filtRespLR

Frequency response (transfer function) of an nth-order Linkwitz-Riley filter

Computes the complex frequency response function (transfer function) of an even-order low-pass, high-pass or all-pass Linkwitz-Riley filter.

Syntax

h = filtRespLR(f,n,fc,filtType)
h = filtRespLR(f,n,fc)
filtRespLR(__)
filtRespLR()

Description

h = filtRespLR(f,n,fc,filtType) returns the frequency response (transfer function) column vector computed at the frequencies supplied in f (in Hz). Here n must be even, and is the order of the Linkwitz-Riley filter, fc is the –6.02 dB cutoff frequency, and filtType is used to specify whether the filter is a lowpass, highpass or allpass filter type.

Note that the values of n and/or fc can be specified as scalars or as vectors. If only one of the two is a vector, a matrix of column vectors is returned. If both n and and fc are vectors, e.g., n = [2, 4] and fc = [500, 1000, 1500], then a three-dimensional array of column vectors is returned. In this case, the second dimension corresponds to each n(j), j=1:numel(n), while the third dimension corresponds to each fc(k), k=1:numel(fc).

A highpass filter is specified by setting filtType to be one of the following: 'H', 'HP', 'HIGHPASS', 'HIGH-PASS'.

A lowpass filter is specified by setting filtType to be one of the following: 'L', 'LP', 'LOWPASS', 'LOW-PASS'.

An allpass filter is specified by setting filtType to be one of the following: 'A', 'AP', 'ALLPASS', 'ALL-PASS'. These are "recombining to allpass" filters, comprised of the relevant even-order Linkwitz-Riley filters. The appropriate sign change is applied to the highpass section when n = 2, 6, etc.

If filtType is omitted or is empty ([]), then a highpass filter is the default choice.

filtRespLR(__) with no output arguments plots the magnitude and phase response of the Linkwitz-Riley filter (its frequency response).

filtRespLR() with no input arguments plots the magnitude and phase response of a number of example Linkwitz-Riley filters.

References

Linkwitz, Siegfried H. (1976). Active Crossover Networks for Noncoincident Drivers. Journal of the Audio Engineering Society, Volume 24, Number 1, pages 2–8. http://www.aes.org/e-lib/browse.cfm?elib=2649

Siegfried H. Linkwitz (1976). Active Crossover Networks for Noncoincident Drivers". Linkwitz Lab. https://www.linkwitzlab.com/JAES/jaes_papers76.htm