1Understanding Compression
Dynamic range compression reduces the volume difference between loud and quiet parts of audio. It automatically turns down signals that exceed a threshold, creating more consistent levels and allowing overall loudness increases without clipping.
Compression is arguably the most important tool in modern mixing and mastering. It shapes transients, controls dynamics, adds punch and sustain, glues tracks together, and enables the loud, present sound that defines contemporary production.
Our compression calculator helps you understand the mathematics behind compression settings. By visualizing how threshold, ratio, and makeup gain interact, you'll develop intuition for setting compressors effectively in your DAW.
2Key Parameters
Threshold determines when compression begins. Signals below the threshold pass unchanged; signals above get compressed. Lower thresholds mean more signal gets processed; higher thresholds affect only the loudest peaks.
Ratio controls compression intensity. At 4:1, for every 4dB above threshold, only 1dB passes through. Higher ratios create more aggressive compression; ratios above 10:1 approach limiting where virtually no signal exceeds the threshold.
Attack and release (not modeled in this calculator) control compression timing. Fast attacks catch transients; slow attacks let them through. Release determines how quickly compression stops after signal drops below threshold.
The Compression Formula: Gain Reduction = (Signal above threshold) × (1 - 1/Ratio). This simple formula governs all compression behavior and helps predict results from any setting combination.
3Threshold Deep Dive
Threshold is measured in dBFS (decibels relative to full scale) in digital systems. 0 dBFS is the maximum possible level; thresholds are negative values below this ceiling. A threshold of -20 dBFS means compression begins when signals exceed -20 dBFS.
Setting threshold requires considering your source material. Vocals with wide dynamic range might need thresholds catching most of the signal. Drums might only need peak control with higher thresholds targeting transients only.
Watch your gain reduction meter while setting threshold. Consistent gain reduction throughout a passage indicates the threshold is set appropriately. Reduction only on peaks suggests you're catching just the loudest moments.
4Ratio Explained
Ratio describes input-to-output relationship above threshold. At 2:1, 10dB above threshold becomes 5dB above—the difference is halved. At 4:1, that 10dB becomes 2.5dB. At 10:1, it becomes just 1dB.
Lower ratios (2:1 to 4:1) provide gentle, transparent compression. The dynamic range is controlled without obvious processing. This range works for most vocals, acoustic instruments, and bus compression.
Higher ratios (8:1 to 20:1) create obvious compression character. They're useful for aggressive drum processing, heavy limiting, or intentional "squashed" effects. Ratios of infinity:1 are limiters—nothing exceeds threshold.
5Gain Reduction Math
Gain reduction is the amount by which the compressor reduces signal level. Our calculator shows this in real-time as you adjust parameters. Understanding this math demystifies compression behavior.
Example: Signal at -6 dBFS, threshold at -20 dBFS, ratio 4:1. Signal is 14dB above threshold. Gain reduction = 14 × (1 - 1/4) = 14 × 0.75 = 10.5dB. Output = -6 - 10.5 = -16.5 dBFS.
This calculation shows why compression reduces overall level. You're removing energy from loud portions. Makeup gain compensates, but the dynamic range itself—the difference between loud and quiet—is permanently reduced.
6Makeup Gain Strategy
Makeup gain restores level lost to compression. Without it, compressed signals sound quieter than originals, making A/B comparison misleading—quieter always sounds worse regardless of processing quality.
Match perceived loudness, not peak levels. Compressed audio has higher RMS (average) levels even at lower peaks. Use your ears and meters to find appropriate makeup that enables fair comparison.
Some compressors offer auto-makeup gain. While convenient, automatic settings may not match your intention. Manual adjustment after achieving desired compression character typically yields better results.
7Common Applications
Vocal compression typically uses 3:1 to 6:1 ratios with thresholds catching 6-10dB of the loudest passages. This controls dynamic inconsistencies from natural performance variation while maintaining expressive range.
Drum bus compression often uses faster attack, medium release, and moderate ratios to glue kit elements together. The pumping effect at higher ratios creates the punchy, powerful drum sounds of rock and pop production.
Mix bus compression uses gentle settings (2:1 to 3:1, 1-3dB reduction) to unify the entire mix. This "glue" compression makes separate elements feel like a cohesive whole rather than individual tracks.
8Tips & Best Practices
Start with moderate settings. It's easier to add more compression than to undo over-compression. Begin around 3:1 ratio with threshold catching occasional peaks, then adjust based on what you hear.
Use the calculator to understand before you compress. Input your typical signal levels and experiment with different threshold/ratio combinations. This previewing helps you approach real compressors with intention.
Always A/B with makeup gain matched. Bypass the compressor periodically to verify you're actually improving the sound, not just making it louder. Level-matched comparison reveals compression's true contribution.
Consider multiple stages of gentle compression rather than one stage of heavy compression. Serial compression (2-3dB reduction across several compressors) often sounds more natural than single-stage 10dB reduction.