Most microphones fall into one of two major categories: Condenser Microphones and Dynamic Microphones.
Condenser mics are incredibly sensitive and can offer rich, full-spectrum sound. But why are they called “condenser” microphones? And how exactly do they work?
What is a Condenser Microphone?
A condenser microphone uses two electrically charged metal plates to convert sound waves into electrical signals. One is a lightweight flexible diaphragm, which is suspended by the fixed back plate. These form a capacitor or condenser.
The thin diaphragm is incredibly sensitive, which allows it to pick up more detailed and subtle sounds. This makes condenser microphones ideal for recording studios and other controlled environments.
How Condenser Microphones Work
To understand how they work, you first need to know the basic parts of a condenser mic:
- Diaphragm: The thin membrane that vibrates when hit by sound waves.
- Back Plate: Found behind the diaphragm. It’s fixed and rigid.
- Amplifier: Charges the metal plates and runs the electrical signal to the audio device.
Condenser mics need electricity to power the front and back plates. As such, they require phantom power or another power source for the amplifier.
Once the amplifier has power, it sends an electrical charge to the diaphragm and back plate. This creates both positively and negatively charged electrodes in the air space between them.
Then, sound waves reach the diaphragm, causing it to vibrate. This creates pressure differences between it and the back plate.
As a result, the pressure differences change the capacitance (or voltage) between the two plates.
The voltage is extremely small and needs boosting before being sent to the recording device. So finally, the voltage gets sent back to the amplifier, which boosts the signal to a usable level.
Condenser Microphone Polar Patterns
Condensers are available with just about every microphone polar pattern:
- Cardioid — Picks up sound directly in front of the mic and rejects sound from behind.
- Supercardoid or Hypercardoid — Also picks up sound directly in the front. But it’s more narrow and better rejects sound from the sides.
- Omnidirectional — Picks up sound equally in all directions.
- Figure-8 — Picks up sound equally in the front and back, but rejects sound from the sides.
For more detailed explanations of each, check out our Microphone Polar Pattern Guide.
In their natural state, condenser microphones have an omnidirectional pickup pattern. To make them directional, little holes are punched into the back plate.
The holes delay the arrival of sound to the diaphragm’s back side. As a result, those frequencies get cancelled out, allowing the microphone to focus on only the desired sounds.
Some condenser microphones have switchable pickup patterns, either by a physical switch on the mic itself, or by replacing the capsule at the top of the mic.
Large Diaphragm vs Small Diaphragm Condenser Mics
Most condenser microphones fall into one of two categories: large- and small-diaphragm. Each one has its advantages.
Large Diaphragm Condensers
As a rule of thumb, a large diaphragm’s membrane has at least a 1-inch diameter. Sometimes it’s more or less, depending on the manufacturer.
Large diaphragm condensers came first in the 1930s and ‘40s. Historically, they needed to be big in order to overcome the noise of the tube electronics. The larger membrane can capture more acoustic energy, resulting in a higher signal voltage.
Noise performance is still the biggest technical advantage of a large diaphragm. Broadly speaking, they have lower self noise (static) than small diaphragm condensers.
Small Diaphragm Condensers
Small diaphragm mics are usually slim and have a pencil shape (hence the common name “pencil mics”). In general, the diameter of a small diaphragm is somewhere between .5 and .75 inches.
As for performance, small diaphragms have two main advantages over large diaphragms:
- Transient response — Smaller diaphragms can react to sound waves more accurately.
- Higher frequency response — The extended response allows them to pick up higher-frequency sounds, even those beyond human hearing.
Common Applications for Condenser Microphones
Condenser microphones are preferred when you want to capture more details from your sound source. They’re particularly useful in studio settings where you have more control over your environment.
Vocals
Condensers are great for capturing all the subtle details and nuances from singers and voice-overs.
Acoustic Guitars
Guitars have a natural resonance and produce lots of overtones. Condenser microphones help capture their sound with more detail and clarity. They also help emphasize the percussive sound of the strings.
Orchestral String Instruments
Like acoustic guitars, orchestral strings are highly resonant and produce plenty of overtones. Condenser microphones will help capture those extended frequencies.
Wind Instruments
Woodwind instruments are generally quieter than brass and percussion instruments. So you’ll want to use condenser mics due to their higher sensitivity. The extended frequency response also lets you capture their performance with more clarity and detail.
Drums
Engineers commonly use condenser mics as overheads for drum kits. This helps capture cymbals with better clarity and record the drum kit’s overall sound.
Large Groups & Ensembles
Condenser mics are commonly used to record choirs, orchestras, and other large ensembles as a group. Usually, you would place a stereo pair of microphones in front of the group.
Environmental Noise & Ambiance
Due to their extreme sensitivity, condenser mics are perfect for capturing a room’s natural noise. It could also be used to capture a room’s ambiance during a performance, like the reverberations in a concert hall.
Condensers are usually preferred for field recordings like nature sounds and other on-location audio.
Advantages & Disadvantages of Condenser Microphones
Dynamic microphones are incredibly useful. That said, they have some shortcomings to consider.
Condenser Mic Advantages
Excellent high-frequency response — Condenser microphones can capture upper harmonics in extreme detail.
Flatter frequency response — Condenser microphones usually have a flatter response without as many peaks and valleys.
Excellent transient response — They can more accurately capture and replicate a sound than other types of microphones.
Condenser Mic Disadvantages
More expensive — Broadly speaking, condenser microphones are more expensive than dynamic microphones.
Requires external power — Most require phantom power or some other external power source. If you don’t have one, you’re out of luck.
Inconsistent frequency response — The frequency response of a microphone usually changes depending on how close you are to the sound source. Low-cost models are particularly inconsistent.
Humidity and temperature — Environmental factors like humidity and temperature can negatively affect the mic’s performance.
Condenser vs. Dynamic Microphones
Without going into details, condenser microphones have a natural sound with a wider frequency response. That said, they’re super sensitive and tend to capture all room noise.
In other words, your big empty room will sound like a big empty room on a condenser mic. And that motorcycle driving by your house? You’ll hear that too.
Dynamic microphones have a narrower frequency range, but are generally better at rejecting room noise. They’re also better for close-miking loud sound sources.
For a deeper dive, check out our entry on dynamic microphones.
Which is Better? Dynamic or Condenser Microphones?
If you’re new to audio production and don’t have any sound treatment in your room, I generally recommend going with a dynamic microphone. They’re less likely to capture room noise and echos
But if you have proper sound treatment, a condenser microphone can capture audio in higher detail, giving you more to work with.
Sources:
- The Recording Engineer’s Handbook by Bobby Owsinski
- Modern Recording Techniques by David Miles Huber
- Neumann Microphones: What is the Difference Between Large and Small Diaphragm Microphones
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