• Compression is a dynamic processor which it can be described as 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 compressors:

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

    2. Attack: How quickly the compressor starts to react once it crosses the threshold.

    3. Release: How quickly the compressor stop 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 compressor responds 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.

  • Types of compressors 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.

    1. Setting It Up: Pull up your mix session and solo your drum bus. Load up your favourite compressor on the drum bus. Here’s a free compressor to start with.

    2. Monitoring Level: Reduce until you can faintly hear your mix.

    3. Adjust Threshold: Exaggerate gain reduction from the compressor until your ear can hear the compression.

    4. Adjust to Slow Attack Time: You’ll be able to hear the transient and punch from your drum kit. The drum sounded tougher, aggressive, projecting strength, weight and authority.

    5. Adjust to Fast Attack Time: You’ll have more difficulty hearing the transient and punch from the drums. The drum sounded softer, mellower, smoother and the sustain of the drums will come up.

    6. Adjusting Monitoring Level to Hear Release Time Changes: +8 to +10 dB of monitoring level increase so that you can hear the sustain of the drums.

    7. Adjust to Fast Release Time: More defined individual hits on kick, snare & cymbals. Shaping the envelope of the drum sounds in a musical way.

    8. Adjust to Slow Release Time: The kick sounded flappy, tighter snare sound, cymbals sounded washy & distant.

    9. For detailed explanation, watch this brilliant video done by Gregory Scott.