In music production, ratio is a crucial setting within an audio compressor that determines the amount of compression applied to a signal once it exceeds a set threshold. It dictates how aggressively a compressor will reduce the dynamic range of an audio signal.
Understanding Compression Ratio
The ratio setting is typically expressed as X:1 (e.g., 2:1, 4:1, 10:1). This number indicates the relationship between the input signal level exceeding the threshold and the output signal level that results.
- How it works: For every X decibels (dB) that an audio signal goes above the threshold, the output signal will only be allowed to increase by 1 dB above that threshold.
- Example: A ratio of 2:1 indicates that if a signal exceeds the threshold by 2 dB, it will be attenuated so that it only exceeds the threshold by 1 dB. Similarly, if a signal is 4 dB above the threshold with a 2:1 ratio, it will be reduced to only 2 dB above the threshold in the output.
- Impact: A higher ratio means more aggressive compression, resulting in a more significant reduction in dynamic range. A lower ratio provides a more subtle, gentle compression.
Compressors are fundamental tools for shaping the dynamics of individual tracks and entire mixes. Learn more about the basics of audio compression to understand its broader context.
Interaction with Other Compressor Parameters
While ratio is central, its effect is always in conjunction with other compressor settings:
- Threshold: This defines the level (in dB) at which the compressor starts to engage. The ratio only applies to signals above this point.
- Attack: Determines how quickly the compressor reacts and applies compression once the threshold is crossed.
- Release: Controls how long it takes for the compressor to stop compressing after the signal falls back below the threshold.
- Make-up Gain: After compression reduces the overall volume, make-up gain is used to restore the signal to a desirable listening level, compensating for the reduction.
Common Ratio Applications and Types
Different ratio settings are used for various purposes in music production, from subtle dynamic control to aggressive leveling.
| Ratio Range | Description | Common Applications |
|---|---|---|
| 1.5:1 to 3:1 | Low Ratios: Gentle, transparent compression. | Gluing elements together, subtle vocal leveling, overall mix bus. |
| 4:1 to 8:1 | Medium Ratios: Noticeable but natural control. | Taming dynamic vocals, electric guitars, bass guitars, snare drums. |
| 10:1 to 20:1 | High Ratios: Aggressive leveling, limiting. | Overheads, room mics, drums for punch, transient control, limiting. |
| ∞:1 (Infinity:1) | Limiting: Brickwall, no signal exceeds threshold. | Mastering (peak limiting), protective limiting on individual tracks. |
Practical Insights into Using Ratio
- Vocals: A common starting point for lead vocals is a ratio of 3:1 to 5:1. This helps to smooth out volume fluctuations, keeping the vocal consistent without sounding overly processed. For more aggressive pop vocals, you might go higher (e.g., 6:1 or 8:1).
- Drums:
- Snare/Kick: Higher ratios (e.g., 6:1 to 10:1) with fast attack and release can be used to control transients and add punch.
- Overheads/Room Mics: Lower ratios (e.g., 2:1 to 4:1) can gently balance the overall drum sound.
- Bass Guitar: A ratio of 4:1 to 6:1 is often effective for making the bass sound more consistent and present in the mix, ensuring every note has a similar perceived volume.
- Mix Bus (Stereo Master): Gentle ratios (1.5:1 to 2:1) are typical here. The goal is often to "glue" the entire mix together, adding cohesion without squashing the overall dynamics. This requires very subtle application.
Experimentation with ratio, alongside threshold, attack, and release, is key to achieving the desired dynamic response for each element in your mix. Mastering the use of compression ratios allows producers to sculpt the energy and feel of their music, ensuring clarity and impact.
