XTA 5 Series - Manual (Page 62)

Page 62
5 Series 5 Series 5 Series 5 Series Operator’s Manual
Elliptical filters
InA Input A HPF:1/~~ InA Input A HPF:1/~~ InA Input A HPF:1/~~ InA Input A HPF:1/~~
1k00Hz HP Ellip 1k00Hz HP Ellip 1k00Hz HP Ellip 1k00Hz HP Ellip
Remember – to change filter types, press BYPASS BYPASS BYPASS BYPASS to bypass
the filter, and then use ENTER ENTER ENTER ENTER to select the filter type.
The elliptical filter has adjustable frequency only. This sets the
3dB point of the filter which features a steep roll-off (of approx
36dB/Octave down to one Octave above (or below in the case
of a HPF) the turnover frequency.
However, the gain does increase again above this frequency to
settle at 12dB down from 0dBr. This filter can be used in
conjunction with the standard crossover filters to produce
sharper roll-offs than would be otherwise achievable.
The use of this filter is explained in the following example.
The graph shows three different low pass filter shapes.
Number 1 is a standard 24dB/Octave Linkwith-Riley curve.
Number 2 is a 48dB/Octave Linkwitz-Riley.
As can be seen, number 2 is significantly steeper in roll-off
than number 1, as would be expected.
However, number 3 is a 12dB/Octave Butterworth filter with
an Elliptical Low Pass filter following it. This produces a
combined roll-off very close to that of the 48dB/Octave (with
the side effect of the response rising again after the initial drop
from the pass band).
To produce a crossover filter of this shape it is simply a case of setting the low (or high) pass filter for that output to the
desired crossover frequency, and selecting a 12dB Butterworth response:
OP1 Output 1 HPF /~~ OP1 Output 1 HPF /~~ OP1 Output 1 HPF /~~ OP1 Output 1 HPF /~~
250Hz Butterworth 12dB 250Hz Butterworth 12dB 250Hz Butterworth 12dB 250Hz Butterworth 12dB
Then select a parametric section on the same output, and modify its behaviour (using the ENTER ENTER ENTER ENTER key) until the
corresponding HPF Elliptical filter is selected. Set the turnover frequency of this filter to be the same as that of the
crossover filter. Make sure you chose a high pass elliptical to work with a high pass crossover, and low pass elliptical to
work with a low pass crossover.
InA Input A HPF:1/~~ InA Input A HPF:1/~~ InA Input A HPF:1/~~ InA Input A HPF:1/~~
250Hz HP Ellip 250Hz HP Ellip 250Hz HP Ellip 250Hz HP Ellip
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