A compressor acts like an automatic volume control, turning down the volume of a signal if it gets too loud. This reduces variation between loud and quiet passages, as it automatically reduces the level when the sound goes above a set volume, the threshold. You can then turn up the overall level to make up the level drop and make the sound louder.
You can use a compressor to help even out a performance, preventing a signal from clipping and/or disappearing in the mix, or you can use a compressor to give your sound a whole new sonic character.
The Red 3 Compressor is modelled on the legendary Focusrite Red 3 hardware compressor. The Red 3 plugin (as with the original Red 3 compressor) has a warm, musical sound, and will provide sensitive compression to a wide range of musical sources without compromising the integrity of the original recording.
The controls are as follows:
The dial in the bottom-left of the plugin window (INPUT) lets you control the level of gain at the plugin's input. The gain range is -18 dB to +18 dB. When the dial points vertically upwards (in the centre), 0 dB of input gain is applied.
ATTACK determines how quickly compression is applied once the level of the source signal has risen above the threshold. The attack time is fastest when fully anti-clockwise, making the compressor react to the peak levels of the signal. This is sometimes desirable but can cause unwanted “pumping” of steadier low-level components of the signal, due to short transients.
Rotating the dial clockwise will make the attack time slower, causing the compressor to ignore short transients and respond more to the average loudness of the signal.
Faster attack times are useful on instruments such as a slapped bass guitar, where the compressor is being used to create a very ‘punchy’ sound. Slower attack times are more suitable on vocals or instruments where the compressor is required to provide a more subtle control of signal level.
RELEASE sets how quickly the compression is removed once the level of the source signal has fallen below the threshold. The release time begins at 0.1 seconds (fully anti-clockwise). This is useful for rapidly varying signals to avoid compressing the beats that follow, but can result in distortion on more sustained sounds.
Clockwise rotation continuously increases the release time. This gives a smoother effect. The maximum release time is four seconds.
The setting of the RELEASE control will not affect the signal when the AUTO RELEASE button is engaged, as outlined below.
When you turn on AUTO RELEASE, the release curve response is set by the sound and the auto-release calculation.
The release rate varies to suit the dynamics of the signal. This is especially effective on complex sounds and enables fast attack times without hearing any “pumping” artefacts. When AUTO RELEASE is on, you can still move the RELEASE knob, but the position and release value shown on the release knob does not affect the release time.
The RATIO dial determines the rate at which compression is applied to a signal with increasing input and is the ratio of change in input level compared to change in output level. The control gives a continuous range of 1.5:1 to ∞:1
Lower ratio settings will be softer, and provide gentler control over the signal levels. As the ratio increases, however, the compression will become harder and more noticeable. At very high ratios, the compressor will behave in much the same way as a limiter.
The THRESHOLD control sets when the compression starts, with a range of –50 dB to –10 dB. The lower the threshold, the more the signal is compressed. Setting a higher threshold leaves quieter passages unaffected, as only passages that exceed the threshold are compressed. When the input/output meter is set to INPUT, threshold is shown via the red needle as explained above.
There are two level meters on the Red 3 Compressor; the input/output meter (on the left) and the GAIN REDUCTION meter (on the right) of the plugin panel.
The input/output meter has two possible sources, selected by toggling the INPUT/OUTPUT switch beneath the meter.
When set to INPUT, the meter displays the signal level immediately after the INPUT gain control. The red needle in the meter also moves to show the threshold value selected by the THRESHOLD control. This helps show when the input signal exceeds the threshold, and if compression is being applied.
Note
The Red 3 Compressor is a ‘soft knee’ compressor. As the input signal approaches the threshold point, gentle compression is applied. The result is a smoother, more transparent compression. This also means that when the signal level on the meter is slightly below the red needle, a small amount of gain reduction will still be applied.
When set to OUTPUT, the meter displays the signal level immediately post the DRY/WET control in the signal chain. In this mode the red needle will not operate, this is because the compression is applied to the input signal rather than the output signal.
The GAIN REDUCTION meter displays the amount the compressor is attenuating, or reducing, the signal. It works from right to left.
After the overall level has been reduced by compression, the MAKE-UP GAIN dial allows you to increase the output level. Up to 40 dB of make-up gain is available.
The DRY/WET control lets you mix your processed (compressed) and unprocessed signals, to help you maintain more of the dynamics of the source. When fully anti-clockwise (DRY), only the unprocessed signal will be audible. When fully clockwise (WET), only the compressed signal will be heard. When the dial points directly upwards (50/50), equal amounts of processed and unprocessed signals are mixed.
This simulates parallel compression: the common practice of mixing compressed and uncompressed signals on two separate channels of a mixing console. It lets you reduce the dynamic range of the signal without creating an overly ‘squashed’ sound.
This can be particularly useful when compressing drums, as a very heavily compressed signal, can be blended with the uncompressed signal. The DRY/WET control can also be used to great effect on signals where a very subtle compression is needed, such as on vocals.