The Compression Visualiser
See What Your Compressor Actually Does
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What Your Compressor Is Actually Doing
See the settings, understand the sound
The Signal Chain in Four Controls
Your audio comes in, the compressor watches its level, and the moment it crosses the threshold - the red dashed line above - the compressor turns it down. How much depends on the ratio. How fast it reacts is the attack. How fast it lets go is the release. Four controls, one job: reduce the level of audio that's too loud. The reason it gets confusing is that those four controls interact in ways that are hard to hear but easy to see. Lower the threshold to -20dB, push the ratio to 4:1, and watch the teal waveform pull away from the amber. That gap is gain reduction.
Attack Is the Control That Matters Most
Attack sets how quickly the compressor clamps down after the signal crosses the threshold. Set it to 0.5ms with Zoom on - the teal line catches the transient almost instantly. Now try 30ms and watch the transient spike through before compression kicks in. That spike is punch. Fast attack kills it, slow attack preserves it. This is the single biggest decision you make on drums - a snare that slaps versus a snare that thuds comes down to a few milliseconds of attack time.
Release Controls the Recovery
Watch the Gain Reduction graph below the waveform as you adjust release. The amber trace shows exactly how fast the compressor recovers. If the release is too slow, gain reduction builds up and doesn't reset before the next hit - that's pumping. If it's too fast on bass, you get harmonic distortion. The sweet spot is where the GR trace returns to near zero just before the next transient arrives.
Killing Transients
Toggle Zoom on and set the attack to 0.5ms. See how the compressed waveform meets the original almost immediately? The compressor is catching the initial snap before it reaches the listener. Slow the attack to 25ms and watch the transient punch through. If your drums sound lifeless after compression, your attack is almost certainly too fast. The Compression Troubleshooter walks you through diagnosing this in a real mix.
Pumping and Over-Compression
Set a low threshold (-25dB), moderate ratio (4:1), and a fast release (20ms). Watch the GR graph - the amber trace dips and snaps back aggressively on every transient. That rapid recovery is audible as a breathing, pumping effect. Now push the threshold to -30dB with a 10:1 ratio. The compressed waveform barely moves - the dynamics are gone. If the Peak GR meter shows more than 10dB, you're in aggressive territory. A healthy range is 3-6dB on individual tracks, 2-4dB on a bus, and 1-2dB on the mix bus.
Compression and the Bigger Picture
Corrective EQ before compression, tonal EQ after. The compressor reacts to whatever you feed it - remove problem frequencies first, compress a clean signal, then shape tone afterwards. The EQ Frequency Chart maps 21 instruments across the frequency spectrum to help you make that call.
Need starting-point settings for a specific instrument? The Compressor Calculator gives you research-backed recommendations for over 20 sources. Ask Dan anything about compression, EQ, or mixing - it's an AI tutor trained on 20 years of mixing experience. For the full collection, visit the Learning Hub.
Compression Glossary
Key terms from the visualiser above, explained for beginners.
- Threshold
The level at which the compressor starts working. Signal below the threshold passes through unchanged. Signal above it gets compressed by the amount set by the ratio. In the visualiser above, this is the red dashed line - everything above it gets processed, everything below is untouched.
- Ratio
How much the signal is reduced once it crosses the threshold. At 4:1, a signal 8dB over threshold is reduced to 2dB over. Higher ratios mean more aggressive compression. Above 10:1 approaches limiting. Ratios multiply in series - a 4:1 into a 3:1 creates an effective ratio of about 12:1.
- Attack Time
How quickly the compressor starts reducing gain after the signal crosses the threshold. Fast attack (under 5ms) catches transients and reduces punch. Slow attack (15-30ms) lets transients through, preserving snap and impact. In the visualiser, toggle Zoom on to see how attack time shapes the transient.
- Release Time
How quickly the compressor stops reducing gain after the signal drops below the threshold. Too fast on bass causes harmonic distortion. Too slow causes pumping as gain reduction builds up. The amber trace in the Gain Reduction graph shows exactly how fast the compressor is recovering.
- Makeup Gain
Volume added after compression to bring the overall level back up. Compression reduces peaks, which drops the average level. Makeup gain compensates. Critical for A/B comparison - always level-match before toggling bypass, because louder always sounds better to our ears regardless of whether the compression is actually helping.
- Gain Reduction (GR)
The amount the compressor is turning the signal down, measured in dB. Shown on the GR meter and as the amber trace in the Gain Reduction graph. A useful budget: 3-6dB on individual tracks, 2-4dB on a bus, 1-2dB on the mix bus. Gain reduction from multiple compression stages adds up cumulatively.
- Knee
Controls how gradually the compressor transitions from no compression to full compression at the threshold. A hard knee engages abruptly - the compressor is off, then on. Good for drums and aggressive compression. A soft knee eases in gradually over a few dB around the threshold - good for vocals and transparent levelling. Not shown in this simplified visualiser but present on all real compressors.
- Sidechain
The detection circuit that tells the compressor when to engage. By default it listens to the input signal, but you can filter it (high-pass at 80-150Hz to stop bass from driving excessive GR on buses) or feed it an external source (kick drum sidechaining a bass guitar so the bass ducks on every kick hit).
- RMS vs Peak Detection
Two ways a compressor measures the input signal. Peak detection responds to absolute waveform peaks - faster, catches transients. RMS detection responds to average energy over time - slower, more musical, closer to how we perceive loudness. Most modern compressors let you choose or blend between the two.
- Parallel Compression
Blending a heavily compressed copy of the signal with the uncompressed original. You get the energy and density of aggressive compression without losing the dynamics of the dry signal. Especially effective on drums. Set up via an aux send or a wet/dry mix knob on the compressor plugin.
- Program-Dependent Compression
A compressor mode where the attack and release times automatically adapt to the input signal. Opto compressors like the LA-2A are naturally program-dependent - the light element responds differently to different material. Simplifies setup but gives less precise control than setting attack and release manually.
- Limiting
Compression with a very high ratio, typically 10:1 or higher, often infinity:1. Prevents the signal from exceeding the threshold rather than gently reducing it. Used on the mix bus during mastering to control final output level and prevent clipping. In the visualiser above, push the ratio to 20:1 to see limiting behaviour - the compressed waveform essentially hits a ceiling.
Frequently Asked Questions
Common questions about audio compression, compressor settings, and how to use this tool.
What does a compressor do to audio?
A compressor reduces the volume of audio that exceeds a threshold you set. The amount of reduction is controlled by the ratio - at 4:1, a signal 8dB over the threshold becomes 2dB over. This evens out the dynamic range between the loudest and quietest parts, giving you a more consistent, controlled signal that sits better in a mix.
In the visualiser above, the amber waveform is the original signal and the teal waveform is the compressed result. The gap between them is the compression in action. Lower the threshold and increase the ratio to see more dramatic gain reduction.
Adjust the threshold and ratio sliders in the Compression Visualiser above to see this in real time.
What is gain reduction in compression?
Gain reduction (GR) is the amount in dB that the compressor is turning the signal down at any given moment. It fluctuates as the signal level changes - the compressor works harder on loud peaks and eases off during quieter moments.
A useful budget: 3-6dB on individual tracks, 2-4dB on bus compression, 1-2dB on the mix bus. More than 10dB on a single stage is heavy compression territory and should be a deliberate creative choice, not an accident.
The amber trace in the Gain Reduction graph below the waveform shows GR changing over time. The Peak Gain Reduction meter shows the maximum value.
What is the difference between threshold and ratio?
Threshold sets where compression begins. Ratio sets how hard it compresses. Think of threshold as the gate that decides what gets compressed, and ratio as the strength of the compression applied to whatever gets through that gate.
A low threshold (-30dB) with a gentle ratio (2:1) catches most of the signal but compresses it lightly - good for levelling. A high threshold (-6dB) with a heavy ratio (10:1) only catches the loudest peaks but squashes them hard - that's peak limiting. Both controls interact, so adjusting one usually means re-evaluating the other.
Try different combinations of threshold and ratio in the visualiser above and watch how the compressed waveform changes shape.
What does attack time do on a compressor?
Attack time controls how quickly the compressor clamps down after the signal crosses the threshold. A fast attack under 5ms catches the initial transient and squashes it - the drum hit or pick attack gets reduced before the listener hears it. A slow attack of 15-30ms lets that transient punch through before compression engages.
This is the single most impactful compression control on drums. It determines whether a snare snaps or thuds, whether a kick drum punches or pillows. If your drums sound lifeless after compression, your attack is almost certainly too fast.
Toggle Zoom on in the visualiser above and sweep the attack from 0.5ms to 30ms - watch the transient spike appear and disappear.
What does release time do on a compressor?
Release time controls how quickly the compressor stops reducing gain after the signal drops below the threshold. Too fast a release on bass or sustained sources causes harmonic distortion as the compressor rapidly cycles on and off. Too slow and gain reduction accumulates over successive hits, causing pumping.
The ideal release lets the compressor recover just before the next transient arrives. On a snare at 120 BPM, that means the GR needs to reset within about 500ms. On a fast hi-hat pattern, you need a much quicker recovery. Always match the release to the tempo and rhythm of the material.
Watch the Gain Reduction graph in the visualiser above as you adjust release - see how the amber trace recovers faster or slower.
How do I set attack and release on a compressor?
Start with medium values - attack around 10-15ms, release around 100-150ms - then adjust by ear and eye. For attack: slow it down until you hear the transient punch through, then stop. If you want more snap, go a bit slower. If you want more control, go faster. The sweet spot is where you get enough transient for impact without losing control of the peaks.
For release: watch the gain reduction meter and make sure it resets to near zero before the next hit arrives. If GR builds up over time, shorten the release. If the recovery sounds too abrupt or choppy, lengthen it. The Compressor Calculator gives you research-backed starting points for specific instruments.
Use the visualiser above to experiment with attack and release combinations and watch the waveform and GR graph respond in real time.
What compressor ratio should I use?
It depends on the source and the goal. Use 2:1 to 3:1 for gentle levelling - vocals, bass, mix bus. Use 4:1 to 6:1 for moderate control - drums, guitars. Use 8:1 to 10:1 for aggressive compression. Anything above 10:1 approaches limiting.
One thing most people don't realise: ratios multiply in series. A 4:1 compressor feeding into a 3:1 creates an effective ratio of about 12:1. So if you've got compression on the vocal, the vocal bus, and the mix bus, those ratios are stacking. Keep that in mind before cranking any single stage.
Drag the ratio slider in the visualiser above from 2:1 to 20:1 and watch the compressed waveform flatten against the threshold.
How do I set the threshold on a compressor?
Lower the threshold until the gain reduction meter starts moving on the loudest parts of the signal. For individual tracks, aim for 3-6dB of peak gain reduction. For bus compression, 2-4dB. For mix bus, 1-2dB.
Always set the threshold while listening to the loudest section of the song - usually the final chorus. If you set it during a quiet verse, you'll over-compress when the chorus hits. The threshold should catch the peaks without crushing the quieter moments.
Lower the threshold slider in the visualiser above and watch the red dashed line drop - everything above it gets compressed.
What does compressor ratio actually mean?
Ratio describes how much signal above the threshold is reduced. At 4:1, for every 4dB the signal exceeds the threshold, only 1dB comes through the other side. So 8dB over becomes 2dB over. 16dB over becomes 4dB over.
At 1:1 there's no compression at all - what goes in comes out unchanged. At infinity:1, no signal exceeds the threshold whatsoever - that's a brick wall limiter. Most mixing work happens between 2:1 and 8:1. The visualiser above makes this easy to see: push the ratio to 20:1 and watch the compressed waveform essentially hit a ceiling at the threshold line.
Try 2:1, 4:1, and 20:1 in the visualiser above to see the difference between gentle compression and limiting.
Why does my compressor kill the punch on drums?
Your attack time is too fast. Below about 10ms on most drums, the compressor catches the transient - the initial snap of the hit - before it reaches the listener. The drum still has body and sustain, but the impact is gone. It sounds flat and lifeless instead of punchy and exciting.
The fix is simple: slow the attack to 15-30ms. The transient punches through before compression engages, giving you snap and impact while still controlling the sustain. This is the most common compression mistake on drums, and the easiest to fix. The Compression Troubleshooter can walk you through a full diagnosis.
Toggle Zoom on in the visualiser above, set attack to 0.5ms, then try 25ms - watch the transient spike appear.
What is compression pumping and how do I fix it?
Pumping happens when the release time is too slow for the tempo of the material. The compressor doesn't recover between hits, so gain reduction accumulates - each successive hit drives it deeper. Then during a gap or breakdown, the compressor suddenly lets go and the volume surges up audibly. It sounds like the mix is breathing.
Fix it by shortening the release until the gain reduction resets before each new transient. Sometimes pumping is intentional - it's a classic effect on drum room mics and parallel compression. But on vocals, bass, or bus compression, it usually sounds wrong. The Compression Troubleshooter has a dedicated pumping diagnosis.
Watch the GR graph in the visualiser above - each hit should dip and return to near zero before the next hit arrives.
What is the difference between a compressor and a limiter?
A limiter is just a compressor with a very high ratio - typically 10:1 or higher, often infinity:1. Where a compressor gently reduces signal above the threshold, a limiter prevents it from exceeding the threshold at all. The signal hits a ceiling and goes no further.
Limiters are used on the mix bus during mastering to control final output level and prevent digital clipping. In practice, many compressor plugins become limiters when you push the ratio above 10:1. There's no hard boundary - it's a spectrum from gentle compression to brick wall limiting.
Push the ratio to 20:1 in the visualiser above and watch how the compressed waveform essentially flattens at the threshold - that's limiting in action.