Multiband Compression

In-Depth Explanation

Multiband compression splits an audio signal into multiple frequency bands and compresses each band independently. A three-band compressor divides the signal into low, mid, and high frequencies. Each band gets its own threshold, ratio, attack, and release settings. This lets you control dynamics precisely without affecting the entire signal at once.

How Multiband Compression Works

A standard compression plugin processes the entire frequency spectrum together. If a kick drum triggers the compressor, the high frequencies duck along with the low frequencies. This can make a mix sound dull and lifeless every time the bass hits.

Multiband compression solves this by using crossover filters to split the signal. A three-band compressor uses two crossover points. Everything below the first crossover is the low band. Everything between the two crossovers is the mid band. Everything above the second crossover is the high band. Each band feeds its own compressor with independent settings.

You can compress the low band aggressively to control bass energy without touching the highs. You can compress the high band gently to tame harshness without affecting the low end. The bands are then recombined into a single output.

Common configurations:

• Three-band: Low, mid, high. The most common setup for mastering. Typical crossover points at 200 Hz and 2 kHz.
• Four-band: Low, low-mid, high-mid, high. More control for complex mixes. Typical crossovers at 120 Hz, 1 kHz, and 5 kHz.
• Five-band: Maximum control for problem mixes or broadcast processing. Used in broadcast limiters like the TC Electronic Finalizer.

Each band has the same parameters as a standard compressor: threshold, ratio, attack, release, and makeup gain. The difference is that each band only sees and affects its frequency range.

The crossover slopes matter. Steep slopes (24 or 48 dB per octave) create clean separation between bands. Gentle slopes (12 dB per octave) allow some overlap, which sounds more natural but provides less isolation. Most multiband compressors use 24 dB per octave slopes as a compromise.

Real-World Example

A mastering engineer receives a mix from an independent artist. The mix has two problems. The bass is inconsistent. Some sections hit 6 dB louder than others. The high end is harsh in the choruses where cymbals and synths pile up.

A single-band compressor cannot fix both problems. If the engineer compresses hard enough to control the bass, the high end gets dull every time the bass hits. If they compress gently to preserve the highs, the bass stays uncontrolled.

They insert a three-band compressor on the master bus with these settings:

Low band (20 to 200 Hz):

• Threshold: -20 dB
• Ratio: 3:1
• Attack: 15 ms
• Release: 150 ms
• Makeup gain: +2 dB

Mid band (200 Hz to 2 kHz):

• Threshold: -18 dB
• Ratio: 2:1
• Attack: 20 ms
• Release: 200 ms
• Makeup gain: +1 dB

High band (2 kHz to 20 kHz):

• Threshold: -22 dB
• Ratio: 2.5:1
• Attack: 5 ms
• Release: 80 ms
• Makeup gain: +1 dB

The low band compressor catches the inconsistent bass peaks and evens them out. The mid band stays mostly transparent. The high band compressor tames the harsh cymbal peaks in the choruses. The three bands recombine cleanly.

The result: the bass is now consistent within 2 dB across the entire track. The high end harshness is gone. The overall mix is 1.5 dB louder in LUFS without any additional limiting. The engineer used FabFilter Pro-MB, which costs $199. Free alternatives like TDR Nova offer similar multiband control for $0.

Why It Matters for Independent Artists

Multiband compression is a powerful tool for fixing problem mixes. It is also one of the easiest tools to misuse. When applied correctly, it solves issues that no single-band compressor can. When applied incorrectly, it destroys the balance of a mix.

Three situations where multiband compression helps independent artists:

• Mastering your own tracks: If your mix has an inconsistent low end or harsh highs, multiband compression on the master bus can fix it. Set conservative ratios (2:1 or 3:1) and low thresholds. The goal is transparent control, not obvious compression.
• Vocal processing: A multiband compressor on a vocal can tame sibilance in the high band while controlling bass resonance in the low band. This is more flexible than a dedicated de-esser, which only targets one frequency range.
• Taming resonant frequencies: If a mix has a resonant buildup at 400 Hz that jumps out in certain sections, a multiband compressor with a narrow mid band centered at 400 Hz can duck just that frequency when it gets too loud. This is dynamic EQ territory, and the line between the two tools is blurry.

A warning: multiband compression can introduce phase issues at the crossover points. The crossover filters shift the phase of frequencies near the split points. When the bands recombine, frequencies around the crossover can cancel or boost unexpectedly. High-quality multiband compressors use linear phase crossovers to avoid this, but linear phase mode adds latency. For real-time tracking, use minimum phase mode. For mastering, use linear phase.

The biggest mistake beginners make is over-compressing each band. If you set aggressive ratios on all three bands, you get a flat, lifeless, squashed mix. Start with gentle settings (2:1 ratio, low threshold) and increase only if you hear a specific problem. Read our mixing vs mastering guide and our mastering for streaming platforms guide for complete multiband settings.

Related Terms

• Compression - The foundational technique that multiband compression extends
• EQ (Equalization) - The frequency-splitting concept that multiband compression borrows
• Sidechain Compression - Another advanced compression routing technique
• LUFS - The loudness unit that measures the output of a multiband compressed master