Condenser Microphone : What it is and how to use it properly

This is for sure one the most desired equipments to have at your home recording studio. The condenser microphone is a transducer, just like any other microphone, meaning it transforms one type of energy into another. In this case it turns mechanic energy into electric energy; air sound wave into audio signal. However, some of the nuances it is able to capture are the main reason for its extensive use in voice recordings as much as of instruments in general. Besides, due to their reputation in the recording business, those are probably the most expensive microphones you will find. In this article we will talk about their characteristics and working.

In summary, what to expect from a condenser microphone?

• Need phantom power: Those microphones need external powering that normally comes from the interface or the sound board.
• High sensibility: Because of its active circuit and external power source, the condenser microphone captures very subtle sounds with significant gain.
• Quick transient response:  Its light and polarized capsule makes it a great microphone for short sounds (transients), keeping clarity of peaks.
• Rich in high and ultra high frequencies: On a good day we can say those microphones are "beautiful for detail", on a bad day we call them "a little too bright". But one thing is certain: condenser microphones are very accurate in capturing richness of detail in high end and nuances.

Introduction

A microphone is a transducer. Its function is to "translate" the sound pressure transmitted by air vibration into electric current variation. Microphones can be divided by their capsule construction style. These shapes are:

• Dynamic
• Condenser
• Ribbon

The condenser microphone generally has an embedded electronic circuit. This circuit can contain a tube or valve, like in guitar amps, for example (picture 1); transistors (being a solid-state mic); or even be an electret microphone. By design, condenser microphones have high transient response and a excellent response to high frequencies.

Inside a condenser microphone

Its capsule is composed of two thin metal plates, very close to each other. In physics, that is same characteristic of a capacitor, so that is why condenser microphones are also known as capacitor microphones. One of the plates is movable and behaves as a diaphragm, while the other plate (called backplate) is fixed. The moving plate is generally gold plated in order to conduct electrical current properly (figure 2). Both plates are connected to a converter that generates output tension. As in the illustration below: As the plate moves it creates electric potential difference - that difference is the signal captured being transmitted. However, this level of signal is very low and needs to be amplified. As we have seen, there is an internal circuit of the microphone, this circuit increases the gain of the signal and requires electrical power to work. The metal plates also need to be powered with electrical tension. That's why we need phantom power. Fun fact: electret condenser microphones require phantom power only for amplification. Their backplate is polarized by design.

Polar patterns on condenser microphones

We can have several different polar patterns. The most common are:

1. Cardioid - Picks up the sound from the front of the microphone. 
2. Hypercardioid - In this case it picks up sound in front and behind the microphone. Notice how the focus behind it is wider than in front.
3. Bidirectional - Picks up sound equally from the front or from behind. Notice that there is a rejection area in between both sides.
4. Omnidirectional - It picks up sound equally from any side.

Some models of condenser microphones only have one polar pattern. Other models have multiple patterns to choose from, therefore called multi-pattern.

Characteristics of a condenser microphone

High sensibility

The sensibility of a microphone is directly related to the voltage coming out of the capsule. The very high voltage output of condenser microphones makes necessary to have way lower gain on the preamp. A dynamic microphone usually needs a much higher gain.

High transient response

A transient is nothing more than a quick peak of energy - like a hit on the snare drum, a sole note with a pick on bass guitar or even a snap of fingers. Keep in mind that the volume of those three sounds is vey different, even if they are all played with the highest intensity possible. So what does high transient response means anyway? It means condenser microphones capture a lot more detail than any other microphones, because of the light structure of their diaphragm that moves easily even with low intensity sound sources. Due to the fast transient response and high sensibility to air flow and sibilance, it may ring a bell of what is a pop filter for. Use it in voice recordings!

Good response to high frequencies

High frequencies have less intensity than low frequencies. As we've seen on the previous topic, condenser microphones can represent those frequencies really well.

Need electric power

You need phantom power for the electronic circuit to work. Remember to connect the mic BEFORE turning the phantom power on! Make sure you never plug ANY microphone with the phantom power on, even if it isn't a condenser microphone! It can be provided by both an mixing desk or an audio interface. That's when you may need to find out what is an audio interface and understand why it's important to have one.

The condenser microphone is more fragile

Its construction is very delicate. If on one hand it is preferred for having a better performance, on the other, it demands extra careful handling because it's easier to break. It is also most important to avoid humidity when putting it away. There are cases of fungus growing inside microphones due to excess of humidity between the diaphragm and the backplate. (Note: If you find fungus on your microphone, it must be cleaned properly. That can only be done by specialists and authorized places. Doing it yourself might damage the microphone permanently. This process is usually a bit expensive).

Usage

With the advance of technology, microphone circuits have evolved as well. Manufacturers are now able to deal better with volumes above 120dB than they could years ago. Because of it the usage of condenser microphones is more varied than before, being largely found in recording studios everywhere. The richness of detail that condenser microphones are able to capture, puts them as favorites to record instruments with great dynamic variations, like acoustic guitars and drums, for instance.

Types of condenser microphones

Neumann U87

Created in 1960, it is very common in recording studios. Many world known artists have used it for singing.

• Big capsule.
• Balanced frequency through all the spectrum.
• Patterns: Omnidirectional, cardioid and figure 8.

AKG C414

Introduced in 1971, had suffered a lot of changes throughout history. The most drastic being the capsule ring. The factory has changed a metal ring for a nylon one and that made a few sonic changes in the microphone. Only in 1993 they revised it and it went back to the metal ring.

• Big capsule.
• Patterns: Omnidirectional, open and closed cardioid, hypercardioid and figure 8.
• The response is the same as it used to be with its own version.

Earthworks QTC50

• Small capsule.
• Omnidirectional pattern.
• Flat frequency response throughout the spectrum.
• Designed for sound sources with a lot of detail.

Beyerdynamic TG153

• Small capsule.
• Flat frequencies with more detail in high end.
• Cardioid pattern.

Neumann KMS104

• Cardioide or hypercardioid patterns.
• Condenser microphone with dynamic microphone performance.

Sennheiser e908

• Electret condenser microphone.
• Small and easy to handle.