FIR Designer M : Channels – IIR Filters
IIR filters, used for equalisation and/or crossovers, can be set on this view. Common filter prototypes – see list below – are available and the number is unlimited.
| Input | When checked, the filter is applied on the input of the multi-way – prior to the split to output channels – and the filter will appear in the IIR Filters list on all output channels. |
IIR Filtered Response
This plot shows the magnitude and phase for all preceding tabs up to, and including, the IIR Filters, applied to every channel, and the combined system response. The channel target response is also shown.
Series Capacitor Calculator
Many active multi-way loudspeaker systems include a series capacitor on the HF driver to provide some protection from unintended LF energy. This tool can be used to calculate the 1st order HPF corner frequency from a nominal impedance and capacitor value, or calculate the capacitor value from a nominal impedance and desired HPF corner frequency.
A first order HP filter, with the indicated corner frequency, can be added to the IIR Filters list to emulate the magnitude and phase behaviour of the capacitor.
This first order filter will be included in the IIR Filters count on the System Export tab, and in exported summary files.
Care must be taken not to put this filter into the speaker processor, since the capacitor provides this “filtering” function.
IIR Filter Prototypes
There are five IIR filters modes.
General
To switch between BW and Q, go to the Preferences dialog, Global Preferences and Filter definition.
| Parametric | Parametric band push or cut filter with adjustable frequency, BW/Q and gain. (2nd order) |
| Low Shelf, High Shelf | Low and high shelf filters with adjustable frequency, BW/Q and gain. (2nd order) |
| LPF Bessel, HPF Bessel | Low and high pass Bessel filters with adjustable corner frequency and order (1 to 8; 6 dB/oct to 48 dB/oct). |
| LPF Butter, HPF Butter | Low and high pass Butterworth filters with adjustable corner frequency and order (1 to 8; 6 dB/oct to 48 dB/oct) |
| LPF VarQ, HPF VarQ | Low and high pass 2nd order with adjustable corner frequency and BW/Q. |
| LPF Cheb1, HPF Cheb1 | Low and high pass Chebshev Type 1 filters with adjustable corner frequency, pass-band ripple (dB) and order (1 to 8; 6 dB/oct to 48 dB/oct). |
| LPF Cheb2, HPF Cheb2 | Low and high pass Chebshev Type 2 filters with adjustable corner frequency, stop-band attenuation (dB) and order (1 to 8; 6 dB/oct to 48 dB/oct). |
| LPF Ellip, HPF Ellip | Low and high pass Elliptic filters with adjustable corner frequency, pass-band ripple (dB), stop-band attenuation (dB) and order (1 to 8; 6 dB/oct to 48 dB/oct). |
| LPF LR, HPF LR | Low and high pass Linkwitz/Riley filters with adjustable corner frequency and order (2, 4, 6 & 8; 12 dB/oct, 24 dB/oct, 36 dB/oct & 48 dB/oct). |
| LPF NTnc, HPF NTnc | Low and high pass Neville Thiele notched crossover filters with adjustable corner frequency, side-lobe attenuation (dB) and order (4, 6 & 8; 24dB/oct, 36 dB/oct & 48 dB/oct). |
| APass | All-pass filters with adjustable centre frequency, order (1 or 2) and BW/Q (for 2nd order). |
Linea Research
Linea Research filters use BW and ignore the Preferences dialog, Global Preferences and Filter definition setting.
| LPF and HPF 1st Order | 1st order low and high pass filters, equivalent to Butterworth 1st order filters. |
| LPF and HPF 12 dB, 18 dB & 24 dB Bessel | Low and high pass Bessel filters with adjustable corner frequency and selectable order (2, 3 & 4; 12 dB/oct, 18 dB/oct & 24 dB/oct). |
| LPF and HPF 12 dB, 18 dB, 24 dB & 48 dB Butter | Low and high pass Butterworth filters with adjustable corner frequency and selectable order (2, 3, 4 & 8; 12 dB/oct, 18 dB/oct, 24 dB/oct & 48 dB/oct). |
| LPF and HPF 12 dB, 24 dB & 48 dB LR | Low and high pass Linkwitz/Riley filters with adjustable corner frequency and selectable order (2, 4 & 8; 12 dB/oct, 24 dB/oct & 48 dB/oct). |
| LPF & HPF Hardman | Low and high pass 4th and 8th order Hardman filters, unique to Linea Research. (These are steeper than Linkwitz/Riley filters – for the same order – and have some similarity to the Neville Thiele notched crossover filters; however they don’t perfectly sum to unity.) |
| Parametric | Parametric band push or cut filter with adjustable frequency, BW and gain. (2nd order) |
| Low Shelf, High Shelf | Low and high shelf filters with adjustable frequency, slope and gain. (2nd order) |
| 2nd All Pass | 2nd order all-pass filter with adjustable centre frequency and BW. |
Powersoft
Powersoft filters use Q and ignore the Preferences dialog, Global Preferences and Filter definition setting.
| Peaking | Parametric band push or cut filter with adjustable frequency, Q and gain. (2nd order) |
| Low Shelf, High Shelf | Low and high shelf filters with adjustable frequency, Q and gain. (2nd order) |
| LPF Bessel, HPF Bessel | Low and high pass Bessel filters with adjustable corner frequency and order (1 to 8; 6 dB/oct to 48 dB/oct).
Note: These Bessel filters are -3 dB at the selected frequency (unlike textbook Bessel filters whose gain at the selected frequency varies with order). |
| LPF Butter, HPF Butter | Low and high pass Butterworth filters with adjustable corner frequency and order (1 to 8; 6 dB/oct to 48 dB/oct). |
| LPF LR, HPF LR | Low and high pass Linkwitz/Riley filters with adjustable corner frequency and order (2, 4, 6 & 8; 12 dB/oct, 24 dB/oct, 36 dB/oct & 48 dB/oct) |
| All Pass | 2nd order all-pass filter with adjustable centre frequency and Q. |
QSC Q-SYS
QSC Q-SYS filters ignore the Preferences dialog, Global Preferences and Filter definition setting and use either BW or Q to match their use in Q-SYS.
| Parametric | Parametric band push or cut filter with adjustable frequency, BW/Q and gain. (2nd order) |
| Band-Pass | Band-pass filter with adjustable frequency, BW and bulk gain. (2nd order) |
| Band-Stop | Band-stop filters with adjustable frequency, BW and gain. (2nd order) |
| Notch | Notch filter with adjustable frequency and BW settings. (2nd order) |
| Low Shelf, High Shelf | Low and high shelf filters with adjustable frequency, BW/Q and gain. (2nd order)
Also has a bulk Master gain setting. |
| Dual Shelf | Shelf filter with adjustable frequency, BW/Q, low freq gain and high freq gain.
Also has a bulk Master gain setting. |
| LPF VarQ, HPF VarQ | Low and high pass 2nd order with adjustable corner frequency, Q and bulk gain. |
| LPF Be -3dB, HPF Be -3dB | Low and high pass Bessel filters with adjustable corner frequency, bulk gain and order (1, 2, 3 and 4; 6 dB/oct, 12 dB/oct, 18 dB/oct and 24 dB/oct).
Note: These Bessel filters are -3 dB at the selected frequency (unlike textbook Bessel filters with a gain at the selected frequency that varies with order). |
| LPF Be Nat, HPF Be Nat | Low and high pass Bessel filters with adjustable corner frequency, bulk gain and order (1, 2, 3 and 4; 6 dB/oct, 12 dB/oct, 18 dB/oct and 24 dB/oct).
Note: These Bessel filters are textbook filters with a level, at the selected frequency, that varies with order. |
| LPF Butter, HPF Butter | Low and high pass Butterworth filters with adjustable corner frequency, bulk gain and order (1, 2, 3 and 4; 6 dB/oct, 12 dB/oct, 18 dB/oct to 24 dB/oct). |
| LPF LR, HPF LR | Low and high pass Linkwitz/Riley filters with adjustable corner frequency, bulk gain and order (2 & 4; 12 dB/oct & 24 dB/oct). |
| LPF Cheb1, HPF Cheb1 | Low and high pass Chebshev Type 1 filters with adjustable corner frequency, bulk gain and order (1 to 4; 6 dB/oct to 24 dB/oct)
Note: Passband ripple is fixed at 0.33 dB. |
| AllPass | 2nd order all-pass filter with adjustable centre frequency and BW/Q |
Symetrix
To switch between BW and Q, go to the Preferences dialog, Global Preferences and Filter definition.
| FLX Parametric | FLEX parametric band push or cut filter with adjustable frequency, BW/Q and gain. (2nd order) |
| FLX Bandpass | FLEX bandpass filter with adjustable frequency, BW/Q and bulk gain. (2nd order) |
| FLX Notch | FLEX notch filter with adjustable frequency, BW/Q and bulk gain. (2nd order) |
| FLX Low Shelf, FLX High Shelf | FLEX low and high shelf filters with adjustable frequency, BW/Q and gain. (2nd order) |
| FLX LPF 12dB, FLX HPF 12dB | FLEX low and high pass 2nd order with adjustable corner frequency, BW/Q and bulk gain. |
| FLX LPF 6dB, FLX HPF 6dB | FLEX 1st order low and high pass filters, equivalent to Butterworth 1st order filters, with adjustable corner frequency. |
| LPF Bessel, HPF Bessel | Low and high pass Bessel filters with adjustable corner frequency, bulk gain and order (1 to 8; 6 dB/oct to 48 dB/oct) settings.
Note: These Bessel filters are always -3 dB at the selected frequency (unlike textbook Bessel filters with a gain at the selected frequency that varies with order). |
| LPF Butter, HPF Butter | Low and high pass Butterworth filters with adjustable corner frequency, bulk gain and order (1 to 8; 6 dB/oct to 48 dB/oct). |
| LPF LR, HPF LR | Low and high pass Linkwitz/Riley filters with adjustable corner frequency, bulk gain and order (2, 4, 6 & 8; 12, 24, 36 & 48 dB/oct). |
| AllPass | All-pass filters with adjustable centre frequency, order (1 or 2) and BW/Q (for 2nd order). |
| CD Horn | High shelf filter with adjustable frequency and gain. (2nd order)
Note: Positive gain only. |