Dynamic range processors are used to control the dynamics in an audio signal. The term ‘dynamics’ refers to the variations in level. ‘Dynamic range’ refers to the difference between the loudest and quietest parts of the signal. In this article, we’ll look at the different types of dynamic range processors and learn how each one affects the dynamic range of the signals in your mix.
Dynamic Range Processors – Compressors:
Downward compressor: A downward compressor, often referred to simply as a compressor, reduces dynamic range by turning the loud parts of a signal down. Downward compressors utilize a ‘threshold’ parameter. Threshold is used to determine which parts of the signal are turned down and which remain unprocessed. As such, downward compressors turn down any parts of the signal that are above the threshold.
The amount of attenuation applied is controlled by the compressor’s ‘ratio’ parameter. Ratio values are represented in a format that signifies input:output. As such, a ratio of 4:1 means that if the incoming signal overshoots the threshold by 4dB, the compressor will only allow the signal to raise the output level by 1dB. If the signal overshoots the threshold by 8dB, the compressor will only allow the signal to increase in level by 2dB.
Upward compressor: Much like a downward compressor, an upward compressor also reduces an audio signal’s dynamic range. In this instance however, it does so by turning the quiet parts of the signal up. The compressor’s threshold controls which parts of the signal the compressor amplifies. So with upward compression, the compressor will turn up any parts of the signal that drop below the threshold. Just like downward compressors, upward compressors also utilize a ratio parameter. In this instance, the ratio determines how much the compressor will turn the signal up when it falls below the threshold. A ratio of 3:1 means that, if the signal drops 3dB below the threshold, then the compressor will amplify the signal to only 1dB below the threshold. If the signal drops 9dB below the threshold, the signal will be output at 3dB below the threshold.
Dynamic Range Processors – Limiters:
Limiters: A limiter functions in a similar way to a downward compressor in that it reduces dynamic range by turning down any part of the audio signal that overshoots the threshold. A limiter differs however; in that, it turns down any parts of the audio signal that breach the threshold down to the threshold level itself. It does so by using high ratio settings. So regardless of how much the signal overshoots the threshold, the audio signal should not get louder than the threshold level.
Dynamic Range Processors – Expanders:
Downward expanders: Unlike compressors which reduce dynamic range, expanders increase dynamic range. A downward expander increases the dynamic range of an audio signal by making the quiet parts of the signal even quieter. As such, downward expanders turn down the signal below the threshold. The ratio determines the amount of attenuation applied to the signal below the threshold. The expander’s ratio is represented in an input:output format, just the same as the compressor. So with downward expansion, a ratio of 1:3 means that if the signal drops 2dB below the threshold, the signal will be attenuated to 6dB below the threshold.
Upward expanders: Just like a downward expander, an upward expander also increases the dynamic range of an audio signal. But this time, it does so by making the loud parts of a signal even louder. Upward expanders turn the level of any parts of the signal above the threshold up by the ratio amount. Accordingly, a ratio of 1:2 would see a signal that overshoots the threshold by 2dB amplified to 4dB.
Dynamic Range Processors – Gates:
Gates: Gates affect a signal’s dynamic range by turning parts of the signal down, often to the point that they are effectively inaudible or muted entirely. In this respect, they are much the same as downward expanders. But unlike expanders which are attenuated by a ratio amount, gates apply attenuation to a specific decibel amount. The gate’s ‘range’ parameter controls the decibel amount. As such, the gate attenuates any signal which drops below its threshold by the range amount. Accordingly, a range value of -10dB would see the audio signal below the threshold turned down by 10 dB. A range value of -20dB would see the level below the threshold turned down by 20dB. Setting your gate’s range to a value of -80dB effectively mutes any audio signal that falls below the threshold.
Dynamic Range Processors – Duckers:
Duckers: Duckers turn down any part of an audio signal that overshoots the threshold. The ducker attenuates the signal in accordance with its range setting, just like a gate does. As such, a ‘range’ value of -10dB would see the signal that overshoots the threshold turned down by 10 decibels.
Do you use dynamic range processors in your mixes? If so, what do you use them for?
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