Ashly mXa-1502 12-Channel 4-Zone DSP Mixer-Amplifier - Manual (Page 22)

Crossover (output only)
Crossover blocks can be placed on both
speaker and Aux output channels. A high-pass
and low-pass frequency is applied for each
crossover filter, along with filter type, to band-
limit the signal for that output.
Outputs populated with a crossover block will
be shown on the edit screen for clear visual
representation of the crossover settings. Select
any output to edit its filter parameters.
The default filter type is 24dB/oct Butterworth,
but can be changed to any of the following:
Available Filter Types:
Bessel
: 2nd, 3rd, 4th and 8th order (12, 18,
24,48 dB/octave)
Butterworth : 2nd, 4th and 8th order (12, 24,
48dB/octave)
Butterworth/Linkwitz : 3rd order (18dB/oct.)
Linkwitz : 2nd, 4th and 8th order (12, 24,
48dB/octave)
Linkwitz Notch : 4th and 8th order (24, 48dB/
octave)
The following details summarize filter types
offered:
Butterworth
Butterworth filters individually are always
-3dB at the displayed crossover frequency
and have a "maximally flat" passband and
sharpest transition to the stop-band. When
a Butterworth HPF and LPF of the same
corner frequency are summed, the combined
response is always +3dB. Note that when
12dB/octave Butterworth HPF and LPF filters
are used to create a crossover, the polarity of
one of the outputs may need to be inverted to
compensate for the phase shift of the filter.
Bessel
These filters as implemented in Ashly devices
are always -3dB at the displayed crossover
frequency. Bessel filters have a maximally
flat group delay. Stated another way, Bessel
filters have the most linear phase response.
When a Bessel HPF and LPF of the same
corner frequency are summed, the combined
response is +3dB for 12dB/oct, 18dB/oct, and
48dB/oct Bessel filters, and -2dB for 24dB/
oct Bessel filters. One of the outputs may need
to be inverted when using either 12dB/oct
or 18dB/oct Bessel HPF and LPF's to create a
crossover to compensate for the phase shift of
the filter.
Linkwitz
The 12 dB/oct, 24dB/oct, an 48dB/oct
Linkwitz-Riley filters individually are always
-6dB at the displayed corner frequency.
When a Linkwitz-Riley HPF and LPF of the
same corner frequency are summed, the
combined response is always flat. With 12dB/
oct Linkwitz-Riley crossover filters, one of the
outputs must be inverted or else the combined
response will have a large notch at the
crossover frequency.
Linkwitz Notch
4th and 8th order filters are offered.
Crossover Notes
When used in a crossover, filter type will
affect the way adjacent pass-bands interact
near the crossover point. When electrically
summed, 24dB/octave Linkwitz-Riley filters
produce a flat transition through the crossover
region, assuming that the HPF and LPF are
set to the same corner frequency. This makes
24 dB/octave Linkwitz-Riley filters quite
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mXa-1502 • Operating Manual Ashly AquaControl™ Software