Parametric EQ

By Dan Murtagh · Updated

Short answer: a parametric EQ lets you set three things on each band: where it works (frequency), how much it boosts or cuts (gain) and how wide it is (Q). A graphic EQ gives you fixed bands you can only turn up or down. The EQ that comes with your DAW is almost certainly parametric.

A bell band on a full mix or pink noise. Move frequency, gain and Q, and flip EQ off and on. The EQ side plays at the same loudness as the clean side, so what changes is the tone, not the volume. Switch Match levels off to hear how much louder a boost makes it.

The three controls

  • Frequency is where the band works: the centre of the bell, in hertz (Hz). Low numbers are bass, high numbers are treble. People hear from about 20 Hz to 20 kHz.
  • Gain is how far it turns that range up or down, in decibels (dB). Plus is a boost, minus is a cut.
  • Q is how wide the band is. A low Q is broad: at Q 0.7 the band covers about two octaves. A high Q is narrow: at Q 4.3 it covers about a third of an octave. At Q 1.4 it’s about one octave.

A bell band (also called a peak or peaking band) is the shape you get: flat, then a hill or a dip around the frequency, then flat again. Most parametric EQs also give you shelves and filters at the ends. They have their own pages: shelving EQ and high-pass and low-pass filters.

How to hear each one

Frequency

Set a big boost, +9 dB at a medium Q, and slide the frequency slowly from left to right. On the full mix the boost moves from the kick and bass, through the body of the instruments, into honk, then bite, then the hiss of the cymbals. That one sweep is the whole range an EQ works on. It’s also how engineers find a problem: boost, sweep, and listen for the spot where it jumps out.

Gain

Pick a frequency and flip EQ off and on at +3, +6 and +9 dB. Then try the same amounts as cuts. Small moves are harder to hear than you’d think, which is why the flip matters: you compare, you don’t guess.

Q

Keep the frequency and gain where they are and change only the width. Wide sounds like a change of tone. Narrow sounds like one note ringing, or a whistle. Try Wide, then Narrow, on pink noise: the difference is easy to hear there.

Why a boost fools you

When two versions differ in level, the louder one usually sounds better. A boost makes the sound louder, so it tends to win the comparison whether or not the tone is better. That’s why the demo matches levels: the EQ side is turned down by as much as the boost made it louder, and the readout shows by how much. Switch Match levels off and the boost jumps out.

Do the same in a session. Before you judge a move, match the output level of the EQ to the bypassed sound. Many EQ plug-ins have an output gain, and some have an automatic one.

When to use it

  • A ring or resonance: find it with a narrow boost and a sweep, then turn the boost into a cut of the same width.
  • A change of tone: a wide band with a few dB of gain. Wide moves sound more natural than narrow ones.
  • A rule of thumb many engineers use: cut narrow, boost wide. A narrow boost tends to sound like a whistle; a narrow cut can take out one problem and leave the rest alone.

Questions

What does Q mean on an EQ?

Q is the width of a bell band. The higher the Q, the narrower the band. At Q 1.4 a band covers about one octave, at Q 0.7 about two, and at Q 4.3 about a third of an octave. Plug-ins measure Q in slightly different ways, so the same number can sound a little different from one EQ to the next. Trust your ears over the number.

What’s the difference between a parametric EQ and a graphic EQ?

A graphic EQ has fixed bands, usually one slider each, at fixed frequencies and widths. A parametric EQ lets you set each band’s frequency, gain and Q. A semi-parametric EQ lets you set frequency and gain but not Q.

What is a good Q setting?

It depends on the job. For a broad change of tone, somewhere around 0.5 to 1.5. For taking out one ring or resonance, 5 or higher. Start wide, and narrow it only if the move is changing things you want to keep.

Is a parametric EQ pedal the same thing?

The controls are the same. A pedal puts a parametric EQ in front of a guitar amp; this page is about the EQ in a mixing plug-in or on a console channel.

Train it

Hear where a boost sits, then undo one.

Sweep hides a boost in the sound and you slide a band until you find it, against the clock. Restore changes the sound with one bell band, and you put it back with a band of your own: frequency, gain and all.

Train it in Sweep

Then: Restore · Free, in your browser, no account