• Compression is the process of adjusting the volume knob automatically when an audio signal crosses a set threshold, bringing up the quiet part and reducing the loudest part to a quieter level.

  • Reasons to use compression:

    1. Ensuring volume consistency throughout the whole audio track.

    2. Bringing down peaks to produce more headroom.

    3. Glue different instrumentations together.

    4. Adds a certain characteristic to the audio signal.

  • Basic Controls Found in Compressor:

    1. Threshold: The starting line for compressor to reduce gain.

    2. Attack: How quickly the compressorstartsto react once it crosses the threshold.

    3. Release: How quickly the compressorstop reacting once it drops below the threshold.

    4. Ratio: How aggressive a compressor reduces gain once it crosses the threshold.

    5. Knee: How quickly a compressorresponds to incoming audio signal when approaching threshold value.

    6. Makeup Gain: Gain applied to compensate the gain reduction from compression.

    7. Sidechain Filter: Set the compressor to listen and react only to the intended frequency range.

  • Common compressor types and its examples:

    1. Voltage Controlled Amplifier, (VCA) Compressors: Uses a controlled signal to determine how much gain reduction is applied. Known for their precision and transparency. Often used for glueing a mix. Eg. SSL G Bus Compressor, API 2500 Compressor.

    2. Field Effect Transistor (FET) Compressors: Rely on transistors for gain reduction. Known for their aggressive character. They react quickly, adds brightness, presence, and gritty characters when pushed, which are great for highly transient materials. Eg. 1176.

    3. Optical (Opto) Compressors: Uses a light-dependent resistor and a light source to control gain reduction. They provide musical, natural and smooth response, great for vocals and instruments that needed gentle compression. Eg. Teletronix LA-2A.

    4. Variable-Mu (Vari-Mu)/Tube Compressors: Rely on vacuum tube for gain reduction control. They have slower response (compared to FET and VCA Style Compressors) to catch transient. Excel at adding warmth and harmonically rich sound, providing smooth cohesion to a mix. Eg. Fairchild Compressor, Manley Variable-Mu Compressor.