Equalization (EQ)
EQ is the most-used tool in mixing. It turns specific frequencies up or down, so every part gets its own space. Learn the band types, the three controls, and a few reliable moves, and you can fix most mud, boom and harshness.
What EQ Does
An equalizer (EQ) is a volume control for a specific range of frequencies. Instead of making the whole sound louder or quieter, it changes only part of the spectrum: the boom of a kick, the boxiness of a vocal, the fizz of a guitar.
You use EQ for two main jobs:
- Corrective EQ: remove problems like mud, rumble, ringing or harshness.
- Creative / tonal EQ: shape character, like adding air to a vocal or weight to a snare.
You learned the frequency regions in What is Sound?. EQ is where you put them to work.
Gain, Frequency and Q
Every EQ band has up to three controls:
- Frequency: the center (or corner) of the band, in Hz.
- Gain: how much to boost (+) or cut (−), in dB.
- Q (or bandwidth): how wide the band is. A low Q (0.5–1) is wide and musical. A high Q (5–10+) is narrow and surgical.
Our ears are very sensitive to small changes, especially in the upper mids (2–5 kHz). A 2–3 dB move is often plenty. If you need more than about 6 dB, ask whether you chose the wrong sound in the first place.
Band Types
| Band type | Shape | What it does | Typical use |
|---|---|---|---|
| High-pass (low-cut) | ⟋‾‾‾‾ | Removes everything below the cutoff | Clear rumble from vocals, guitars, pads |
| Low-pass (high-cut) | ‾‾‾‾⟍ | Removes everything above the cutoff | Tame fizz, push sounds back in the mix |
| Low shelf | ‾‾╲____ | Raises or lowers everything below a point by a fixed amount | Add weight to a bass, reduce boom |
| High shelf | ____╱‾‾ | Raises or lowers everything above a point | Add "air" to vocals, darken cymbals |
| Bell (peak) | __╱╲__ | Boosts or cuts a band around a center frequency | Remove mud at 300 Hz, add presence at 3 kHz |
| Notch | ‾‾‾V‾‾‾ | Very narrow, deep cut | Remove a ringing tone, hum at 50/60 Hz |
High-pass and low-pass filters have a slope, measured in dB per octave: 12 dB/oct is gentle, 24 dB/oct or 48 dB/oct is steep. You met these in Filters.
Subtractive vs. Additive EQ
Subtractive EQ means cutting frequencies you don't want. Additive EQ means boosting frequencies you want more of. A common rule is "cut narrow, boost wide":
- Cut problems with a narrower Q (2–8), because problems usually sit in a small area.
- Boost with a wide Q (0.5–1.5) or a shelf, because wide boosts sound natural.
Cutting is usually safer. It frees up space for other parts and doesn't raise the level toward clipping. But don't be afraid to boost: a gentle high-shelf on a vocal is one of the most common moves in modern pop.
Sweep and Cut
How do you find the exact frequency of a problem? Use the sweep-and-cut technique (also called "boost and sweep" or "seek and destroy"):
- Create a bell band with a narrow Q (about 5–8).
- Boost it a lot:
+10 to +15 dB. - Slowly sweep the frequency across the range while the track plays.
- When the problem jumps out (ringing, boxy, harsh), stop.
- Turn the boost into a cut of
-3 to -6 dB, then widen the Q until it sounds natural.
A huge narrow boost makes every frequency sound bad. Only cut what still sounds like a problem when you bypass the boost and listen again. Turn your monitors down while sweeping; big boosts get loud fast.
Instrument Frequency Cheat Table
These are common starting points, not rules. Every recording is different, so always listen before you cut.
| Instrument | Weight / body | Mud / box | Presence / attack | Air / sizzle |
|---|---|---|---|---|
| Kick | 50–100 Hz | 200–500 Hz | 2–5 kHz (beater click) | — |
| Bass / 808 | 40–100 Hz | 200–400 Hz | 700 Hz–2 kHz (growl, string noise) | — |
| Snare | 150–250 Hz | 400–800 Hz (boxy) | 2–5 kHz (crack) | 6–10 kHz (snares, sizzle) |
| Vocals | 100–250 Hz | 200–500 Hz | 2–5 kHz (clarity); sibilance 5–9 kHz | 10–16 kHz |
| Acoustic guitar | 80–200 Hz | 200–400 Hz | 2–5 kHz (pick attack) | 8–12 kHz |
| Electric guitar | 100–250 Hz | 300–600 Hz | 1.5–4 kHz (bite) | Little useful above 8 kHz |
| Hi-hats / cymbals | — | Below ~300 Hz (bleed) | 3–6 kHz | 8–16 kHz |
| Piano / pads | 80–200 Hz | 200–500 Hz | 1–4 kHz | 8–12 kHz |
For a full chart, see Frequency Chart.
Carving Space for Kick and Bass
Kick and bass share the low end, and they're the most common clash in modern music. Give each one its own zone:
Kick vs. bass carving (one approach)
Decide which one owns the sub. In house and techno, the kick often owns it. In trap, the 808 usually owns it and the kick is shorter and punchier. You can also duck the bass when the kick hits; that's covered in Sidechain & Ducking.
High-pass (almost) everything
Many sounds have low-frequency energy they don't need: vocal rumble, guitar boom, pad low end, hi-hat bleed. Removing it with a high-pass filter leaves more space for kick and bass.
Don't high-pass on autopilot at 100 Hz. Cutting too high makes a mix thin, and dozens of gentle high-passes can add up. Set the cutoff by ear: raise it until the sound changes, then back off. Typical starting points: vocals 80–120 Hz, guitars 80–100 Hz, hi-hats 200–400 Hz, pads 100–200 Hz.
The EQ control that sets how wide a band is, is called .
A filter that removes everything below its cutoff is a filter.
Advanced EQ Concepts
Minimum phase vs. linear phase
Most EQs are minimum phase. They work like analog EQs: changing a band also shifts the timing (phase) of frequencies near it a little. This is usually fine and often sounds natural.
A linear phase EQ keeps all frequencies perfectly in time. It's useful when you EQ several tracks of the same source (like multi-miked drums) or in mastering. The costs: more CPU, added latency, and pre-ringing, a soft "pre-echo" before sharp transients, especially with steep low-frequency cuts. Use minimum phase by default, and linear phase when you have a reason.
Dynamic EQ
A dynamic EQ band only cuts (or boosts) when that frequency gets louder than a threshold. It works like an EQ and a compressor combined. Use it for problems that come and go: a vocal that gets harsh only on loud notes, or a bass note that booms on one pitch. A de-esser is a type of dynamic EQ aimed at sibilance (5–9 kHz).
EQ before or after compression?
- EQ before the compressor: cut problems (rumble, boom) first, so the compressor doesn't react to them.
- EQ after the compressor: tonal boosts, so the compressor doesn't fight them.
A common chain is: high-pass and corrective cuts → compressor → tonal boosts. Learn more in Compression.
- Add an EQ to a vocal or synth (Ableton: EQ Eight, FL Studio: Fruity Parametric EQ 2, Logic: Channel EQ).
- Enable a high-pass band. Raise the cutoff until the sound gets thin, then back it off by about a third.
- Use sweep-and-cut to find a boxy or harsh spot. Cut it by 3 dB.
- Add a wide high shelf at 10 kHz, +2 dB, for air.
- Bypass the EQ while the full mix plays. If you can't hear an improvement in context, undo it.
1. Which EQ band type is best for removing a narrow ringing tone?
- Low shelf
- High shelf
- Notch
- Low-pass
A notch is a very narrow, deep cut, ideal for one ringing frequency or hum.
2. What does a high Q value mean?
- A narrow band
- A wide band
- A bigger boost
- A steeper filter slope only
High Q is narrow and surgical; low Q is wide and gentle.
3. In the sweep-and-cut technique, what do you do after finding the problem frequency?
- Leave the boost in place
- Add a high shelf
- Delete the track
- Turn the boost into a moderate cut and widen the Q until it sounds natural
The big boost is only for finding the spot. The fix is a cut.
4. Where does the "mud" in most instruments usually sit?
- 20–40 Hz
- About 200–500 Hz
- 3–5 kHz
- 10–16 kHz
The low mids are where too many instruments overlap and build up mud.
5. What is a downside of linear phase EQ?
- It shifts phase near every band
- It can't boost
- Pre-ringing, extra latency and higher CPU use
- It only works on mono tracks
Linear phase keeps timing intact but adds latency and can smear transients with pre-ringing.
6. A vocal gets harsh only on its loudest notes. Which tool fits best?
- A static high shelf cut
- A high-pass filter
- A notch at 60 Hz
- A dynamic EQ band
A dynamic EQ only cuts when the harsh frequency crosses its threshold, leaving quieter notes untouched.