dbx Pro 160A manual De-Essing, Increasing Sustain, Multi-Way Speaker Systems

dbx 160A COMPRESSOR / LIMITER

The converse of the above EQ technique may be used: dipping the equalizer bands causes any sound with dominant energy in the affected register to pull the level up because the 160A will detect a need for less compression.

De-Essing

To apply de-essing to vocals (i.e., a reduction of sibilance), use a parametric equalizer in the level detector circuit and set it for high frequency boost in the specific frequency range where the vocal ÒhissÓ or lisp occurs (generally in the 4-6kHz region). This pre-emphasizes the already ÒhissyÓ vocal input to the detector. Used in conjunction with a moderate to high THRESHOLD and COMPRESSION RATIO, this arrangement greatly attenuates the ÒessingÓ without affecting the basic sound quality or balance of the voice. While it is true that all frequencies are lowered in level when the compressor is trig- gered, generally the ÒsssÓ sound occurs alone, before or after the dominant tone in the voice.

Increasing Sustain

To increase the sustain of a musical instrument (e.g., a guitar or bass), use an equalizer in the level detector circuit and boost the EQ in the dominant frequency range of the instrument. Set the 160A to Hard Knee mode, with a fairly low THRESHOLD and a moderate COMPRESSION RATIO.

Multi-Way Speaker Systems

If a single compressor is to be used with a multi-way speaker system (i.e., before the crossover, after the EQ), the system operator is faced with the problem of keeping levels below the point of damage of the most sensitive part of the system. If, for example, mid-range drivers are frequently damaged, the whole system must be operated at a lower sound-pressure level, or additional mid-range drivers must be added. By inserting an equalizer in the detector path to the 160A, it can be made more sensitive to frequencies in the range handled by the sensitive drivers. The system can then be run at higher lev- els and will only be dropped back when damaging signals are present.

Using a Filter in the Level Detector Circuit

The results of inserting a filter in the level detector circuit are basically the same as obtained with an equalizer, as previ- ously described. Those frequencies passed by the filter are subject to compression (or at least they are subject to consider- ably more compression than those frequencies outside the passband). Because a passive filter can have insertion loss, it may be necessary to lower the 160A's THRESHOLD setting to maintain a given amount of gain reduction within the filter passband; this can be determined by monitoring the 160A's THRESHOLD LEDs.

Pre-Emphasis for Broadcast Applications

By inserting a pre-emphasis filter network in the detector path of a 160A processing pre-emphasized audio, higher levels can be run within the headroom limitations of the broadcast chain.

Anticipated Compression (Sidechain Application)

By feeding the program directly to the 160A's detector input and sending the audio signal through a delay line before the audio input, the unit can anticipate the need for a gain change. With some experimentation, the effect can be that of zero attack time at a given frequency. Additional signal delays beyond this zero time will then cause the compressor to finish reducing the gain before the leading edge of the loud passage even enters the signal input. This will suppress the program material preceding this loud passage. The 160A will then begin to release (recover from compression) before the loud pas- sage has ended.

SOURCE

160A

INPUT OUTPUT

DETECTOR INPUT

OUTPUT

DELAY

Figure 5: Anticipated Compresion

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