What Is The Function Of A Condenser Microphone?

what is a condenser microphone?

a condenser microphone, also known as a capacitor mic, is a type of microphone that uses a lightweight, electrically charged diaphragm to capture sound with exceptional detail and accuracy.

a condenser microphone is a microphone that uses electrostatic, or capacitor, technology to convert acoustic energy into electrical energy. this type of microphone is also known as a capacitor microphone.condenser microphones are often used in recording audio because of their sensitive pickup of sound, but are sometimes utilized in live settings as well.

the british call them “capacitor microphones” – and for a reason, too. you may remember from physics class that a capacitor is essentially two metal plates in close proximity. the closer they are, the higher the capacitance.

• a microphone design in which the diaphragm is one plate of a capacitor and the back electrode is the other.
• it can either be externally charged or internally charged (electret microphone).
• a signal is generated whenever the diaphragm moves and the capacity is modulated.
• the capacity is typically in the range of 5-20 pf.
• a condenser microphone always has a built-in amplifier to support a robust signal run in cables.

how a condenser microphone works

the magic happens in the mic's capsule: a metalized diaphragm sits in close proximity to a metal backplate, creating a capacitor. when sound waves hit the diaphragm, the minute changes in distance between the diaphragm and backplate generate electrical signals that become your audio.

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.

1. sound waves are produced when something vibrates.
2. the vibrations cause the air molecules around the object to move.
3. microphones work on the same principle as our ears. they have a diaphragm that vibrates when it comes into contact with sound waves.
4. the vibrations are then converted into electrical signals that can be amplified and recorded.

a condenser microphone consists of two plates – one fixed and one moveable – that are separated by a thin layer of metal. the fixed plate is charged with a fixed voltage, and the moveable plate is connected to the ground. when sound waves hit the microphone, the moveable plate vibrates, which changes the distance between the two plates. this change in distance causes a change in capacitance, which is converted into an electrical signal.

when sound waves hit the diaphragm, it moves back and forth relative to the solid backplate. in other words, the distance between the two capacitor plates changes. as a result, the capacitance changes to the rhythm of the sound waves. voilà, we have converted sound into an electrical signal.

external power and signal output

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.

unlike its dynamic microphone cousins, a condenser mic requires electrical power to operate—either through phantom power or a dedicated power supply.

• condenser microphones therefore require external power.
• condenser microphones require external power for their internal electronics.
• 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.
• modern day tube condenser microphones, just like their ancestors, require an external power supply, because tubes consume more energy than phantom power is able to provide.

the capsule signal itself, however, is much too “fragile” to be connected to other pieces of gear. the condenser capsule’s output voltage is actually quite high, but it produces almost no current, because so little energy is stored in this small capacitor. it requires what is called an “impedance converter”, a circuit that buffers between the capsule and the outside world. the impedance converter makes the signal more “sturdy” by making more signal current available.

sound detail and sensitivity

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.

due to its extremely low mass, the diaphragm of a condenser microphone can follow the sound waves more accurately than that of a dynamic microphone with a (relatively) heavy moving coil attached. condenser microphones, therefore, offer superior sound quality. of all microphone types, condensers have the widest frequency response and the best transient response (transients are fast bursts of energy, e.g. the attack of a drum or the “pick” of an acoustic guitar). also, condenser microphones usually offer much higher sensitivity (i.e. output) and lower noise than dynamic microphones.

• they capture the most delicate sounds with incredible precision
• excellent at capturing a wide range of frequencies
• quick to react to sudden sound changes
• suitable for multiple recording applications

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).

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.

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.

large diaphragm condenser microphones

not all condenser microphones are created equal. the size of the diaphragm plays a crucial role in the mic's character and performance.

typically featuring a diaphragm around 1 inch (27 mm) in diameter, large diaphragm condensers are a favorite for:

• capturing distant or quiet sources
• vocal recordings
• room microphones
• creating a warm, rich sound

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 microphones

with diaphragms around 1/2 inch (typically 12-13 mm), small diaphragm condensers excel at:

• capturing spread-out sources like orchestras and choirs
• high-end sources like pianos and strings
• providing a more natural, accurate sound

small-diaphragm condenser microphone 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.

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.

common recording applications

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 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.

• condenser microphones are commonly used for studio vocals, acoustic instruments, drum overheads, room mics, pianos, and any application where detail, realism, and extended frequency response are essential.
• whether you're recording lead vocals, backing vocals, or voiceovers, condenser microphones provide the clarity and detail needed to capture the human voice in all its nuances.
• condenser mics are often used as overhead mics for drum kits, capturing the cymbals and overall ambiance of the drum set.
• they can also be used for specific drum pieces like the snare or toms.
• the sensitivity of condenser microphones makes them ideal for recording acoustic instruments, such as guitars, where capturing the natural resonance and overtones is essential.
• small diaphragm condenser mics are commonly used in field recording to capture ambient sounds, nature sounds, or on-location audio for film and video production.
• usb condenser microphones offer a convenient solution for podcasters and broadcasters, providing plug-and-play functionality without the need for additional equipment.
• while not as common as dynamic microphones for live sound, condenser mics are sometimes used for live performances, especially when a more detailed sound capture is desired, such as with choirs or orchestras.
• in professional studio environments, large diaphragm condenser mics are favored for their ability to capture a wide frequency response and subtle sonic details, making them a go-to choice for many producers and sound engineers.

limitations in noisy or loud environments

with 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.

• 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.
• 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.
• 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.
• they can be too sensitive for live situations; sensitive microphones can sometimes cause feedback in live sound settings.