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 and the quietest portions of the signal (above the noise floor of a system), expressed in dB. Dynamic range can either be increased using an expander or reduced using a compressor.

Definitions of Extron dynamics processors are listed in the subsections, below. Each subsection includes a table that shows setting ranges for each relevant parameter. See the Dynamics Operation section for more information.

AGC

Automatic gain control (AGC) adjusts the gain level based on 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 or below the target level. When a signal reaches the window, gain control begins to scale in a linear fashion toward the target level, in order to achieve smoother results.

Compressor

A 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 by reducing the dynamic range and then raising the output level of the compressor (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 (see the "Limiter" subsection, below), to protect a system or a signal chain from overload.

The ratio of the input level of the signal to the output level determines the reduction in the dynamic range beyond the threshold setting. For example, with a ratio setting of 4:1, for every 4 dB of input the compressor outputs 1 dB 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 effectively removes 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 and opening the path above the threshold to allow signal to pass.

Dynamics Processing Parameters

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

Definitions of dynamics processing parameters are as follows:

• Threshold - This is the level above which compression engages (subject to attack time) and below which compression disengages (subject to release time). For a noise gate (expander), the opposite is true. The noise gate engages below the threshold and disengages above the threshold.

• 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 begins to scale the signal (in a linear fashion toward the target level) to achieve smoother results

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

• Release Time - This is 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 length of time that processing continues after the threshold is no longer met and before release time comes into play

• Maximum Attenuation (Gate only) - The maximum attenuation that can occur after the signal exceeds the threshold.

• Soft Knee - At the point at which dynamic processing engages, a sharp adjustment in input to output level can occur, especially at higher ratios. This point is referred to as the "knee," because the representation on a graph of pre- and post-threshold levels visually resembles a knee joint. Applying Soft Knee reduces the sharpness of this adjustment, smoothing and softening the transition from uncompressed to compressed output levels.