Microphones

A microphone turns air pressure into an electrical signal. Different designs do that in different ways, and each one colors the sound. Picking the right mic, and pointing it the right way, matters more than any plugin you add later.

How a Microphone Works

Every mic has a diaphragm: a thin, light surface that moves when sound waves hit it. The mic turns that movement into a small voltage. How it does that defines the three main types: dynamic, condenser and ribbon.

The signal coming out of a mic is very quiet (called mic level). It needs a preamp to raise it to line level before it reaches your audio interface's converter. Most audio interfaces have preamps built in.

The Three Main Types

Dynamic microphones

A dynamic mic has a diaphragm attached to a small coil of wire sitting in a magnet. When the diaphragm moves, the coil moves, and that creates a voltage (the same principle as a speaker, in reverse).

• Tough, cheap to make and don't need power.
• Handle very loud sources (guitar amps, snare drums, kick drums) without distorting.
• Less sensitive, so they pick up less room sound. Great for untreated home studios.
• Need more preamp gain, and capture less high-frequency detail than condensers.

Condenser microphones

A condenser mic uses a very thin diaphragm placed close to a metal backplate. Together they form a capacitor. Sound changes the gap between them, which changes the voltage. Condensers need power to work, usually phantom power.

• Very sensitive and detailed, with a strong high-end response.
• The studio standard for vocals, acoustic guitar, piano and overheads.
• Pick up more room sound and background noise, so the room matters.
• More fragile than dynamics.

Condensers come in two main sizes:

• Large-diaphragm condensers (LDC, about 1 inch / 25 mm): warm, flattering and slightly larger than life. The classic vocal mic. Usually side-address: you sing into the side, not the top.
• Small-diaphragm condensers (SDC, often called "pencil" mics): accurate, with fast transient response. Used for acoustic guitar, overheads, hi-hats and stereo pairs. Usually end-address: you point the end at the source.

Ribbon microphones

A ribbon mic uses a very thin strip of corrugated metal suspended in a magnetic field. Ribbons are known for a smooth, warm, slightly dark top end that tames harsh sources like bright guitar amps, brass and drum overheads.

• Naturally figure-8 (they pick up front and back equally).
• Fragile: a strong blast of air can stretch the ribbon. Never blow into one.
• Low output, so they need a quiet preamp with lots of gain. Some modern ribbons are "active" and use phantom power to boost their output.

Polar Patterns

A polar pattern shows how sensitive a mic is from each direction. Picture the mic in the center, pointing up. The coral shape shows how much sound it picks up from each angle: the further the line from the center, the more sensitive.

Many large-diaphragm condensers are multi-pattern: a switch lets you choose omni, cardioid or figure-8.

Phantom Power (+48V)

Phantom power is a DC voltage, usually +48 V, that your interface or mixer sends up the XLR cable to power a condenser mic. It's called "phantom" because it travels on the same wires as the audio, with no extra cable. The button is usually labeled 48V or +48V.

• Condenser mics and active ribbons need it.
• Dynamic mics ignore it, so it's safe to leave on for them with a normal balanced cable.
• Turn your monitors down before switching phantom power on or off. It can cause a loud pop.
• On many budget interfaces, one 48V button powers several inputs at once.

Proximity Effect & Frequency Response

Proximity effect

The proximity effect is a boost in bass that happens when you get close to a directional mic (cardioid, supercardioid or figure-8). The closer you get, the bigger the boost. Within a few centimeters it can add many dB below about 200 Hz. Omni mics have little or no proximity effect.

• Use it: radio presenters and singers work close to sound warm and intimate.
• Fight it: if a vocal sounds boomy, back the singer off a little or use the mic's low-cut (high-pass) switch, often at 80 or 100 Hz.

A high-pass filter removes rumble and extra low end below its cutoff. Try it on the demo below.

Frequency response

A mic's frequency response chart shows how strongly it picks up each frequency. A "flat" mic treats all frequencies equally. Most vocal mics have a presence peak, a boost somewhere around 3–8 kHz that helps words cut through. The Shure SM57 and SM58 have a noticeable presence rise in this range, which is part of their familiar sound.

Other specs worth knowing:

• Sensitivity: how much output the mic gives for a given sound level. Condensers are far more sensitive than dynamics.
• Self-noise: the hiss the mic makes on its own. Lower is better for quiet sources.
• Max SPL: the loudest sound (in dB SPL) it can handle before distorting.

Famous Microphones

USB vs XLR

Some mics offer both USB and XLR outputs, which is a flexible middle ground. For a full home setup, see Home Studio Setup.

Accessories: Pop Filters & Shock Mounts

• Pop filter: a mesh screen (nylon or metal) placed between the singer and the mic. It breaks up bursts of air from plosives ("p" and "b" sounds) that would otherwise hit the diaphragm and cause a low thump. Place it about 5–10 cm from the mic.
• Shock mount: a cradle of elastic bands that holds the mic and isolates it from vibrations traveling up the stand (foot taps, desk bumps, traffic rumble).
• Windscreen (foam cover): reduces wind and breath noise. Essential outdoors.
• Reflection filter: a curved panel behind the mic that reduces some room reflections. It helps, but it's not a replacement for treating the room behind the singer.
• Cables and stands: a solid stand and good balanced XLR cables prevent many mysterious hums and crackles.