ALLEN & HEATH DIGITAL MIXING SYSTEM User's Guide download pdf (Page 25)

Qu Mixer User Guide 25 AP9372 iss.4

HPF (high pass filter)

The HPF is used to reduce unwanted low frequency

sounds such as vocal popping, wind noise and stage

rumble.

Switch the HPF in using the In key. Use the panel

rotary or screen button and rotary to sweep the cut-off

frequency until you have reduced the unwanted

sound. The filter has a 12dB slope and can be swept

from 20Hz to 2kHz. The violet screen curve shows the

resulting frequency response.

PEQ (parametric equaliser)

The Parametric Equaliser allows tonal adjustment of

the channel sound. It provides independent control of

4 frequency bands:

LF (low frequency)

LM (low mid frequency)

HM (high mid frequency)

HF (high frequency)

Each provides 3 parameters that can be adjusted:

Gain – Boost or cut frequencies by up to 15dB. Centre

0dB is flat response (no affect).

Frequency – Each band can sweep its centre point

frequency across the full range from 20Hz to 20kHz.

This means you can overlap bands and have more

precise control over problem frequency areas.

Width – Each band has a bell-shaped response. The

width of the bell can be varied from a very wide 1.5

octaves affecting many frequencies to a very narrow

1/9

octave affecting a small range of frequencies.

Setting LF or HF to widest position using the screen

rotary changes its response to shelving.

Experiment with the controls to hear their affect on

different sounds. Switch the PEQ in or out using the In

key to compare the sound. It is better to cut rather than

boost frequencies where possible.

Compressor

The Compressor is a powerful tool for controlling the

dynamics of the sound, for example to smooth out a

bass guitar or to narrow the dynamic range of a vocal

to make it more intelligible in a busy mix. At its extreme

setting the compressor can be used as a limiter to

prevent the signal exceeding a preset maximum level.

A compressor works by dynamically reducing the

amount of gain when the signal increases above a

certain threshold. This pulls back loud moments.

Applying ‘make-up’ gain restores the average volume

and also has the effect of bringing up quiet moments.

The result is a reduced dynamic range.

While listening to the signal adjust Thres (threshold) to

set the point at which compression starts. The GR

indicator and red screen meter will start to show that

compression is active. Set Ratio for how much

compression you want from none (1:1) to full limiting

(Inf). A ratio of 3:1 is a good starting point.

Compressor active

GR = Gain Reduction

Touch the curve to turn the colour

fill option on or off.

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ALLEN & HEATH DIGITAL MIXING SYSTEM User's Guide Page 25

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