What is a Condenser Microphone and When to Use One

If you’re looking into buying a microphone, then you’ve no doubt come across condenser microphones alongside dynamic mics and possibly even ribbon mics. You can, of course, use any of them to record audio, but what exactly is a condenser microphone and when should you choose to use one over its alternatives?

In this article, we’ll take you through the basics of how a condenser microphone works, the different types you will commonly come across, condenser vs dynamic microphones, and what recording applications they are useful in.

Simply put, condenser microphones are more sensitive than their dynamic siblings, and due to their design, are better at picking up more detail in a recording, with lower self-noise and better accuracy across a wider frequency spectrum.

With that said, this increased sensitivity comes with some disadvantages in certain recording scenarios. Condensers will generally pick up unwanted background sounds more readily, so aren’t as suited for use in spaces with lots of reflective surfaces or in particularly noisy environments. Also, condenser microphones are typically less rugged than dynamic microphones and may not be suited to applications like live performance, where they may be dropped or knocked around.

With these inherent characteristics, condenser microphones are best used in situations like studio recording (with some exceptions, which will be covered below) where you have a more controlled environment and require the best quality audio possible, but they may not be as appropriate in noisy rooms or loud stages.

Let’s take a closer look at what a condenser microphone is and when’s best to use one.

How Do Condenser Microphones Work?

Like every microphone, condenser mics utilise a sensitive conductive material (known as a diaphragm) that vibrates when sound waves hit it, which in turn induces a current in another element and creates an electrical signal.

In the case of condenser microphones, their capsule contains an extremely thin membrane of conductive material as its diaphragm, which is next to a solid metal plate that is charged with a current. When sound waves hit the sensitive diaphragm, it vibrates back and forth, transferring this current to the metal plate via induction and thus creating an audio signal.

The resulting signal doesn’t have a strong enough current to be output as is, which is why condenser microphones have an on-board preamp to boost it. This preamp – and in some designs, the charged metal plate as well – requires external power to function. In most modern, transistor-based microphones, this is supplied by 48V phantom power sent via the XLR cable used to connect the mic to a mixer or audio interface. Without this external power, condenser microphones cannot operate, so make sure your recording device can supply it and it is switched on when using one.

What are the Different Types of Condenser Microphones?

While we’ve covered the basic foundations of how a condenser microphone works, there are a few different approaches to the formula that further define mics in the category.

Large-diaphragm Condenser Microphone

Large-diaphragm condenser mics such as the RØDE NT1-A utilise a larger membrane in their capsule, as you may have guessed. While there isn’t necessarily an industry standard for what capsule size qualifies for this category, a condenser microphone with a diaphragm of 1 inch (25.4mm) or greater is considered a large diaphragm as a rule of thumb.

One of the biggest technical advantages of this design is that its larger diaphragm can generate a higher signal voltage, which in turn results in the microphone producing less of its own noise (self-noise).

Large-diaphragm condensers typically have a less consistent pickup pattern than small-diaphragm counterparts. While this may not be ideal if you're aiming for a perfectly uncoloured recording, it is what accounts for the ‘lush’ and ‘warm’ character often attributed to these microphones and is what makes them ideal for recording vocals, and in a range of other applications.

Small-diaphragm Condenser Microphone

Small-diaphragm condenser mics like the RØDE NT5 typically produce a flatter and less ‘coloured’ signal than their large-diaphragm counterparts, meaning they give you a very accurate audio image. They typically have an extended low- and high-frequency response, and a consistent pickup pattern that helps capture sounds as ‘naturally’ (or ‘neutrally’) as possible. This may or may not be ideal for you, depending on the recording application – for example, small-diaphragm condensers aren’t typically used to record vocals, but like many recording scenarios, it comes down to a matter of taste.

Just like their large-diaphragm brethren, there is no hard-and-fast rule for what qualifies as ‘small’, but it’s generally accepted that it refers to anything with a diameter of half an inch (12.7mm) or less. This smaller membrane also results in a superior transient response ideal for recording sound sources with a fast attack, like piano, drums and stringed instruments.

While almost all large-diaphragm microphones are side-address (meaning, you aim the sound source perpendicular to the microphone body), small-diaphragm mics can be either side- or end-address.

Tube Condenser Microphones

Tube condenser mics like the RØDE NTK utilise a vacuum tube (also known as a valve) in their preamplifier circuit rather than transistors. This style of microphone was the first to be developed amongst the condensers, but when transistor (also known as ‘solid state’) technology became widely available it largely replaced tubes due to the latter’s ‘imperfections’. These imperfections have since become revered for the character they impart, and tube mics have seen a resurgence over the past few decades.

Among the qualities of a tube microphone is that they tend to add pleasant harmonics to a sound source, as well as subtle saturation and compression. While this character can be desirable, tube mics also tend to come with a higher self-noise level and require a separate power supply to operate – 48V phantom power from your audio interface won’t cut it.

Shotgun Microphones

Shotgun microphones are a type of condenser mic distinguished by their long, tubular design. The purpose of a shotgun microphone is generally to record audio from a distance while maintaining focus and clarity.

In terms of differences in design from other types of condensers, the capsule is housed towards the back of the body in a shotgun microphone, with what is known as an 'interference tube' in front of it. This tube has evenly spaced perforations along its length (usually in the form of slits or, in the case of RØDE mics like the NTG5 and VideoMic NTG, circular openings). Sound waves enter through the front of the microphone, as well as from the side ('off-axis') via these perforations. This disrupts (or 'interferes' with) how the sound waves reach the capsule, resulting in these ‘off-axis’ sounds being filtered out through a process known as phase cancellation.

What does this actually mean in practical terms? Shotgun mics are very 'directional' microphones, meaning the audio they produce is very focused on what it is pointed at with excellent rejection of unwanted sounds from the side and rear. This makes them ideal for filmmaking applications when mounted on top of a camera or on a boompole, or studio applications where you need to isolate a sound source, such as foley work.

USB Condenser Microphones

The major point of difference for a USB microphone is the way the signal is output. Rather than an analog XLR connection, USB mics such as the NT-USB Mini feature a USB output and on-board A/D (Analog-to-Digital) converters for turning the electrical current produced by the capsule into a digital signal that can be sent directly to a computer or other digital recording device.

This makes them ideal if you’re after a simple, all-in-one solution for recording audio into your computer as there is no need for any extra equipment, such as an audio interface or mixer, and you generally just need a single cable to get up and recording. Most USB mics even feature a headphone output for directly monitoring your recording or for playback from your device.

What Are the Advantages of a Condenser Microphone vs a Dynamic?

Most microphones can be put to work in a wide range of situations, but some will flourish where others flounder due to their inherent traits. Let’s take a look at some of the key advantages when comparing condenser microphones to dynamic mics more generally.

1) They produce very accurate audio with a wide frequency response and low self-noise

As we’ve touched on, condenser microphones utilise a super-thin membrane as their diaphragm, which has a lower mass and is more responsive to sound pressure. As a result, they produce a more accurate representation of the sound source with lower self-noise, a wider frequency response, and better transient response (meaning fast-attack sounds like percussive hits and string plucks will be picked up more accurately).

2) They require less gain to achieve a good recording level

Because condenser microphones feature an internal preamplifier circuit, they have a stronger output than their dynamic counterparts, meaning they require less gain from an audio interface or mixer to achieve a good recording level.

3) They are more sensitive, making them ideal for recording at a distance

Another benefit of their design is that condenser microphones are more forgiving than dynamic alternatives when it comes to the proximity between the mic and your sound source. A condenser microphone will be able to pick up the sound more consistently and from further away than a dynamic mic, in turn resulting in a more balanced recording.

Typical Use Cases of Condenser Microphones

Most commonly, condenser microphones are used in the studio where their superior frequency and transient response, as well as their lower self-noise, are great for capturing clean, high-fidelity recordings that are true to the sound source.

While their increased sensitivity makes them more susceptible to picking up unwanted background noise, this is less likely to occur in a soundproofed studio. Similarly, the relative fragility of their design (at least, when compared to dynamic mics) isn’t as much of an issue in a controlled studio environment, nor is the possibility of unexpectedly loud sounds that could result in distortion in a recording.

While there are no hard rules on what instruments or sound sources you should record with a condenser microphone, they tend to excel in situations where you want to accurately capture every detail of the source. They are hugely versatile and typically what you’d call a 'workhorse' microphone as they can be used in a wide variety of recording applications, from recording vocals and spoken word to acoustic and electric guitar, drums, piano and more.

When to Choose Dynamic Over Condenser Microphones

While condenser microphones are useful in a wide range of situations, there are some common use cases where dynamic microphones are a better choice. If your recording environment lacks soundproofing or if there are a lot of competing sounds present (for example, in a live performance scenario), the higher sensitivity of condenser microphones means they may pick up these unwanted sounds. In these scenarios, a dynamic may be more suitable.

If you're planning on handling the microphone or moving around during recording, a dynamic will often be better as they are less prone to picking up handling noise – though in some cases this is accounted for with shock mounting, such as with shotgun microphones.

Condenser mics are also typically more fragile than dynamics, so aren’t ideal in recording situations where they are likely to experience a lot of movement or rough handling (although there are some exceptions – such as shotgun mics and condensers designed specifically for live performance, like the RØDE M2).

If the sound source you’re recording has the possibility of getting unexpectedly loud, then condenser microphones may not be ideal as they can distort at high volumes due to their sensitive nature and also may overload the input of your recording device due to their higher output level.

If you’re looking for a great condenser microphone, either large- or small-diaphragm, the RØDE range offers loads of excellent options for any recording application, including studio mics, on-camera mics, shotgun mics, live performance mics, USB mics and more.