Symetrix airTools 6200, User Manual

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User’s Guide

6200 Digital 

Voice Processor

To download the latest version of 6200 Designer, a Windows GUI 

application interface for the 6200, go to: www.airtoolsaudio.com

TM

Symetrix

Engineered by

EXPANDER:

An expander reduces the gain of lower level signals thereby increasing the total dynamic range. Above a user defined 

threshold setting, signal levels remain unchanged. Below threshold, signals are reduced by some degree. An expander 

reduces the level gradually for decreasing input level. An expander can be used to reduce room noise during pauses in speech 

or reduce noise floor during pauses in program.

Controls:

Bypass/Enabled - When bypassed, the input is sent unmodified to the output. When enabled, the module processes the signal.
Expander Threshold - The level that the signal must exceed to open the expander (let it pass signal).
Expander Ratio - The slope of the gain curve below the threshold point. A high ratio setting begins to approximate the action of 

a gate.
Gain Reduction (Meter) - A gain reduction meter is provided so that the effect of the expander can be observed (present on 

Threshold and Ratio menus).
Expander Attack - The duration of the input signal, over threshold, required to open the expander. Faster attack times let 

shorter transients open the expander.
Expander Release - The amount of time required for the gain to return to the below-threshold value after the input signal falls 

below threshold.

COMPRESSOR:

A compressor reduces the dynamic range of signals above a user determined threshold. Signal levels below the threshold 

remain unchanged. A compressor can be used to tame transient spikes in audio sources as well as reducing dynamic range to 

control wildly varying levels while increasing intelligibility.

Controls:

Bypass/Enabled - When bypassed, the input is sent unmodified to the output. When enabled, the module processes the signal.
Compressor Sidechain - Determines the mode of the compressor module (Compressor or AGC). Certain controls are only 

applicable within specific modes.
Compressor Threshold - The signal level above which the compressor begins reducing the gain. Visually, the point at the 

knee (bend) in the input/output curve. For peak stopping, set the threshold just below the peak level that you want to stop. For 

dynamic range reduction, pick a threshold setting that results in a few dB of gain reduction indication with the signal levels that 

you are interested in.
Compressor Ratio - The ratio determines the degree of output change for an above threshold change in the input. Generally 

ratios under 10:1 are considered compression while those above 10:1 are considered limiting.
Gain Reduction (Meter) - A gain reduction meter is provided so that the effect of the compressor can be observed (present on 

Threshold and Ratio menus). It indicates the amount of gain reduction that the compressor is currently applying. This meter is 

pre-output gain, meaning changes to compressor output gain do not effect this meter.
Compressor Attack - The speed with which the compressor begins the gain reduction process. Although your intuition tells you 

that you want the fastest possible attack time, your ears will tell you otherwise. Too fast attack times strip transients of their 

edges, dulling the sound. Remember that momentary (brief) clipping is inaudible. Faster attack times allow shorter transients 

to initiate gain reduction. On the other hand, too long attack times can allow short transients to pass unchanged, which may 

defeat the purpose that the compressor was intended for.
Compressor Release - The release time determines the moment-to-moment gain change in the compressor. Fast release 

times raise the subjective level, while slow release times are more useful for keeping levels under control. Very fast release 

times can cause audible distortion, especially with low-frequency content.
Compressor Knee - The knee setting determines the compression ratio during the transition from linear (below threshold) to 

compressor operation. A soft knee makes this change gradually, while a hard knee makes an abrupt transition. A soft knee 

curve may require several dB of gain reduction before the actual compression ratio has reached the set value. For general 

compression, use the soft setting. For limiting, use the hard setting.
Compressor Makeup - The makeup gain controls the output gain of the module. If the compressor is reducing the signal level 

significantly, a boost in the output gain may be required to maintain perceived volume.
Sidechain High Pass - A 150, 300 or 600 Hz side chain high pass filter can be invoked in order to deter low frequency energy 

from triggering expander/compressor action and the resultant unwanted gain reduction.
Lookahead Delay - A lookahead delay can be enabled which allows the module to better predict changes to incoming levels 

and thus provide better dynamics processing. Enabling this delay results in an extra 2 ms processing delay.

DSP Modules... 

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