An equalizer is just a volume knob for different pitches instead of for the whole sound. This page teaches you the whole thing from zero — and you can hear every concept as you read.
Sound is vibrating air. A speaker pushes air back and forth; that wiggle reaches your ear. Every sound is built from waves, and each wave has just two things that matter for EQ:
1. Frequency — how fast it wiggles, measured in Hertz (Hz) = wiggles per second. Fast wiggle = high pitch (a whistle). Slow wiggle = low pitch (a kick drum). This is the single most important idea on this page.
2. Amplitude — how big the wiggle is. Big wiggle = loud. Small wiggle = quiet. We measure loudness in decibels (dB).
That curve is a sine wave — the purest possible tone, one single frequency. Real sounds (a voice, a guitar) are hundreds of sine waves stacked together. EQ is how we turn the volume of those frequencies up and down independently.
Human hearing runs from about 20 Hz (a deep rumble you almost feel) to 20,000 Hz / 20 kHz (a thin "air"/sparkle, which fades as we age). EQ work is mostly about knowing what lives where on this map.
Because our ears hear in multiplications, not additions. The jump from 100→200 Hz sounds like the same musical distance (one octave) as 1000→2000 Hz, even though one is a 100 Hz gap and the other is a 1000 Hz gap. So every EQ display squashes the highs together: each time the frequency doubles, you move the same distance on screen. Keep this in mind — it's why the right side of an EQ always looks "crowded."
An EQ lets you boost (turn up) or cut (turn down) specific frequency ranges, without touching the rest. That's the entire concept.
Imagine a singer whose voice sounds muffled. The "muffle" usually lives in a specific range (~250–500 Hz). With EQ you reach in, cut just that range, and the voice clears up — while the bass and the sparkle stay exactly as they were. Or a guitar sounds dull: boost ~3 kHz and it cuts through the mix.
The line you draw across the spectrum is called the EQ curve (or frequency response). Flat line = "do nothing." A bump = boost. A dip = cut.
A band is one adjustable point on the EQ — one "handle" you grab to shape the curve. A real EQ gives you several bands so you can shape several regions at once. Each band has up to three controls:
Which part of the spectrum this band affects. Slide it left for bass, right for treble. This sets the center of the boost/cut.
How many decibels to boost (positive, curve goes up) or cut (negative, curve goes down). Zero gain = the band does nothing.
How narrow or wide the affected region is. Low Q = a wide, gentle hill that touches neighbouring frequencies too. High Q = a sharp, surgical spike that only hits a tiny range. (Q is short for "quality factor" — don't worry about the name.)
Bands come in different shapes, called filter types. Each is the right tool for a different job. Here are the ones you'll meet everywhere:
These six cover ~99% of real EQ work. The bell is your everyday workhorse; the two shelves handle broad tone shaping; high‑pass is used on almost every track ever recorded to clean out useless rumble.
You'll see EQs in two styles. Knowing the difference tells you what you're looking at instantly.
A fixed row of sliders (e.g. 10 or 31 of them), each glued to a preset frequency. You only control gain per band; frequency and Q are locked. Fast and visual — the row of sliders literally draws the curve. This is the "bass / treble" style you see on car stereos and the iPhone's built‑in EQ.
A few movable bands where you control all three: frequency, gain, and Q. Far more powerful and precise — you place a band exactly where the problem is. This is what pros use in studios, and it's what you'll drive in the next section.
There's also dynamic EQ and linear‑phase EQ — advanced variants — but master the parametric below and you understand them all.
This is the real thing. Pick a sound source, then drag the coloured dots on the graph to shape it. The white curve is what you're doing; the glowing teal shape behind it is the live spectrum of the sound — you can literally watch the EQ sculpt it.
| On | Band | Type | Freq | Gain | Q |
|---|
Tip: switch to Pink noise when learning — it contains every frequency at once, so any EQ move is instantly audible. Then load a song and try the same move; toggle bypass to A/B compare. Your ears improve fast doing this.
EQ in practice is a small set of repeatable moves. The presets above load these; here's why each one works so you can do them yourself.
High‑pass ~80 Hz (a voice has nothing useful below that — clears rumble), cut ~300 Hz a few dB (removes "boxy/muddy"), boost ~4 kHz (adds intelligibility & "in your face" clarity), gentle high‑shelf at 10 kHz (adds "air").
Mud lives around 200–500 Hz where many instruments pile up. A gentle wide cut there (low Q, ‑3 dB) instantly adds clarity to a cluttered track. The most useful move in all of mixing.
Boost the bass and the treble, leave the mids flat — the curve looks like a smile. Sounds exciting and "hi‑fi" on first listen, but overused it buries vocals. Great to recognise; use sparingly.
High‑pass at ~500 Hz and low‑pass at ~3 kHz together = only the narrow middle survives = instant "talking through a phone" sound. Shows how filters define a band by cutting everything outside it.
Got one annoying ringing frequency (feedback, a resonant cymbal)? Use a high‑Q narrow cut and sweep it until the annoyance disappears, then pull the gain down. Narrow + deep = surgical removal with minimal collateral damage.