lesson
Updated 6 days ago · 2 views
Ever wonder how a vocalist's whisper and full-throated belt can sit at the exact same perceived level in a modern mix without clipping or disappearing?
A compressor acts like an automated fader with lightning-fast reflexes, narrowing a track's dynamic range — the decibel difference between its quietest detail and loudest peak.
To tell the compressor when to step in, we start by setting a trigger point.
Threshold: Setting the Trigger Level
The threshold is the exact input level, measured in decibels (dB), at which gain reduction begins.
Any incoming audio below this set level passes through completely untouched at unity gain (1:1), while any signal crossing above it triggers compression.
📊A clean visual diagram of an audio waveform passing through a horizontal threshold line. The threshold line is dashed orange at -18 dBFS. Audio peaks that stay below -18 dB are colored cool blue (untouched). Audio peaks that shoot above -18 dB are highlighted in coral red with a downward arrow showing 'Gain Reduction'. Light background (#f8fafc), dark navy text (#1e2945), sleek meters on the right.
Once a peak crosses that threshold boundary, how aggressively should the compressor squeeze it down?
Ratio: Determining the Amount of Squeeze
The ratio determines how much gain reduction is applied to any signal exceeding the threshold by comparing input decibels to output decibels.
At a 4:1 ratio, for every 4 dB the input signal exceeds the threshold, only 1 dB is allowed to pass to the output.
📊A standard compressor transfer curve graph (Input dB on X-axis from -40 to 0, Output dB on Y-axis from -40 to 0). A threshold knee point is marked at -20 dB. Below -20 dB, a single line runs at a 45-degree angle (1:1 uncompressed). Above -20 dB, show three distinct slope lines: 2:1 (gentle slope, teal), 4:1 (moderate slope, blue), and 20:1 / Limiting (nearly flat horizontal line, purple). Interactive toggle or clean legend showing each ratio clearly.
How do we predict the exact output level and gain reduction mathematically?