FIR Designer M : Channels – FIR Magnitude Adjust
This view is the first of five views used to create the channel FIR filter. Responses from all five views are combined or “convolved” into a single FIR filter which is then truncated and windowed on the channel Export tab.
Common magnitude prototype filters – see list below – can be used to shape the loudspeaker response and bring it closer to the target response. Each individual filter prototype can be set to minimum, linear or maximum phase. Note that minimum and maximum filters inherently impart a phase change. (The number of filter prototypes is unlimited.)
The blue line in the upper plot shows the loudspeaker magnitude response – after filtering from preceding tabs – subtracted from the channel target magnitude response.
The aim is to use filter prototypes to match the green line – the filtering for this tab – to the blue line. When closely matched, the loudspeaker response – after filtering – will be closer to the channel target.
Magnitude Adjusted Response
This plot shows the magnitude and phase for all preceding tabs up to, and including, the Magnitude Adjust, applied to every channel, and the combined system response. The channel target response is also shown.
Magnitude Filter Prototypes
BPass | Parametric band push or cut filter with adjustable frequency, BW/Q and dB settings. (2nd order) |
LShelf, HShelf | Low and high shelf filters with adjustable frequency, BW/Q and dB settings. (2nd order) |
LPF Be, HPF Be | Low and high pass Bessel filters with adjustable corner frequency and order (1 to 8; 6 dB/oct to 48 dB/oct) |
LPF Bu, HPF Bu | Low and high pass Butterworth filters with adjustable corner frequency and order (1 to 8; 6 dB/oct to 48 dB/oct) |
LPF Ch1, HPF Ch1 | Low and high pass Chebshev Type 1 filters with adjustable corner frequency, dB passband ripple and order (1 to 8; 6 dB/oct to 48 dB/oct) |
LPF Ch2, HPF Ch2 | Low and high pass Chebshev Type 2 filters with adjustable corner frequency, dB stopband attenuation and order (1 to 8; 6 dB/oct to 48 dB/oct) |
LPF Ellip, HPF Ellip | Low and high pass Ellyptic filters with adjustable corner frequency, dB passband ripple, dB stopband attenuation 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, dB sidelobe attenuation and order (4,6 & 8; 24dB/oct, 36 dB/oct & 48 dB/oct) |
LPF BW, HPF BW | Low and high pass linear-phase brick-wall crossover filters with adjustable corner frequency and time length (in millseconds) |