Soundware Beginners Guide to...
A couple of good quality microphones are a useful addition to any home studio setup. If you’re trying to improve the sound of your recordings, a better microphone will probably provide you with the most obvious sound quality improvement for your money – there’s really no point in spending hundreds of pounds on preamps and cabling only to connect it all to the cheapest mic you can find.
It’s also always worth taking a critical look at your mic placement technique – even top of the range, pro quality microphones can produce very poor results if placed incorrectly. Conversely, relatively inexpensive microphones can give surprisingly good results if positioned carefully.
There are a number of different types of microphone to choose from. If you are unsure which would be best for you, please contact us and we will be happy to help.
Types of Microphone:
- Polar Patterns
- Frequency Response
- Equivalent Noise Level
- Maximum SPL
- Phantom Power
- Close Miking
- Stereo Techniques
Types of Microphone:
DynamicDynamic microphones are the simplest in design, and are the type with which most people are familiar. A wire coil is attached to a diaphragm, which vibrates when sound waves hit it. A magnet fixed inside the coil causes an alternating electrical current to be created in the wire (because of the “Motor Effect”), which is proportional to the strength and frequency of the original sound waves.
Because dynamic microphones are so simple, they’re also very robust which makes them ideal for live sound. In the studio this makes them useful for recording very loud sounds, such as guitar amps and drums, that could damage more sensitive microphones. However, they’re often not sensitive enough to record quieter, more subtle sounds such as acoustic guitars, classical instruments or vocals.
Examples of Dynamic Microphones:
Behringer Ultravoice XM8500
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CondenserCondenser (sometimes called capacitor) microphones work in a slightly different way to dynamic mics. Instead of a coil and magnet, a capacitor is made up of two plates with opposing electrical charges. One of these plates is moveable and acts as the diaphragm, and one is fixed. The opposing charges create a voltage across the capacitor, which changes depending on how close together the plates are. So, when sound waves hit the diaphragm, it moves and a voltage proportional to the sound waves is created.
Condenser microphones give a much more detailed sound signal than dynamic mics, and are the most commonly used in studio situations for recording acoustic instruments and vocals. However, they are easily damaged and so are not suitable for recording very loud sounds. Condenser mics also require extra power to provide the electrical charge in the capacitor plates, known as phantom power.
Condenser microphones vary in their diaphragm size. Large and small diaphragm condensers have different qualities and as such are used for recording different sounds. Large diaphragm condenser mics are generally more sensitive, but because of this are more fragile. They also “colour” (or reduce the quality) of sound coming “off-axis” (outside their pickup area). They are generally used for solo vocal recording. Small diaphragm condensers are less sensitive, but are more robust and do not colour off-axis sound as much. They are useful for recording acoustic guitars or classical instruments, and are often used in pairs for ambient stereo recordings of groups of instruments, for example a string quartet or vocal ensemble.
Examples of Small Capsule Condensers:
Samson C02 - Sold as a pair
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Examples of Large Capsule Condensers:
M-Audio Solaris - Large-capsule condenser with variable polar patterns.
Samson CO1U - USB bus-powered large-capsule condenser.
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Polar PatternsThe polar pattern of a microphone is the area over which it will pick up sound. Different polar patterns have different uses – for example, cardioid microphones, which pick up sound coming from one side only, are useful for live work as they reduce the risk of feedback, or for reducing spill between microphones when several musicians are being recorded at once. An omnidirectional microphone, on the other hand, picks up sound from all sides and so would be more useful for capturing room ambience. Some common polar patterns are shown below:
Frequency ResponseThe frequency response of a microphone states how well the microphone picks up different frequencies (or "pitches") of sounds. This is useful to know, since a microphone with excellent low frequency response but next to no high frequency response would be very useful for recording a kick drum but would not be suitable for a vocal recording. Frequency responses are usually plotted on diagrams that show the strength with which the microphone will pick up sounds of different frequencies, or are sometimes stated as a frequency range such as “20Hz-20kHz”. Although this does not give as much information as a frequency response diagram, it can give an idea of the microphone’s sensitivity to high or low frequencies.
Equivalent Noise LevelThe equivalent noise level tells us how much noise the microphone adds to a sound (usually a background hiss or hum). This is measured in dBA (decibels, weighting method “A”) or in dBA-weighted (a slightly different way of measuring how the ear perceives loudness, which will give readings about 12dBA higher than an unweighted measurement). Generally, the lower the equivalent noise level the better. This is especially important when recording quiet sounds like acoustic guitars or vocals.
Maximum SPLThe maximum SPL (sound pressure level) tells us how loud a sound a microphone can pick up without distorting. The higher the better.
Phantom PowerCondenser microphones need their own power source to provide the electrical charges in the capacitor plates. Some condenser mics will run off batteries, but most require phantom power. This is an additional 48V power supply provided through the microphone lead from the mic input. Many mixers and microphone preamps have phantom power supplies built in, but these are also available separately.
Microphone TechniqueNo matter how expensive a microphone you’re using, if it’s not correctly positioned to record a sound it won’t produce a professional result. Ultimately, the best way to be sure you’ve positioned a mic correctly is to spend time experimenting with different placements until you find one you like, but there are some standard methods that act as a good starting point.
Close MikingClose-miking is the most commonly used microphone placement technique in modern pop music. The technique quite simply involves placing a microphone as close to an instrument as possible to eliminate outside noise and ambience. Because this typically gives a very dry sound, reverb is usually added to the sound at a later stage. To close-mic an instrument it’s important to consider how the instrument produces sound and where it comes out, so that the mic can be placed at the optimum point to pick up the sound. Different microphone placements can produce a variety of different sounds on the same instrument; a mic placed at the neck joint of an acoustic guitar can produce a very sweet, mellow tone, for example, or can be moved nearer to the bridge for a brighter sound. Or two microphones can be used, one over the bridge and one over the neck joint, and their relative volumes adjusted to give a blend of the two different tones. These techniques can be varied infinitely, and as such can give the engineer a lot of creative control over the sound of a finished recording.
Ambient MikingAmbient miking differs from close miking in that, rather than choosing a specific mic placement for the tone it gives, its purpose is to produce as accurate a representation of the original sound as possible. Mics are usually placed further away from the instruments to pick up reverberations and background noise. Ambient recordings are also often recorded in stereo, using two microphones panned left and right, as this gives the listener a much more accurate impression of the sound and allows them to gauge where instruments were placed in relation to each other during the recording.
Stereo TechniquesThere are many placements for a pair of microphones when recording in stereo. Here are a few standard techniques:
In the coincident microphone placement technique, the two microphones are placed one on top of the other, almost touching. The microphones face in towards each other, so that each microphone is pointing to the opposite side of the ensemble being recorded.
In the near-coincident technique, the microphones are angled away from one another, so that the two microphones are pointing at the left and right edges of the sound source.
ORTF stands for "Office de Radiodiffusion-Television Francaise". It is a variant of the near coincident placement used by the French National Broadcasting Organisation, where the microphones are placed exactly 17cm apart and at an angle of 110 degrees to each other.
The spaced pair technique uses two microphones placed parallel to one another, pointing directly at the sound source. The space between the microphones can be varied, but the two microphones should always be the same distance from the centre of the sound source.