What it is and how it works
An equalizer is a set of filters that raise or lower the level of a region of frequencies. Each band has three quantities: frequency (center or corner point, in Hz), gain (dB) and width (Q or bandwidth in octaves). A “bell” (peaking) EQ adds a band-pass-filtered copy to the signal, either positive (boost) or negative (cut); a shelf raises or lowers everything above or below a point; a filter (HP/LP) progressively removes whatever lies beyond the cutoff.
Almost all “normal” digital EQs are minimum phase (IIR): every change in amplitude also produces a small phase rotation around the frequency you touched. This is how analog EQs behave and it sounds natural; it becomes a problem only when you EQ two correlated signals differently (multiple microphones, layers, parallel bands). The variants (linear phase, dynamic, M/S, Pultec, graphic) are covered in the “EQ types” guide.
In the mix, EQ has four jobs: cleaning (rumble, mud, resonances), separating (making room between instruments that mask each other), balancing the tone (steering the sound toward its role) and coloring (emphasizing a character).
Q and bandwidth
Q = center frequency / bandwidth at −3 dB. Useful equivalents:
| Q | Width | Use |
|---|---|---|
| 0.5 | about 2.5 octaves | very wide color, soft “tilt” |
| 0.7 | about 2 octaves | presence, body, air |
| 1.4 | 1 octave | zone correction (mud, boxiness) |
| 2.9 | 1/2 octave | well-defined annoying zone |
| 4.3 | 1/3 octave | wide resonance, nasality |
| 8–20 | less than 1/6 octave | snare ring, whistles, 50 Hz hum and harmonics |
Some EQs (API, Neve, many plugins in “proportional Q” mode) narrow the Q as you increase the gain: a small boost is wide, a large one is narrower. In Fruity Parametric EQ 2 the width is set with the BW control, with Shift+drag on the point, or with the mouse wheel.
Parameters one by one
- Frequency: where the band acts. Move in octaves and half octaves, not a few Hz at a time: by ear the difference between 3.0 and 3.2 kHz is minimal, between 2 and 4 kHz it is enormous.
- Gain: corrective cuts 2–6 dB (up to 10–15 dB on narrow resonances), color boosts 1–3 dB, rarely beyond 4–5 dB. Beyond 6–8 dB of boost, the source sound is usually wrong.
- Q / BW: see the table. Rule of thumb: cut narrow, boost wide.
- Band type: peaking (bell), low/high shelf, high-pass/low-pass, band-pass, notch. Fruity Parametric EQ 2 has 7 bands and all of these types.
- Slope (only for filters and some shelves): 6, 12, 18, 24, 36, 48 dB/oct. In Fruity Parametric EQ 2 the filter slopes range from 12 to 48 dB/oct, in “Steep” or “Gentle” versions.
- Output / output gain: used to compare at equal volume. An EQ that raises the volume always seems “better”.
- Analyzer: Fruity Parametric EQ 2 shows a histogram or heatmap from 20 Hz to 20 kHz with a −60/−90/−120 dB range and a display slope (pivot, default 4.5 dB/oct) that makes a typical musical spectrum look “flat”. It is an aid, not a judge.
- Compare: in Fruity Parametric EQ 2 the Compare button stores a second setting for comparison (A/B).
Subtractive and additive EQ: the order of work
- High-pass on everything that shouldn't carry sub (see the table below). Slope 12–24 dB/oct. Raise the cutoff until you hear the sound thin out, then back off by about a third.
- Resonance cleanup with the sweep technique: narrow band (Q 6–10), +10/+12 dB boost, sweep until one spot “whistles” or booms more than the others, then turn it into a 3–8 dB cut. Don't make more than 3–4 narrow cuts per track: if you need more, the problem is upstream (microphone, room, preset).
- Wide zones: mud (200–400 Hz), boxiness (400–800 Hz), nasality (800 Hz–1.5 kHz), harshness (2–4 kHz). Cuts of 1.5–4 dB with Q 1–2.
- Color: wide boosts after compression (or before, if you want the compressor to react to that zone).
- Comparison at equal volume with the bypass, and always in the context of the mix, not in solo.
Masking and complementary EQ
Two sounds with energy in the same zone cover each other: the louder and denser one wins. The classic solution is complementary EQ: where the main instrument has its identity zone, the secondary one gets a 2–4 dB cut with the same Q. Examples: vocal with presence at 3 kHz → −2/−3 dB at 3 kHz on guitars and synths; kick with body at 60 Hz and bass at 100 Hz → −2 dB at 60 Hz on the bass and −2 dB at 100 Hz on the kick. If the conflict only occurs at certain moments, use a dynamic EQ with sidechain (see “EQ types” and “Sidechain”).
Frequency map (reference)
| Band | Hz | Feeling | Typical problem |
|---|---|---|---|
| Sub | 20–60 | pressure, physical weight | rumble, headroom consumption |
| Bass | 60–150 | body, kick punch, bass fundamental | bloat, buildup |
| Low mids | 150–400 | warmth, fullness | mud |
| Mids | 400 Hz–1.5 kHz | instrument presence, “wood” | boxiness, nasality, telephone sound |
| Upper mids | 1.5–4 kHz | attack, intelligibility | harshness, fatigue |
| Presence | 4–7 kHz | definition, consonants | sibilance (5–9 kHz) |
| Brilliance | 7–12 kHz | shine, cymbals | digital harshness |
| Air | 12–20 kHz | space, openness | breath, hiss |
Starting high-pass by instrument
| Instrument | Suggested high-pass |
|---|---|
| Kick | 20–30 Hz (cleanup only), never above the fundamental (40–60 Hz) |
| 808 / sub | 20–25 Hz |
| Electric bass | 30–40 Hz |
| Snare | 60–100 Hz |
| Hi-hat, cymbals | 200–500 Hz (overheads 80–150 Hz if they carry the drums) |
| Male vocal | 70–100 Hz |
| Female vocal | 100–150 Hz |
| Backing vocals | 150–250 Hz |
| Acoustic guitar | 80–120 Hz |
| Distorted electric guitar | 70–100 Hz (+ LP 8–12 kHz) |
| Piano (full mix) | 40–80 Hz |
| Pads, synth strings | 100–250 Hz |
| Leads and plucks | 150–300 Hz |
| Reverb returns | 150–400 Hz (+ LP 6–10 kHz) |
Starting settings by instrument
- Kick: HP 25 Hz; boost 50–70 Hz +2 dB Q 1 (weight); cut 250–400 Hz −3 dB Q 1.5 (cardboard); boost 3–5 kHz +2 dB Q 1 (beater click).
- 808: HP 25 Hz; control 100–200 Hz (−2 dB if it clashes with the kick); saturation instead of boosting to make it audible on phones.
- Snare: HP 80 Hz; 180–250 Hz +2 dB (body); find the 400 Hz–1 kHz ring with a sweep (−4/−8 dB, Q 8); 5–8 kHz +2 dB (snare wires).
- Vocal: HP 80–120 Hz; 200–350 Hz −2/−3 dB (mud, proximity effect); 800 Hz–1.2 kHz −1/−2 dB if nasal; 3–5 kHz +1/+3 dB (presence); shelf 10–12 kHz +2 dB (air) after the de-esser.
- Distorted guitars: HP 80 Hz, LP 10–12 kHz; 300–500 Hz −2 dB; 2–4 kHz watch the harshness; sweep for the 6–8 kHz “fizz”.
- Piano/Rhodes: 200–300 Hz −2 dB in a full mix; 2–3 kHz +1 dB for the attack.
- Pad: HP 150–250 Hz; wide cuts at 1–3 kHz to leave room for the vocal.
By genre
- Trap/drill: low end dominated by the 808; everything else with a generous HP (melodies and pads above 150–250 Hz); rap vocal with marked 3–5 kHz presence.
- Pop/K-pop: vocal well forward (2–5 kHz) and air at 10–16 kHz; bright mix, tight control of 200–400 Hz.
- Rock/metal: guitars occupying 100 Hz–5 kHz; HP and LP on guitars to leave sub and air to kick, bass and cymbals; cuts at 2–4 kHz if they fatigue.
- Jazz/acoustic/orchestral: minimal, wide EQ; microphone technique and arrangement are preferred.
- House/techno: kick and bass carefully separated below 120 Hz; upper mids controlled for loud club listening.
Common mistakes
- EQing in solo: the “perfect” sound on its own is often too full in the mix.
- Boosts that raise the volume and fool you: compensate with the output gain.
- Lots of small boosts in the same zone (3 kHz on vocal, guitars, synths, cymbals): buildup and an aggressive mix.
- High-passes that are too high on every track: the mix loses warmth (phase summing and absence of 100–250 Hz).
- Trusting only the analyzer: a peak in the spectrum is not always a problem (the bass fundamental has to be there).
- Using EQ to fix a wrong sound: if you need more than 8 dB of correction, change the sample, preset or microphone technique.
How to hear it
- Slow sweep with a narrow band at +10 dB: you learn where each sensation lives (rumble, mud, boxiness, nasality, harshness, sibilance, air).
- A/B with bypass at equal volume; listen at low volume (the ear is more honest in the midrange) and in mono.
- Exercise: on a reference track use a wide band-pass and listen one octave at a time; then do the same on your own mix.
Starting settings
| Parameter | Value | Why |
|---|---|---|
| Q for corrective cuts | 4–10 (resonances), 1–2 (zones) | Hits the flaw without hollowing out the sound. |
| Q for coloring | 0.5–1.2 | Wide curves sound natural and musical. |
| Typical cut | 2–6 dB (up to 10–15 dB on narrow resonances) | Beyond 6–8 dB on wide zones it is better to change the source. |
| Typical boost | 1–3 dB | Large boosts increase harshness, clipping and masking. |
| High-pass slope | 12–24 dB/oct (48 dB/oct only for surgical cuts) | Compromise between cleanup and phase rotation near the cutoff. |
| Search sweep | +10/+12 dB, Q 6–10 | Makes the resonance to cut obvious. |
| Output gain | Compensates for the perceived gain | Honest comparison at equal volume. |
| Position | Corrective before compression, color after | The compressor doesn't react to what you would remove anyway. |
Frequencies to watch
| Range | What to do |
|---|---|
| 20–40 Hz | Cleanup with HP on almost everything except kick, 808 and bass: frees up headroom without changing the tone. |
| 60–120 Hz | Kick and bass weight: decide which of the two has the lower peak and separate them with complementary EQ. |
| 200–400 Hz | Cumulative mud: small cuts (1–3 dB) on many tracks are worth more than one big cut on the bus. |
| 400–800 Hz | Boxy or cardboard sound on kick, toms, vocal, acoustic guitar: cut with Q 1.5–3. |
| 2–5 kHz | Maximum ear sensitivity (equal-loudness curves): 1–2 dB moves change the perception a lot. |
| 5–9 kHz | Sibilance and fizz: de-esser or dynamic EQ first, then static EQ if needed. |
| 10–16 kHz | Air: soft shelf or wide bell Q 0.5–0.7; better with character EQs (Pultec, Baxandall). |
Example chain
| Step | Tool | Settings | Why |
|---|---|---|---|
| Cleanup / filters | Fruity Parametric EQ 2 / FabFilter Pro-Q 3-4 / TDR Nova | HP per the table, 12–24 dB/oct; resonance notches Q 6–10 | Removes what isn't needed before any dynamics processing. |
| Dynamics control | Fruity Compressor / Fruity Limiter (COMP) / Pro-C 2 | Ratio 2–4:1, GR 3–6 dB | Stabilizes the level: the EQ after it works on a consistent signal. |
| De-esser or dynamic EQ | Maximus (high band) / Pro-DS / Pro-Q in dynamic mode | 5–9 kHz, −3/−6 dB on peaks only | Controls sibilance and harshness that appear intermittently. |
| Color EQ | Fruity Parametric EQ 2 / Pultec (UAD, Waves PuigTec, IK) / Baxandall | Shelf +1/+3 dB, wide bells Q 0.7 | Gives the final character once the dynamics are under control. |
| Saturation (optional) | Fruity Blood Overdrive / Soundgoodizer / Decapitator | Light drive, mix 20–50% | Harmonics change the tonal perception: recheck the EQ afterward. |
| Sends | Fruity Reeverb 2 / LuxeVerb / Fruity Delay 3 on separate mixer tracks | EQ on the return: HP 150–400 Hz, LP 6–10 kHz | Effects should be EQed like instruments. |
How to check the result
- Spectrum before/after: a good subtractive EQ reduces narrow peaks without lowering the band average by more than 2–3 dB.
- No 1/3-octave band sticking out by more than 6 dB from its neighbors in the track's average spectrum (resonance).
- Mix: the average spectral curve falls gradually from bass to treble, with a slope similar to the genre's references (with the analyzer tilted by 4.5 dB/oct it looks roughly flat).
- Track loudness unchanged within 0.5 LU between EQ on and bypass when you judge the tone (output compensated).
- No energy below 40 Hz on any non-bass track (check with the analyzer on the solo track).
- Correlation unchanged after the EQ (a normal EQ on a stereo signal must not change the phase between channels).