Rate at which it operates shown in brackets, and in the EQ Filters panel. The currently selected equaliser is shown in the panel title, with the sample Necessary to comply with the ranges and resolutions of the chosen equaliser. Filters alreadyĭefined are retained where possible, but parameter values will be adjusted if Changing the equaliser type updates the filter panel,Īpplying the settings appropriate to the selected equaliser. In MSO, the gain value A 0 and Q value Q m are chosen, and Q p and Q z are computed as follows.The Equaliser panel is used to select the type of equaliser whose responses Using this notation, we can write the transfer function H( s) of equation (1) above as follows. To see how it's used, I'll also introduce Q z, the "zero Q" as hinted in the quote above from the Hypex manual. This is the definition of Q that's used by the Multi-Sub Optimizer software (MSO), so I'll call it Q m, the "MSO Q". Thus the same filter with opposite gains will cancel." In the Hypex amplifier manual, the revised Q definition is described as follows. The revised definition for Q is given by equations 1 and 2 in the latter paper. One popular way of defining Q to obtain the symmetry mentioned above is described in the PDF manual of the Hypex PSC2.400 amplifier and a PDF whitepaper by THAT Corp. Modifying the Definition of Q for Symmetry The filter as defined above in equation (1) does not have this symmetry property. That is, if the former filter had a transfer function H 1( s) and the latter a transfer function H 2( s), we want H 2( s)=1/ H 1( s). ![]() Where ω 0 = 2π f 0 and the gain in dB at the center frequency is A 0(dB) = 20 * log 10( A 0).įrom the point of view of the user of such a PEQ, a desirable property would be that two filters having identical Q and center frequency, but one with a boost of "x" dB and another with a cut of "x" dB at the center frequency would combine to be perfectly flat. ![]() The transfer function H( s) of this PEQ filter in terms of Q p (the pole Q) can be written as: We'll look at a PEQ filter having a center frequency f 0 and a gain A 0 at the center frequency. The classical definition of Q (which RBJ calls the "EE Q") is sometimes called the "pole Q". The classical definition of Q will be discussed first. We'll discuss different conventions for defining Q, and their relationship to one another. His definition of Q is different from the classical definition found in electrical engineering texts. On his web page titled Cookbook formulae for audio EQ biquad filter coefficients, he introduces a new definition for the Q of PEQ filters (which he calls "peaking EQ" filters). However, there's only a brief mention of filter Q in that article. In that article, he derives a number of important results we'll look at shortly. The most important of these is a PDF article titled The Equivalence of Various Methods of Computing Biquad Coefficients for Audio Parametric Equalizers. To get the most of this article, you'll need to read two articles by RBJ. Robert Bristow-Johnson ("RBJ") has written the most thorough discussion I've read of the math related to the audio PEQ. One of the most useful types of electrical filters for audio equalization (EQ) is the parametric EQ (PEQ). ![]() Parametric Equalizer " Q" Definitions and Bandwidth Introduction Parametric Equalizer "Q" Definitions and Bandwidth
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