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Module Compressor Calculator
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// Free Tool — Compression

Compressor Calculator

Pick what you're compressing and what you're going for. Get starting points for attack, release, ratio, threshold, and compressor type — with the reasoning behind every number.

Find Your Starting Point

Starting Point
Kick → Punch
Compressor Type

These topologies suit this goal. If you have one, use it. If not, the settings below approximate the behaviour on any compressor.

Settings (for any compressor)

Set the threshold until gain reduction sits within the suggested range. Match output level to input (bypass should be the same loudness).

Why This Works

What to Listen For

If It Sounds Wrong

These are starting points, not answers. The numbers get you in the ballpark — your ears take you the rest of the way. If you treat these as presets and never adjust them, you've missed the point. Trust your ears. If something sounds good, it is good.

// How It Works

How the Compression Calculator Works

Choose what you’re compressing, then select your goal. The compression calculator gives you two paths depending on your setup:

If you have a specific compressor type – opto, FET, VCA, Vari-Mu – the topology recommendations tell you which suits the goal. These compressors have their own built-in character and often their own timing behaviour. An LA-2A doesn’t have attack and release knobs because the circuit handles that automatically. An 1176 has fixed timing options rather than free-range millisecond values. When using these, you’re leaning on the compressor’s inherent sound – just set your threshold and ratio and let the character do the work.

If you’re using a stock plugin or generic compressor with full control over attack, release, ratio, and threshold – that’s what the settings are for. These numbers approximate the behaviour of the recommended topology on a compressor that doesn’t have that built-in character.

So it’s not “use these settings on an LA-2A.” It’s “use an LA-2A if you have one, or dial in these settings on a stock compressor to get in a similar ballpark.”

The recommendations come from real-world mixing practice. They’re starting points that get you moving quickly so you can spend more time listening and less time guessing.

Want to see what these settings actually do? The Compression Visualiser lets you watch compression shape the signal in real time.

Built by Dan Murtagh – Melbourne-based mix engineer and audio educator at Collarts.

// FAQ

Compression FAQ

What ratio should I use for vocal compression?
For transparent levelling, use 2:1 to 4:1 with 2-4dB of gain reduction. For more presence and punch, 4:1 to 6:1 with a slower attack (10-25ms) to let consonants through. The ratio matters less than the attack time and gain reduction - a gentle ratio with too much gain reduction still sounds over-compressed.
What attack and release times should I use for drums?
For punch (transient emphasis), set attack to 15-30ms to let the beater or stick hit through, with a fast release (30-80ms) so the compressor resets before the next hit. For sustain (fuller body), use a faster attack (1-10ms) and slower release (100-200ms). The attack time is the most important control on drums - it determines whether you emphasise the hit or the body.
How much gain reduction should I aim for?
As a guideline: individual tracks 3-6dB, drum bus 2-4dB, mix bus 1-2dB. But gain reduction is cumulative across stages. A track compressed 4dB on the insert, plus 3dB on the bus, plus 2dB on the mix bus has far more total compression than any single meter suggests. Think of gain reduction as a budget - every dB you spend at one stage is a dB you cannot spend elsewhere.
How do I compress bass guitar?
For consistent level, use an opto compressor at 3:1-4:1 with 3-6dB of gain reduction and a release above 100ms. For more defined note attacks, use a FET or VCA with a slower attack (10-25ms) to let the pluck through. Keep the release above 100ms on bass - if it is too fast, the compressor tracks individual wave cycles and creates harmonic distortion.
What are good mix bus compression settings?
Start with a VCA bus compressor (SSL G-Bus style) at 2:1-3:1 ratio, 10-30ms attack, 100-300ms release, and just 1-2dB of gain reduction. The goal is cohesion, not control. The mix should feel more finished and unified without losing energy or dynamics. If it sounds squashed, reduce gain reduction first.
Should I compress acoustic guitar?
Usually yes, because the dynamic range between a soft fingerpick and a hard strum can be large. For smooth levelling, use 2:1-4:1 with 2-4dB of gain reduction and an opto compressor. For more presence, use a VCA or FET with a slower attack (15-30ms) to let the pick transient through. Keep gain reduction gentle - acoustic guitar sounds over-processed quickly.
What's the difference between opto, VCA, FET, and vari-mu compressors?
Opto (LA-2A style) is smooth and slow with automatic timing - best for transparent levelling. VCA (SSL G-Bus, dbx 160) is fast, precise, and clean - best for bus compression and transparent control. FET (1176 style) is fast and aggressive, adding harmonic brightness - best for punch and character. Vari-Mu (Fairchild style) is tube-based, warm, and gentle - best for mix bus glue and vintage colour.
What is the best compressor plugin for vocals?
It depends on the goal. For smooth, invisible levelling, an LA-2A-style opto compressor (CLA-2A, Tube-Tech CL1B). For presence and forward energy, an 1176-style FET (CLA-76, Purple MC77). A common professional approach is both in series: FET first for 2-3dB of peak control, then opto for 2-3dB of gentle levelling. Each stage doing less work sounds more natural than one compressor doing everything.
Should I compress before or after EQ?
Corrective EQ before compression, tonal EQ after. If there is a problem frequency (mud, resonance, boxiness), cut it before the signal hits the compressor. The compressor reacts to whatever you feed it - a 300Hz resonance spike will cause the compressor to trigger on that spike and duck the whole signal. Fix the EQ problem first, then compress a clean signal. Tonal boosts (presence, air) work better after compression.
What is glue compression?
Glue compression is light bus compression that makes multiple tracks feel like they belong together. When several tracks share the same compressor, they rise and fall as a unit rather than independently. A drum bus with 2-4dB of glue makes the kick, snare, and cymbals respond together. On the mix bus, 1-2dB creates the cohesive finished record quality. VCA bus compressors are the classic choice.
How do I know if I'm over-compressing?
The mix will sound flat, lifeless, or fatiguing. Bypass all compressors and listen to the raw mix - it should sound dynamic and alive even if it is messy. Add compressors back one stage at a time. When the mix starts to flatten, that stage needs to be backed off. Also: always level-match before comparing compressed to uncompressed. Louder always sounds better, so without matching levels you cannot judge what the compression is actually doing.
// Go deeper

The Compression Code

This calculator gives you the numbers. The course teaches you to hear why they work — a framework for making compression decisions by ear, the way I teach it at university.

See the Course