Output; Gain And Polarity; Delay; High And Low Pass Filters - EM Acoustics Di06 Product User Manual

Output

Gain and Polarity

The Output 'strip' in the gain/delay view of the System Engineer panel allows you to increase or
decrease the relative signal gain for any given output. The Gain value may be adjusted in 0.2dB steps
from -40dB to +20dB. You can also change the polarity of the output from normal to reverse and
mute it.

Delay

The Output 'strip' also allows you to control the amount of delay associated with that output channel,
delay
and is adjustable from 0 to 998ms. The parameter is adjustable in fine steps at low values; the
adjustment becomes progressively coarser as the value increases.

High and Low pass Filters

The xover view of the System Engineer panel provides access to High pass and Low pass crossover
filtering for the output. Filter type is selectable from 1 order, Butterworth, Bessel, Linkwitz-Riley,
st
Hardman and LIR Linear Phase. Filter slopes of up to 8th order or 48dB / octave are provided. Not all
filter types are available in all slopes. For example 18dB / octave Linkwitz-Riley filters cannot be
selected because they do not exist.
The Hardman type filter is always described by its order as the filter becomes progressively steeper
rather than following a linear slope so a dB/octave description is not accurate.

LIR Crossover Filtering

"Linear Impulse Response" (LIR) crossover filtering gives a Linear Phase crossover which has a
constant delay regardless of frequency (unlike other types of crossover which delay different
frequencies to a different extent, thus smearing the arrival time). The LIR crossover can thus be
described as having a flat Group Delay response, and thus entirely free of Group Delay Distortion, this
is exactly the same as can be provided by common FIR filtering but without the complications and
disadvantages inherent with the FIR technique.
The shape of the LIR crossover filter is similar to a 4 order Linkwitz-Riley filter, and maintains zero
th
phase difference between the adjacent bands across the crossover region to keep the polar response
rock steady.
Note that very narrow bandwidths are not possible with this crossover type. If the Low Pass
frequency is too close to the High Pass frequency, then the filter will 'mute'.
Linear Phase filtering necessarily introduces delay; the laws of physics demand it. To keep this delay
to a minimum, it is recommended that more conventional crossover shapes (such as Linkwitz-Riley)
are used for the very lowest frequency high-pass edge, particularly if this is less than perhaps 100Hz,
which is well below the frequency thought to cause audible 'Group Delay Distortion'.
This constant delay will depend on the lowest high-pass frequency used in the crossover filters in a
given Drive Module.
Also see the section on Latency Delays.

Parametric Equalisation and All-Pass Filters

Equalisation is accessed by clicking the EQ navigation button in the System Engineer panel. There are
ten different EQ filters; two shelving filters and eight parametric filters. Parametric filters are defined
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