Recording

Microphones: which one, and where to put it

7 min read

A microphone is the only part of the chain that has to physically touch the sound. That makes it special, and it is why microphone shopping is so full of confident nonsense. Here is a way to think about it that actually helps.

The three kinds

Dynamic microphones pick up sound through a coil and a magnet, and they are rugged, forgiving and good at rejecting things they should not hear. They handle loud sources comfortably — a guitar amp, a snare drum, a loud singer. They need less preamp gain. They are the right default for an untreated room.

Condenser microphones use a thin diaphragm that changes capacitance as it moves. They are far more sensitive and far more detailed, and they pick up the room as faithfully as they pick up the source. That is wonderful in a good room and disappointing in a bad one. They need phantom power. They are the right default for a treated room and a quiet source.

Ribbon microphones are a passive kind of dynamic with a very thin, delicate ribbon. They are the smoothest-sounding option and they are also fragile, they need plenty of gain, and they can be damaged by phantom power. They are a luxury for most home studios and a revelation for those who get one.

The best microphone in the wrong room loses to the cheapest microphone in the right room. This is not a slogan; it is just how sound works.

USB versus XLR

A USB microphone plugs into the computer and contains its own preamp and converter. An XLR microphone needs an interface.

USB microphones make sense when:

You are recording voice only and want the simplest possible setup.
You are starting out and have not decided whether to buy an interface.
You want to record on a laptop away from your desk.

They are less good when:

You want to run the microphone into an interface with proper preamps.
You want to record a microphone and an instrument at the same time.
You want a real analog signal path, or you want the flexibility to change microphones later.

One important trap: a USB microphone with a headphone jack is not a monitor. The headphone output on most USB microphones lets you hear yourself, but it lags behind the input by the round-trip latency of the conversion. Recording while playing to those headphones is genuinely difficult, because you are hearing yourself late. If you plan to record and play at the same time, use an interface with proper monitoring, not a USB microphone's headphone socket.

Choosing one microphone

Work through these questions in order:

What is the loudest thing you will record? A quiet voice, a loud guitar amp, a snare drum, or nothing at all. If anything is loud, use a dynamic microphone. There is no point owning a large-diaphragm condenser if your source will damage your ears or the mic.
Is the room treated? If not, use a dynamic. A dynamic's rejection of room sound is the single most useful property for a beginner.
Do you have a quiet room? If the room is noisy, a microphone with a tight polar pattern — cardioid — rejects more of the room than an omnidirectional one. Dynamic cardioid microphones are ideal here.
Do you need to hear yourself while playing? Yes, so buy headphones, and ideally a microphone that works with an interface rather than a USB one.

A good starter microphone for most homes is a cardioid dynamic: a broadcast-style microphone such as an SM58-class model for speech and vocals, or a slightly larger dynamic with more presence for music.

Where to put it

Placement matters more than the model, and it costs nothing to change.

Distance. Sound level falls by about 6 dB every time you double the distance. Moving from 10 cm to 20 cm is a 6 dB drop; to 40 cm is another 6 dB. Closer is louder and more intimate, but captures more room and more mouth noise. Farther is quieter and drier. For vocals, 15 to 20 cm from the singer's mouth is a good starting point.

Off-axis position. Point a cardioid microphone slightly away from the source, just off the axis of the loudest sound. This reduces plosives and sibilance without losing much body. A common mistake is to aim the microphone straight at the mouth, which produces a "p" and "s" sound that no amount of editing fixes convincingly.

Height. Put the microphone at mouth height for speech. For instruments, aim at the part that sounds best rather than at the loudest part.

Angle versus distance. Two microphones of the same model at different angles can sound completely different. The one aimed slightly off-axis will usually be more forgiving.

The supporting cast

These matter more than people expect:

A pop filter. Every vocal recording needs one. A filter with a distance of about 15 cm, mounted between the microphone and the singer, removes the plosive burst before it becomes a permanent problem. They cost almost nothing and save every take.
A shock mount. It stops structure-borne sound — footsteps, chair creaks, desk knocks — from travelling through the microphone body into the recording. Essential for acoustic instruments, and worthwhile for voice.
A decent stand. A heavy stand with a good boom arm. A wobbly stand puts a low rumble into every take, and it is easy to mistake for a room problem.
Balanced XLR cables. Keep spares. Buy good ones once.

Getting the level right

Set the preamp so that the loudest moment of the performance peaks around -12 dBFS.
Watch the meter, not the knob. A peak LED that lights occasionally is fine; a peak light that stays on is not.
If the source is too quiet and you run out of preamp gain, you need a different microphone or a different source level — not more gain.
If you clip, lower the preamp and do the take again. Clipping is not recoverable.

Recording two sources at once

One microphone per source, each on its own input, each with its own preamp setting. If a quiet source and a loud source share a gain setting, one of them will be wrong. Set each gain independently and keep them there.

Remember that the microphone closest to the loud source will pick up the quiet source too. If you are recording a guitar and a voice together, you will hear the guitar in the vocal microphone — which is why separate takes, or a headphone mix, are often cleaner than a single take.

A quick microphone test

Before you trust a new microphone, do this:

Speak at a normal distance, then at arm's length. The level should drop smoothly by roughly 6 dB each time you double the distance.
Clap once, sharply. A good microphone will not distort at reasonable gain.
Touch the microphone body. You should hear structure-borne noise, and the shock mount should stop it.
Speak into the back of the microphone. A cardioid pattern should reject it strongly. If it does not, you have the wrong end facing you.
Record a minute of the room in silence. That noise floor is the floor of every recording you will make with this microphone — now you know what you are working with.