The Frequency
Spectrum, Mapped
Every EQ move, every compression choice, every panning call is a decision about frequency real estate. This covers what lives where in the spectrum, why subs need to be mono, how to carve space for competing elements, and the problem zones worth knowing by ear.
How equal loudness curves affect your mix decisions
Your ear peaks in sensitivity around 3–4 kHz, so a boost there hits harder than the same boost at 200 Hz. At low volumes, bass and treble drop below your perceptual threshold, so a mix that sounds balanced loud can feel thin and harsh when you turn it down, and the low end seems to jump when you push the volume back up.
The map: all seven bands, interactive
The bar is logarithmically scaled. Click any band to see what lives there, the right stereo approach, and the EQ moves worth knowing.
Sub Bass
Everything below 60 Hz. You feel this more than you hear it — the physical pressure of a club system. Should be 100% mono. Most consumer speakers and earbuds reproduce very little content below 80 Hz, so information here needs to be powerful but controlled.
Sum to mono. Phase cancellation is catastrophic at these frequencies.
- ■Kick drum fundamental (40–60 Hz)
- ■Bass synth / 808 root note (40–80 Hz)
- ■Sub oscillator in bass patches
- ■Room resonance and pressure
- →High-pass everything that doesn't need sub energy here
- →Low-cut at 20 Hz to remove infra-sub rumble
- →Keep mono — sum to mono with a low shelf M/S cut on the S channel
- →Gentle low-shelf boost (≤2 dB) for weight if needed; avoid narrow peaks
- !Flabby, undefined low end from room resonance (20–40 Hz)
- !Phase cancellation when stereo subs collapse to mono
- !Over-boosting causes speaker overexcursion and limiter pumping at mastering
- !Kick and bass fighting for the same 50–60 Hz fundamental
Bar widths are logarithmic (octave-proportional). Click any band to explore its content, EQ moves, and stereo rules.
One element per range
| Element | Primary frequency ownership |
|---|---|
| 808 / sub bass | 30–80 Hz sub fundamental — nothing else here |
| Kick drum | 60–120 Hz body, 2–4 kHz click/attack |
| Bass synth | 80–300 Hz fundamental and low harmonics |
| Synth pads | 200 Hz–1 kHz warmth; high-passed below 100 Hz |
| Lead synth | 500 Hz–4 kHz — the intelligibility and character range |
| Vocals | 200 Hz–8 kHz — broadest range, needs careful carving |
| Hi-hats / cymbals | 5–16 kHz — no reason for content below 200 Hz |
| Clap / snare | 200 Hz body + 2–5 kHz attack — a wide range owner |
Sub bass must be mono
Sub below 80 Hz needs to be mono. Verify it with a correlation meter, not just by ear. Club systems run a single sub array or multiple subs fed the same mono signal, so phase differences in that range don't attenuate: they cancel. Phones and Bluetooth speakers do the same thing. The ear can't localize anything below ~200 Hz anyway, so stereo sub isn't really adding width, so it's just introducing phase problems with no perceptual benefit.
The fix: M/S EQ
In Pro-Q 3: add a band, set it to Side-only, high-cut at 80 Hz. In Ableton EQ Eight: M/S mode, high-pass on the Side channel at 80 Hz. Done.
M/S EQ approach for sub — standard mastering technique: Low shelf @ 80 Hz: +0 dB (M), −∞ dB (S) → forces sub to 100% mono Low shelf @ 120 Hz: +0 dB (M), −6 dB (S) → gentle low-end stereo reduction Above 120 Hz: M and S equal → full stereo preserved above crossover Implementation in FabFilter Pro-Q 3: 1. Set processing mode to "Mid/Side" 2. Band 1: Low Cut, Side channel only, 80 Hz, 24 dB/oct → kills all sub stereo 3. Band 2: Low Shelf, Side channel only, 120 Hz, −6 dB → reduces bass stereo 3. Bands 3+: Left/Right or Stereo mode — normal mixing Implementation in Ableton EQ Eight: 1. Click "M/S" button at top 2. Switch to S (Side) channel using the M/S toggle in EQ Eight 3. Apply a high-pass filter at 80 Hz to the S channel — removes all stereo sub content 4. Optional: apply a low shelf at 120 Hz to the S channel, −4 to −6 dB
Masking and frequency relationships
The kick/bass problem at 60–120 Hz
Masking is a separation problem, not a level problem. Kick and bass both sit in 60–120 Hz, so when the kick hits, its transient masks the bass, and the sustained bass makes the kick sound dull. Turning either one up makes it worse. There are two approaches that actually help:
EQ carve approach (static):
Bass synth:
- Narrow cut at 70–80 Hz (where kick lives)
- Gentle boost at 100–150 Hz (bass owns this)
- High-pass at 30 Hz (remove infra-sub)
Kick drum:
- Narrow cut at 100–120 Hz (where bass lives)
- Gentle boost at 60–70 Hz (kick fundamental)
- High-pass at 40 Hz (tighten sub)
Now both elements exist simultaneously
without cancellation or masking.Mid-range mud at 200–400 Hz
Bass harmonics, synth pads, vocal chest tone, and snare body all pile up at 200–400 Hz. Fix it with systematic high-passing: pads at 120–200 Hz, leads at 150–250 Hz, atmospherics at 200–300 Hz. Each cut is tiny in isolation. Stacked across 8–12 elements, the midrange opens up.
Stereo width by frequency
Mid/Side (M/S) processing
M/S splits your stereo signal into Mid (identical in both channels) and Side (the difference). EQ or compress each independently. You can target stereo content at specific frequencies without touching the mono center, but L/R mode can't do this.
| Frequency Range | Stereo Recommendation |
|---|---|
| 20–80 Hz (Sub) | Mono — kill all Side content below 80 Hz |
| 80–200 Hz (Low Bass) | Narrow stereo only — Side channel −6 to −12 dB |
| 200–500 Hz (Low-Mid) | Narrow — keep width controlled; cut Side for mud |
| 500 Hz–2 kHz (Mid) | Medium — moderate width is fine and natural here |
| 2–5 kHz (Upper Mid) | Medium-wide — stereo movement adds presence |
| 5–10 kHz (Presence) | Wide — full stereo works safely in this range |
| 10–20 kHz (Air) | Wide — shimmer and air are where stereo imagery lives |
Problem frequencies: eight zones to know
Infra-sub rumble
Felt, not heard. Makes woofer cones move without audible pitch. Triggers limiters at mastering without the listener noticing anything.
Spectrum analyzer. Content below 30 Hz with no musical reason to be there.
HP at 20–30 Hz on every channel. Most speakers roll off below 30 Hz, so this energy is wasted headroom.
Mud — boxy, boomy, cardboard
Warm and thick but nothing is clear. Kick sounds dull, bass undefined, leads distant.
Sweep a narrow boost (4–6 dB, Q = 3.0) through 200–400 Hz on the master. The problem frequency jumps out as a recognizable resonance.
HP non-bass elements. Narrow cut on the worst offender. M/S Side cut in this range. Untreated rooms also build up here.
Honk — nasal, telephone, hollow
Nasal, megaphone-like. Usually from a specific instrument or resonant synth patch.
Narrow-sweep boost through 700 Hz–1.2 kHz. The honk frequency makes the source instantly objectionable.
Narrow cut (Q = 2–4), typically 2–4 dB, applied to the source. Multiple sources get slightly different notches.
Harshness — aggressive, fatiguing, teeth-on-edge
Feels exciting at first, causes ear fatigue within minutes. Distorted synths, crunchy bass, overdriven leads.
The ear's most sensitive range (Fletcher-Munson peak). Boosts here feel larger than they measure. Check at low volume: harsh content here is still unpleasant when quiet.
High-shelf roll-off on drum bus from 3 kHz, −1–2 dB. Notch the specific resonance on the offending source. Saturation instead of hard distortion keeps this range cleaner.
Sibilance — spikey, ssss, de-essing territory
Excessive S and SH sounds in vocals. Metallic spikiness in hi-hats and cymbals.
Spectrum analyzer or de-esser. Peak usually falls between 5–8 kHz depending on the voice.
De-esser (iZotope RX, FabFilter Pro-DS, built-in Logic/Ableton) or dynamic EQ. Don't reach for a broadband high-shelf cut, because you'll lose presence and air across the whole mix.
Brittle highs — glass, digital harshness
Glassy, thin, over-bright. Digital synths that don't anti-alias, heavily processed samples, or an over-boosted master shelf.
A/B against a reference. If your high end sounds harder, you're over-represented at 10–12 kHz.
High-shelf cut at 10 kHz, −1–2 dB. Analog-style saturation softens digital transient spikes. Check inter-sample peaks: content here can clip between samples when the meter reads clean.
Excessive air — ear fatigue from overdone shimmer
Mix feels open at first, tiring after a few minutes. Usually over-applied air EQ.
Cut everything above 16 kHz. If the mix feels more relaxed immediately, you had too much up there.
Gentle high-shelf cut at 16–18 kHz, −1–2 dB. Streaming encoders (AAC 256 kbps, MP3 320 kbps) roll off above 15–16 kHz, so air you added above that point won't survive the encode.
Practical EQ principles
1. High-pass everything that doesn't need low end
| Element | Recommended high-pass point |
|---|---|
| Kick drum | 30–40 Hz — remove infra-sub, keep low body |
| Snare drum | 100–120 Hz — no fundamental below this |
| Bass guitar / synth bass | 20–30 Hz — control, don't restrict |
| Synth lead | 100–200 Hz — depends on how low the patch plays |
| Synth pad | 100–200 Hz — pads rarely need sub energy |
| Vocal | 100–120 Hz — removes mic proximity and room buildup |
| Piano (mid-high role) | 150–250 Hz — if piano is not the bass element |
| Hi-hats / cymbals | 300–500 Hz — nothing useful below here |
| Strings / FX layers | 200–400 Hz — depends on role in the mix |
| Atmospheric textures | 200–500 Hz — nothing below this adds anything |
2. Cut narrow, boost wide
Problems are narrow: a resonant peak at 320 Hz, a harsh overtone at 3.2 kHz. Tight Q (2.0–6.0), hit the problem without wrecking the surrounding frequencies. Boosts add character (warmth, air, presence), and character is broad. Wide boost (Q = 0.5–1.5) sounds natural. Narrow boost sounds like a resonance you put there on purpose.
3. Cut before you boost
4. Reference constantly
Your ears adapt to your mix within minutes. Import a released track from the same genre, LUFS-match it, and A/B. Focus on sub vs. kick vs. midrange balance, brightness at 5–10 kHz, and perceived width. Problems you've been sitting with for hours show up in thirty seconds.
Frequency band quick-reference
Sub Bass · 20–60 Hz
808 / sub fundamental, kick sub-harmonics
Mono — kill Side channel below 80 Hz
HP at 20 Hz; gentle low-shelf only; M/S kill S channel
Phase cancel in mono; vinyl lathe; club sub system
Bass · 60–250 Hz
Kick body, bass fundamental, 808 tail
Narrow stereo — minimal Side content
Sidechain bass to kick; EQ carve at 80–120 Hz
Kick/bass masking; 200 Hz mud buildup; over-compression
Low-Mid · 250–500 Hz
Bass harmonics, snare body, vocal chest
Narrow — M/S Side cut reduces mud
HP non-bass at 100–200 Hz; narrow cut at 300–400 Hz
Mud accumulation — most common dense-mix problem
Mid · 500 Hz–2 kHz
Vocal intelligibility, snare crack, lead body
Medium — protect this range
Narrow cut at 800 Hz–1 kHz for honk; broad boost for phone translation
Masking between vocal and lead; hollow mixes from over-cutting
Upper Mid · 2–5 kHz
Vocal articulation, snare attack, synth overtones
Medium-wide
Handle with extreme care — ear peaks at 3–4 kHz; notch harsh resonances
Listener fatigue — any boost here fatigues faster than any other range
Presence · 5–10 kHz
Hi-hat body, vocal sibilance, cymbal character
Wide — safe for stereo here
De-ess at 5–8 kHz; high-shelf for brightness; cut brittle hi-hats
Sibilance; spikey digital hi-hats; headphone vs. speaker translation
Air · 10–20 kHz
Cymbal shimmer, vinyl texture, reverb tails
Wide
Gentle high-shelf +1–2 dB at 12–16 kHz; HP at 18 kHz to remove noise
Ear fatigue from over-boosting; streaming codec rolloff above 16 kHz
Three universal rules
Kill the Side channel below 80 Hz on the master. Verify in mono before every export. Club systems, phones, and Bluetooth speakers all hear your sub collapsed.
Problem frequencies are narrow resonances: use a surgical Q. Character boosts are broad shelves or wide bells: use a musical Q. Never boost narrow.
This is where the equal loudness curves are flattest and your ear is most reliable. Calibrate once with an SPL meter. Work there consistently.