Used well, multiband compression mastering is one of the most surgical tools you have: it lets you tame a boomy low end or a harsh upper midrange without touching the frequencies that are already sitting perfectly. Used badly, it flattens the life out of a track and introduces pumping you cannot un-hear. The difference is entirely in restraint and in understanding what problem you are actually solving. This guide walks through when to reach for a multiband compressor on the master bus, how to set crossovers and ratios, and the real gain-reduction amounts that keep a master transparent.
When multiband compression earns its place
A single full-band compressor reacts to whatever is loudest across the entire spectrum. So when a kick drum hits, it ducks your vocals and cymbals too. Multiband compression splits the signal into frequency bands and compresses each independently, which lets you fix one part of the spectrum in isolation. On a master, that is useful for specific, diagnosable problems, not as a default:
- A low end that pumps or booms on the loudest notes, where the bass and kick swell inconsistently. Compress just the lows and the top stays open.
- A harsh or fatiguing upper-midrange around 2-5 kHz that only spikes on certain vocal notes or cymbal crashes. A dynamic touch there beats a static EQ cut.
- Inconsistent overall balance between sections, where the low mids get thick in the chorus. Gentle control of that band evens it out.
If none of those describe your mix, you probably do not need multiband on the master at all. The single best habit in mastering is to only add a process when you can name the problem it fixes.
Setting crossovers, ratios and thresholds
Most mastering multiband compressors default to three or four bands. Sensible starting crossover points for a typical full-range mix:
- Low band: below roughly 120 Hz, covering sub and bass.
- Low-mid band: about 120 Hz to 800 Hz, the body and warmth region.
- High-mid band: about 800 Hz to 5 kHz, where vocals, snare and presence live.
- High band: above 5 kHz, cymbals and air.
Now the amounts, which are the whole point. On a master you want each band doing very little:
- Ratio: keep it gentle, around 1.5:1 to 2:1. Mastering is not the place for 4:1 or higher on the bus.
- Gain reduction: aim for only 1 to 3 dB on any band, and only on the passages that actually cause the problem. If a band is compressing 6 dB continuously, you have an EQ problem, not a dynamics one, so fix it with EQ instead.
- Attack: for the low band, a slower attack (30-50 ms) lets the kick transient punch through before compression clamps the sustain. For the high band, a faster attack (5-15 ms) catches harsh transients. Why? Because slow attack preserves punch, fast attack tames spikes.
- Release: time it to the tempo so the compressor recovers between hits and does not pump. Auto-release modes on quality plugins handle this well.
- Threshold: set it so the meter only lights up on the loudest, most problematic moments, not constantly.
Reach for a transparent, well-metered multiband for this. FabFilter Pro-MB is a strong choice because it shows real-time gain reduction per band and lets you set custom crossover slopes, and its dynamic-EQ-style behaviour is very transparent. The multiband module inside iZotope Ozone is another common option and integrates with the rest of its chain.
Multiband compression versus dynamic EQ
For a lot of mastering problems, a dynamic EQ is actually the gentler, more precise tool. Multiband compression splits the signal at crossover points, which can introduce phase interaction at the crossovers. A dynamic EQ instead applies a bell curve that only engages when a frequency exceeds a threshold, so it is more localised and phase-friendly.
- Use multiband compression when you want to control the overall dynamics of a broad frequency region, for example glue and control across the whole low end.
- Use dynamic EQ when the problem is a narrow, occasional resonance, for example a single harsh vocal note around 3 kHz or a boomy 80 Hz that only spikes on certain bass notes.
Many plugins blur the line, but the mental model helps you pick the least invasive fix.
Common multiband mistakes to avoid
Most bad multiband mastering comes from a handful of repeatable errors. Watch for these:
- Compressing every band because you can. If a band’s dynamics are fine, leave it alone. Idle bands should show zero gain reduction.
- Using it as a tone control. If you want a band permanently quieter or louder, that is an EQ job. Multiband compression is for controlling how a band moves over time, not for a static level change.
- Fast attack on the low band. Clamp the sub too quickly and you kill the kick’s punch, leaving a lifeless thud. Let the transient through, then control the sustain.
- Ignoring the crossover phase. Steep crossovers can smear transients. On transparent plugins, a gentler crossover slope often sounds more natural on a full mix.
- Not gain-matching the bypass. Compression lowers level, so an uncompensated comparison always flatters the processed version. Match output level before you judge.
Checking your work and staying subtle
Always A/B against the bypassed signal at matched loudness. Because compression changes level, an uncompensated bypass makes the compressed version sound “better” just because it is louder. Use the plugin’s gain-match feature or trim the output so both are the same perceived volume, then decide honestly whether the multiband is helping. Meter the final result with a loudness meter and keep your master landing around -14 to -10 LUFS integrated with a true-peak ceiling of -1 dBTP, remembering that multiband compression is a corrective step, not your loudness stage; the limiter handles level last.
For where multiband sits in the wider signal chain, our mixing and mastering guide lays out processor order, and the free spectrum and loudness utilities in our audio tools hub help you spot which band actually needs attention before you touch a control. Treat multiband compression mastering as a scalpel: a decibel or two on the one band that has a real problem will do more for your master than heavy-handed compression across the whole spectrum ever could.
