in the First Place?

Since its mass is extremely low (thanks to the lightweight thin metal plates used as the capacitor), the diaphragm of a condenser mic can follow sound waves much more accurately compared to dynamic mics that have a heavy moving coil attached to them.

This means they have a better, wider frequency response, and the best transient response (transients are fast bursts of energy, such as the attack of a drum or the “pick” of an acoustic guitar) out there.

Above all, condenser microphones offer a much higher sensitivity to even the lowest of sound waves, all while keeping the noise much lower than a dynamic mic.  For this reason alone, condenser microphones are the default tool for all kinds of studio recordings, be it vocal or instrumental.

Types of Condenser Microphones You’ll Find

There are a handful of variants of condenser microphones, based on diaphragm size, polar patterns, address orientation, connectivity, etc. Here I’ll try to briefly describe them.

Polar Patterns

A polar pattern is a 3D space around a mic’s capsule where the capsule is the most sensitive to sound signals.  The most commonly used polar pattern in most condenser microphones is the “Cardioid” pickup pattern.

The pattern gets its name from the Greek word “Cardio” meaning heart, due to its heart shape. The cardioid polar pattern has two other variants, Supercardioid, and Hypercardioid.

The Cardioid pickup pattern tends to be more sensitive towards sound waves coming from one side or the end of the microphone. While on the other hand, hyper-cardioid mics are considered more directional as they are less sensitive at the sides of the pickup pattern.

Super cardioid is totally different than these two and they are less directional than either of the two. Rather they offer the advantage of having a slightly smaller rear tube.

The omnidirectional polar pattern is, as the name suggests, equally sensitive to audio signals coming from all sides of the capsule. Although it is scientifically impossible for a mic to be 100% omnidirectional, that does not affect its performance as much that it’d be noticeable.

Then there is the bidirectional pickup pattern that forms a ‘figure-8’ graph and can pick up sound signals from both the front and the back.

Diaphragm Size

A condenser microphone’s diaphragm is what makes its sound quality so superior and sophisticated.

The low mass of the diaphragm allows the condenser microphone to vibrate in response to the sound waves that hit it, and as a result, you get a more accurate sound than that of a heavy moving coil inside a dynamic mic.

Here the size of the diaphragm is crucial because it affects how the mic responds to the sound waves. If the diameter of the diaphragm of a mic is an inch or above, it is considered a large-diaphragm mic.

If the diameter is ¾ of an inch or less, it is known as a small-diameter mic. There is another popular variant of the large-diaphragm capsule called the ‘electret’ diaphragm capsule.

The word “Electret” is formed by combining the words ‘Electrostatic’ and ‘Magnet’. It is formed by drawing an analogy to the formation of a magnet by aligning magnetic domains in a piece of iron.

Orientation

The orientation of the focal point or the area of the diaphragm where the mic is the most responsive to the sound source determines whether it is side-addressed or front-addressed. Most small-diaphragm mics are shaped like a pencil and are designed to pick up sound from the end instead of the sides.

Microphones with Large Diaphragms on the other hand, usually are side-addressed. Regardless of the orientation, both the mics are equally useful, but knowing about the orientation helps you to visualize its polar pattern more clearly so that you can target the mic more accurately to the sound source.

Dynamic and Condenser: What Makes Them So Different?

We all have some basic idea that condenser microphones are slightly different from dynamic microphones, mostly due to their applications. But did you know that the two types of the mics are totally different from each other when it comes to their material, design, and technology?  Let me elaborate.

Dynamic Mics

Dynamic Microphone

Dynamic mics are built with a single magnet on the inside that works as a charge for storing energy. Unlike condensers, they use a single wire coil to amplify the signal that is picked up by the diaphragm.

A dynamic mic has a high gain level and is great for booming sounds and loud vocals. Dynamic microphones are great for live sounds because of their tough and rugged design.

They require almost zero maintenance and last almost a lifetime with normal use. On top of that, the rough and tough mic is very sturdy.

Although it is not ideally encouraged to drop your mic, regardless of how literally you take the term ‘mic-drop’, you may end up dropping your mic by accident during a stage performance. Even if you do so, it is unlikely to cause any damage to a dynamic mic thanks to its rugged construction.

Also, you won’t need phantom power to power your dynamic mic. And they are usually more cost-efficient than condenser mics.

Condenser Mics

Condenser-Microphone

Condenser microphones are best for capturing sounds that have high audio frequencies. Thanks to their thin diaphragms, condenser mics can pick up delicate and mild sound frequencies.

Condenser mics achieve this quality with the help of their lightweight diaphragm suspended by a fixed plate which tends to move whenever they are exposed to sound frequencies.

The pressure created by the sound waves on the diaphragm makes it move which in turn converts the acoustic energy of the sound waves into electric energy which is then stored inside the capacitor before being sent off to the recording device.

Sounds a bit complex, but the process is actually pretty simple.

The two drawbacks that condenser mics have are their fragility and the fact that they require an external power source. But that is only fair considering the amazing performance they give when it comes to studio recordings.

In fact, the added power is what gives them their high-output sound which is an unforgettable part of their characteristics.

Powering Condenser Microphones

Condenser mics require an external power source which is known as "Phantom Power." The most common source of this power is an active circuitry. Back in the old days, they were powered using huge external PSU boxes which were big and heavy and thus, not very efficient.

After that, the transistor technology took over. This allowed condenser mics to be powered directly from the mixing desk, without needing an external PSU box.

This saved up a lot of effort and hassle for the users. But the drawback to this was, that the phantom power consumed more energy than external PSU boxes.

Nowadays the ‘vintage’ tube technology is making its comeback, with a little bit of modification. Now they will produce the same warm acoustic sound without consuming much energy.

My Two Cents at the End

Now that you know pretty much everything there is to know about condenser microphones, you might be considering buying one based on your knowledge and research. Just remember that a good mic, although very important for producing a good sound, is not everything.

There are other factors like the sound card and the entire input-output setup. You need to find pieces of equipment that are the best match with that super expensive mic you have your eyes on.

Also, remember that a fancy price tag is not everything. Just because a mic costs more doesn’t mean that it would be good. Look for one that serves all your purposes ticking all the boxes including your budget. Always check and double-check, and you’re ready to roll.

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