SYMETRIX 528E
Owner's Manual

528E

Keep in mind that the COMP THRESHOLD becomes a function of the amount of overall gain through the equalizer, including the boost. This technique can be used with any frequency that can be controlled by the equalizer.

Using Sidechain EQ to Enhance Expander Action
Since the expander can only discriminate between different levels (not different sounds), it can be fooled by signals whose levels are nearly the same, even if the frequency content of those signals is fundamentally different. When the 528E�s expander is used to shut out unwanted sounds, any signal that exceeds threshold will trigger the expander. When unwanted signals trigger the system, it�s often possible to eliminate the false triggering by equalizing the control signal. For example, if low frequency signals transmitted through a desk or podium are triggering the 528E�s expander unnecessarily: With an equalizer in the sidechain, remove the low frequencies from the control signal, and/or boost the higher voice range frequencies. When the offending frequencies are removed, and the relative level of the desired frequencies is increased, the expander can tell the difference between the wanted and unwanted signals. Use this technique in any situation where levels are nearly the same, but the fundamental frequencies involved are different. Note The ability of the expander to discriminate between wanted and unwanted signals is determined in part by mic technique. Be particularly careful of high frequency sounds entering the side or rear pattern of a cardioid mic. Most cardioids exhibit a sharply rising off-axis response characteristic at higher frequencies. Check the off-axis curve (the lower one) in the manufacturer�s literature. If there�s only a 3dB to 6dB difference between the on-axis (front) response and the off-axis (side or rear) response in the 5kHz to 10kHz region, high frequency sounds will be picked up by the side or back of your mic. Use the mic�s directional pattern to keep other sources as far off-axis as possible - do everything you can to extract all the source-to-source discrimination possible through good mic technique. The sounds picked up by individual mics must be primarily the sound of the desired signal, or the expander won�t be able to tell the difference.

Using Reverb or Effects
Effects usually require another mixer input for effects return. However, the 528E�s patching connections can be used to feed a signal to the effects unit, and the output stage input can be used to return the effects signal to the 528E�s output. The only requirement is that the effects device have a mix control to set the direct/effects signal mix. If you need a hookup diagram, you�ll �nd one in Figure 7-4.

Vocal Processing - Recording and Reinforcement
The 528E handles a wide variety of program material with ease. When recording vocals, the undesirable side effects that usually result from high ratio comp/limiting, like headphone leakage and room noise, can be reduced with the 528E�s interactive expander processing. During mixdown the 528E not only provides compression, but also eliminates the noise that often accompanies vocal tracks that are processed with high frequency EQ, compression, or both. In sound reinforcement situations, if the threshold has been set correctly, the expander will attenuate whenever a mic is not in use, eliminating extraneous pickup of stage sounds, and reducing feedback from monitor speakers. The operating principle is the same for both the recording and reinforcement situations.

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