Audio Compression Cheat Sheet

Definitions Threshold - how loud the signal level must be before the compressor starts working. Ratio - The amount of compression that is applied. E.g., if the ratio is set for 4:1, the input

signal will have to cross the threshold by 4 dB for the output level to increase by 1 dB. Attack - How quickly the compressor engages. Release - How soon after the signal goes below the threshold the compressor stops

engaging. Knee - Determines how the compressor responds to signals after the threshold has been

passed. Hard Knee - engages and clamps the signal immediately Soft Knee - Compression engages more gently as the signal goes further past the

threshold. Make-Up Gain - Provides a boost to the gain, since compression can lower gain slightly. Output - Enables you to boost or adjust the level of the signal output leaving the

compressor.

Chart Notes ●

These are suggestions that can be helpful when mixing, but are by no means hard and fast rules! Every situation and taste is different. Start with these and adjust!

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“Use your ears.” If something sounds good, go with it. Make use of reference tracks often.

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Really be deliberate with your compression choices.

Lighter Compression Table (With threshold, no knee) Instrument

Threshold

Attack

Release

Ratio

Vocal

-8dB

<1ms (Fast)

~40ms

-btwn 1.5:1 & 2:1 -For really bringing vocals out try between 4:1 and 6:1

Bass

-4dB

40-50ms

~180ms

-btwn 2.5:1 & 3:1

Acoustic Guitar -6dB

~150ms

~400ms

-btwn 2:1 & 4:1

Electric Guitar

-1dB

25-30ms

200ms

-btwn 2:1 & 3:1

Kick

-4dB

5-10ms

12-175 ms

-btwn 4:1 & 6:1

Heavier Compression Table (With a knee and auto release times.. set your own threshold) Instrument

Knee

Attack

Release

Ratio

Vocal

Soft

<1ms (Fast)

0.5s/Auto

-btwn 2:1 & 8:1

Bass

Hard

2-10ms

0.5s/Auto

-btwn 4:1 & 12:1

Acoustic Guitar Soft/Hard

5-10ms

0.5s/Auto

-btwn 5:1 & 10:1

Electric Guitar

Hard

2-5ms

0.5s/Auto

8:1

Kick

Hard

1-5ms

0.2s/Auto

-btwn 5:1 & 10:1

Additional Tips for Compression ●

Be wary of over compressing things (especially vocals), unless the style of music calls for it.

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Don’t kill transients. Attack times that are too short (especially on drums) can kill transients. You want those!

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Until you’re incredibly familiar with compression, use one compressor … work on learning it inside and out.

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Set make up gain properly so that when you compress the audio stays the same when you bypass the compressor. Don’t let loudness fool you into thinking it’s automatically better.

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High ratios with high thresholds give a sound that hits harder (think “punch” and “thump.”)

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Low ratios with lower thresholds will tend to offer up an effect that’s softer, adding “warmth” “thickening” and “glue.”

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Avoid low threshold with high ratios unless you want a sound that is very squashed and potentially devoid of any life.

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Important rule: If the gain reduction meter doesn’t return to zero several times each bar, you are most likely over compressing.

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For an awesome pumping sound on a track, utilize a long attack time with a high ratio and threshold.

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Using automatic settings can reduce negative “unnatural” compression effects but can allow you to use too much compression without knowing it.