About Dynamics

Dynamics processors alter the dynamic range of an audio signal, which, for sound reinforcement, is typically a mic input or program material. Dynamic range is the difference between the loudest to the quietest portions of the signal (above a system’s noise floor), expressed in dB. Dynamic range can either be increased using an "expander," or reduced using a "compressor."

Definitions of Extron® dynamics processors follow. Each section includes a table showing setting ranges for each relevant parameter. See topic, Dynamics Operation, for more information.

AGC

Automatic gain control (AGC) adjusts the gain level based upon the strength of the incoming signal, in order to achieve a more consistent volume. Above a set threshold, weaker signals receive more gain in order to reach a user-defined target level; stronger signals receive less gain or no gain at all.

A "window" range is also applied above and below the target level. When a signal reaches the window, gain control will begin to scale in a linear fashion toward the target level, for the purpose of achieving smoother results.

Compressor

The compressor regulates the level of an input signal by reducing, or compressing its dynamic range above a user-defined threshold. Compression is commonly used to keep mic levels within an acceptable range for maximum intelligibility. Though a compressor effectively makes louder portions of a signal softer, it is used to make softer sounds louder either by reducing the dynamic range and then raising the compressor's output level (referred to as "make-up gain"), or by increasing the input signal and then preventing clipping by reducing the louder portions of the signal. Compression is also used, similar to a limiter, to protect a system or a signal chain from overload.

The ratio of the signal's input level to output level determines the reduction in the dynamic range beyond the threshold setting. For example, with a ratio setting of 4:1, for every 4dB of input the compressor will output 1dB of gain.

Limiter

A limiter regulates the level of an input signal by severely restricting its dynamic range above a user-defined threshold. Limiters are commonly used to prevent clipping, and protect a system against component or speaker damage. Limiters are closely related to compressors but apply much higher compression ratios, usually in excess of 20:1 (often expressed as ∞:1), and usually with a high threshold setting (close to clipping).

Noise Gate

A noise gate is a function of an expander, which is a dynamics processor that expands the dynamic range of a signal below a user-defined threshold. It is generally used to make soft signals softer, and is effective at removing background noise while allowing a stronger signal, above a user-defined threshold, to pass. Using a high ratio of 1:∞, the expander closes the audio path below the threshold, eliminating background noise, opening the path above the threshold to allow signal to pass - hence the term, noise gate.

Dynamics Processing Parameters

The table below shows each Dynamics type, parameters, and typical default settings.

Definitions of dynamics processing parameters are as follows:

Threshold - the level above which compression will engage (subject to attack time), below which compression will disengage (subject to release time). For a noise gate (expander) the opposite is true - the noise gate will engage below the threshold, and disengage above the threshold. For AGC, threshold is the level above which gain control will engage, and below which gain control will disengage.

Gain (AGC only) - the maximum amount of gain that will be applied to a signal, after the Threshold is met, in order to reach or approach the Target value.

Target (AGC only) - the desired average output level, after the signal exceeds the threshold.

Window (AGC only) - the range above and below, equidistant from the Target level, from which gain control will begin to scale the signal in a linear fashion toward the Target level, for the purpose of achieving smoother results.

Attack Time - the time it takes for processing to engage after the signal meets or exceeds the threshold level.

Release Time - the time it takes to return a signal to a normal (unprocessed) level after the signal no longer exceeds the threshold level setting.

Ratio - the ratio of input level to output level after dynamics processing has engaged.

Hold Time - the time that processing continues after the threshold is no longer met, and before release time comes into play.

Max Attenuation (Gate only) - the maximum attenuation that can occur, after the signal drops below the threshold.

Soft Knee - at the point at which dynamics processing is engaged, a sharp adjustment in input to output level may occur, especially at higher ratios. This point is referred to as the "knee," since the representation on a graph of pre- and post-threshold levels visually resembles a knee joint. Applying Soft Knee will reduce the sharpness of this adjustment, smoothing and softening the transition from uncompressed to compressed output levels..