FIR on Output not as Xover filter, using imported coefficients.
If the user would like to use an IIR filter as Xover, being necessary in example a cutting frequency
below 250Hz, but still having available the FIR in the Xover section, a trick can be used for getting the
result.
Particularly, we coujld say that we have three p[ossible way of using the FILTERS of the output
channels.
1. 7 bands parametric Eq + IIR Xover (no FIR used): the Xover cutting frequencies can be set
everywhere by the user, without limitation
2. 7 bands parametric Eq + FIR Xover (no IIR used): the Xover cutting frequencies can be set
everywhere above 250Hz/300Hz by the user, no reasonable slopes can be achieved with the FIR for
lower cutting frequencies.
3. If necessary to set a cutting Frequency for a Lp or Hp below 250Hz, but still we'd like to have the IFR
available, eventually for working with imported coefficients, a trick for getting the result can be used.
If we'd like to combine the IIR filters for Hp/Lp for low frequencies and still have FIR filters available,
let say for further filtering, as PEQ one or any sort of phase configuration, then the user can operate in
the following way, "sacrificing" some of the filters of the PEQ: the user can create the Low Freq Hp or
Lp, using the variable Q Hp/Lp filters available in the Peq. They are in cascade, therefore, for a Hp/Lp
48dB/Oct, you can use 4 of them leaving still 4 more filters available.
Would be necessary to consume all of them for a Bp with 48dB/Oct Hp/Lp...but is a very rare case.
Anyway, in this way, the user can have the IIR Hp or Lp, plus 4 more filters for Peq correction still of
Low Freq and an available FIR 512Taps which can be used as the user desires if uploading the
coefficients from an external source.
The user can see each one of the PEQ Filters as a IIOrd Cell, which if set as Hp or Lp with variable Q,
can give a 12dB/Oct filter.
In example, setting the Filter N1. of the PEQ, set as Lp-Q at 1kHz and with Q=0.7, then can be gotten
a 12dB/Oct Butterwoth Lp Pass with 1kHz Cutting Frequency.
Selecting now the second filters also as Lp-Q, and also with 1kHz cutting Frequency, and setting the Q
of the first filter to 0.55 and the Q of the second to 1.3, then a 4th order Butterworth can be set up.
