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Questions tagged [biquad]

Biquad is referred to either analog or digital second order filters

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First order filters in Direct Form I (RBJ Cookbook)

I've implemented second order biquad filters using the famous RBJ Cookbook. I also want to implement first order lowpass and highpass filters. I was hoping to use the same code, so I need to define ...
MysteryPancake's user avatar
5 votes
1 answer
195 views

"Tone Control" IIR filter coefficients

The documentation for Analog Device's sigmastudio shows some of the formulas behind their biquad IIR filter coefficients. The usual suspects (HP, LP, peaking, ...) as described in RBJ's cookbook are ...
playduck's user avatar
3 votes
1 answer
134 views

Audio EQ Cookbook Stability

I'm implementing 6 cascaded biquad peaking filters to make a 6-band EQ. In the system I want to calculate the coefficients on the fly (it's just gain thats changing, center frequency and BW aren't). I ...
Michael Beckwith's user avatar
2 votes
1 answer
99 views

low shelving filter frequency response diagnosis

I am building a second order modified biquad filter based on an implementation by Will Pirkle in "designing audio effect plugins in c++". However when I look at my implementation's ...
Brian Barry's user avatar
1 vote
1 answer
72 views

How to specify the cut-off frequence in cascaded biquad filters?

As part of my effort to understand how a high-pass filter can be implemented, I'm reading this section of HandWiki. My question here is: How do the 2 simple formula presented there filter out at a cut-...
DannyNiu's user avatar
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1 answer
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Understanding how to implement high-pass filter with cascaded biquad filters

I'm trying to understand how to implement a high-pass filter using, quote: a cascasded biquad direct form II IIR filter with a cut-off of 8kHz. DSP is a complete new field for me, and the ...
DannyNiu's user avatar
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2 votes
0 answers
61 views

How do I obtain narrowband reverberation times in the bass range to detect room modes?

I calculate my impulse response according to this principle. Calculating the inverse filter for the (exponential) sine sweep Method. With the obtained impulse response I calculate my reverberation ...
Hannes Broschk's user avatar
1 vote
1 answer
102 views

How to match coefficients of a SVF compared to Biquad in order to Plot the frequency response?

I'd like to output the frequency response of this filter. Here's how the coefficients are calculated: ...
markzzz's user avatar
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1 vote
0 answers
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Is it possible to lower the slope of a biquad lowpass? [duplicate]

I'd like to implement a lowpass with arbitrary slope. I'm currently cascading biquads in order to get a higher order, hence higher slope. But is it possible to do the opposite - lower the slope of one ...
Vojtěch Melda Meluzín's user avatar
1 vote
1 answer
231 views

using scipy.signal.sosfilt to filter a stereo signal with zi, zf

I'm stuck trying to filter a two-channel signal using sosfilt() with the zi initial state. I need to use the zi parameter so I can carry the filter state over ...
fearless_fool's user avatar
0 votes
1 answer
185 views

design of cascaded biquad filter

I have to compare the response of an 8th order IIR filter and its equivalent 4 stage cascaded biquad structure. A sinusoidal signal is given as input to both the systems and the output responses are ...
Aami's user avatar
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1 answer
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BPF design as cascaded second order biquads

I am trying to design a bandpass filter in MATLAB with following specs: $$\texttt{f_s = 20000Hz}$$ $$\texttt{3dB freq = [392 464]Hz}$$ $$\texttt{filter order = 8}$$ When I tried to implement the ...
Aami's user avatar
  • 315
6 votes
1 answer
306 views

Pole Quantization Patterns in 2nd Order IIR Resonators

Background My typical approach to fixed point design for digital filters is to iteratively scale and increase quantization while comparing the fixed point simulation to the floating point design ...
Dan Boschen's user avatar
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2 votes
3 answers
466 views

Series vs Parallel Biquad Filters

What are the pros and cons of arranging a set of biquad filters in series and parallel? I gather that series should be used in cases where the filters contribute to the same passbands and vice versa ...
cberk1's user avatar
  • 111
1 vote
1 answer
489 views

How to calculate IIR Lattice Filter Coefficients for Biquad Filter

If I have a biquad filter with known $a_1, a_2, b_0, b_1, b_2$ coefficients, how do I calculate the corresponding lattice/ladder coefficients? I have found information on deriving the lattice ...
cberk1's user avatar
  • 111
2 votes
2 answers
186 views

What procedure to find the parameters of a given filter prototype to fit a desired frequency response?

To model the frequency response of a system, I am looking for a method to fit the response of cascaded bi-quad filters to the response of that system using an optimization algorithm. The $S$-domain ...
papaya's user avatar
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2 votes
2 answers
2k views

How to implement cascaded biquad transfer functions in Python/SciPy

I am trying to implement in python/Scipy the biquad filter with the following S-domain transfer function: $$ H(s)=\frac{w_0^{2N-1}(s+w_z)}{[s^2+(w_0/Q)s+w_0^2]^N} $$ My problem here is that because of ...
papaya's user avatar
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0 answers
300 views

Discrepancy in frequency response of biquad filter (in Python)

I have written a simple biquad filter class but when I check its frequency response, I get different results with different methods. If I check it "empirically" (by taking the FFT of its ...
Zimzel Zamzel's user avatar
2 votes
2 answers
304 views

What is the $Q$ of successive Second-Order Sections of an $N$th-order Butterworth low-pass filter?

What if you had an $N$th-order Butterworth lowpass filter filter with -3 dB frequency of $\Omega_0$? $$ \Big| H(j\Omega) \Big|^2 = \frac{1}{1 + \left(\frac{\Omega}{\Omega_0}\right)^{2N}} $$ The number ...
robert bristow-johnson's user avatar
3 votes
3 answers
668 views

ELI5: How do biquad filters like bandpass "know" the frequency of a signal?

I understand the code behind biquads, but I fail to understand how 5 coefficients in a biquadratic formula can isolate frequencies so precisely, especially considering it only takes the last two ...
Martmists's user avatar
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1 vote
0 answers
149 views

High pass biquad cascade transposed direct form II low frequency accuracy

I'm quite new to DSP and I'm trying to implement high pass biquad cascade in transposed direct form II. Currently my implementation has very poor accuracy at cutoff frequencies that are less than 5kHz ...
minimalistic's user avatar
2 votes
1 answer
614 views

How to optimally normalize filter coefficients?

I have designed an IIR filter in Matlab that comprises the following biquads ...
neolith's user avatar
  • 147
0 votes
1 answer
102 views

Derive Time-Domain Biquad Coefficients from Z-Domain

I'm trying to derive the time-domain coefficients of a biquad filter based on its z-domain coefficients. The purpose is to import externally-generated EQ filters (in z-domain) into Max/MSP (in time-...
Joel's user avatar
  • 55
1 vote
3 answers
573 views

Biquad cascading frequency response

I am implementing EQ lines in my filter. I need to do biquad with slope 24 db/oct, 36/oct and bigger so I would like to cascade several biquads. I am stuck with calculating frequency response of two ...
mike89's user avatar
  • 11
0 votes
1 answer
409 views

Direct form 1 filter equation for a biquad filter

In general, we all know that the direct form 1 equation for a biquad filter is given by $$y(n) = b_0x(n) + b_1x(n-1) + b_2x(n-2) - a_1y(n-1) - a_2y(n-2)$$ But when it comes to practical applications ...
rkc's user avatar
  • 59
1 vote
2 answers
775 views

Converting cascaded biquads to parallel biquads

I need to convert a fourth-order IIR filter made using two cascaded second-order sections with the transfer function: $$ H(z) = \frac{b2_{1}z^{-2} + b1_{1}z^{-1} + b0_{1}}{a2_{1}z^{-2} + a1_{1}z^{-1} ...
Nizar Nizar's user avatar
0 votes
2 answers
1k views

Calculating the true values of biquad filter coefficients from normalized form

I have a C code in which the IIR filter(BiQuad) uses only 4 (normalized) coefficients per stage (a2/a0,a1/a0,b2/b0,b1/b0) instead of 6 coefficients (a0,a1,a2,b0,b1,b2). I know that the value of a0 is ...
rkc's user avatar
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0 votes
2 answers
139 views

IIR Cascaded Filter Response, Unexpected Results

I am attempting to understand how to manipulate portions of a cascaded series of biquad notch filters in a control system I am working with. As part of determining the composite response of all the ...
Maximum_Entropy's user avatar
1 vote
3 answers
1k views

How do you calculate the group delay in samples of a Biquad Filter at a given frequency from the coefficients?

If I have a BiQuad all-pass filter with a given set of coefficients such as: g: 0.903228 a1: -1.88142 a2: 0.903228 B1: -2.08299 B2: 1.10714 And my operation per ...
mike's user avatar
  • 533
0 votes
1 answer
601 views

Biquad high-pass filter not working as expected

I'm trying to implement a high-pass filter using the the coefficients described in RBJ's well-known EQ cookbook (see https://www.w3.org/TR/audio-eq-cookbook/). However, when I run white noise through ...
user44928's user avatar
1 vote
1 answer
99 views

bibliography about implementation of IIR filters

I need to implement a 6th order IIR filter. The filter I need to implement is the A-weighting. I've simply used the bilinear function of Matlab with an fs of 20Khz. I need to implement this over the ...
Gaston's user avatar
  • 21
0 votes
1 answer
108 views

Biquad Filter Non-Linearity

I'm using a biquad filter algorithm in my project. I got 3, 16 size variable arrays summing into one and then gets filtered. Now i want to filter each array seperately and sum after that, which if the ...
Can Uysal's user avatar
0 votes
0 answers
177 views

Biquad Type-II Coefficient Generation

I have a Biquad II filter implementation in my embedded environment and I'm trying to find some equations to generate the coefficients for it. I have already found the Audio Eq Cookbook, which simply ...
Can Uysal's user avatar
0 votes
1 answer
284 views

Why does my low pass filter diverge below 7000 Hz?

I'm trying to create a LPF, using language JAVA. My first aim is to understand how filters design is working and the second one is to create a "home made" equalizer with "home made" filters. To help ...
Dr_Click's user avatar
  • 161
0 votes
1 answer
137 views

Known problems with IIR DF2 when using 64-bit floating point processing?

So far I was using DF1 for biquad filters for audio DSP, but it turns out that it is possible to gain significant performance gains using the new AVX/AVX512 instruction sets using DF2. Are there any ...
Vojtěch Melda Meluzín's user avatar
2 votes
1 answer
294 views

Biquad and polarity flipping

Assuming normalized biquad coefficients: $$ H(z) = \frac{b_0 + b_1z^{-1} + b_2z^{-2}} {1 + a_1z^{-1} + a_2z^{-2}} $$ And taking the definition of flipping the polarity as multiplying every tap in a ...
keith's user avatar
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1 vote
0 answers
253 views

Issue with the Massberg Analog-Matched Low Pass Filter

Implemented the filter mentioned in title using Octave and couple sources Vicanek and Zeitlin (LPF.cpp). Got filter working otherwise but, ... when tested the responses against 'analog model' of the ...
Juha P's user avatar
  • 917
2 votes
1 answer
795 views

How would I calculate the state-variables of digital biquad filter (direct form II transposed) at steady-state?

I'm attempting to calculate the steady-state state variables for a digital biquad filter direct form II (transposed). Illustration For example, let assume the filter is fed a constant input of ...
Izzo's user avatar
  • 882
1 vote
2 answers
1k views

Help with audio EQ cookbook BPF filters and Q

I am fairly new DSP, and am using maths that I have not used in 20-30 years. I have been working with Cookbook formulae for audio EQ biquad filter coefficients by Robert Bristow-Johnson and am having ...
mw.'s user avatar
  • 113
3 votes
1 answer
394 views

Can a Goertzel filter response be mapped to a Direct Form II Biquad IIR Filter

I am looking at the structure of the Goertzel Filter, and it seems like I can map its coefficients to the standard implementation of the CMSIS DSP Biquad Cascade IIR Filter. Is this possible or should ...
Luke Gary's user avatar
  • 133
1 vote
2 answers
94 views

MATLAB's $\tt dsp.ParametricEQFilter$ bandwidth question

Consider the following code: ...
CyDe's user avatar
  • 23
0 votes
1 answer
239 views

Biquad Treble Shelf filter gain being weird

Trying to compute Biquad Coefficients for use in a codec chip TLV320AIC3100. Bass Shelf(boost and attenuation) work as expected. Treble Shelf attenuation works as expected but Treble Shelf boost is ...
John O's user avatar
  • 1
1 vote
1 answer
515 views

Is it possible to combine two or more Biquads?

I've wrote a Equalizer, and now it apply the Biquads in serie (cascade), I was just thinking if i can combine the biquads it will more efficient than applying one-per-one. Is that possible?
Victor Aurélio's user avatar
3 votes
4 answers
2k views

Avoiding clicks with changing biquad coefficients

I have a DSP application that filters a signal with five cascaded biquads whose coefficients are determined by the Audio EQ Cookbook formulae (Thanks for this work, Mr. Bristow-Johnson btw). Each ...
UnbescholtenerBuerger's user avatar
0 votes
0 answers
126 views

PeakEq center frequency does not match frequency response

Following the Cookbook i calculed these coefficients: ...
Victor Aurélio's user avatar
1 vote
1 answer
1k views

How do scaling of the coefficients for the poles of a biquad filter affect the gain?

Given a digital filter consisting of a chain of digital biquad filters. Given a digital biquad filter with a normalized Direct form 1 difference equation: $ y_n = b_0x_n + b_1x_{n-1}+b_2x_{n-2} - ...
Baard's user avatar
  • 113
0 votes
0 answers
449 views

Software implementation recipe of cascaded Biquad IIR filter

I have been given the task of measuring the performance of Biquad IIR filters on a new CPU that we are evaluating. What I know is that the Biquad filters can be cascaded to form higher order filters. ...
Raj's user avatar
  • 279
2 votes
3 answers
779 views

IIR biquad real-time filter just output noises

I've implemented a IIR filter but it outputs only noise (like FM radio out of tuning) and I can't see what's wrong. This is the processing function: ...
Victor Aurélio's user avatar
1 vote
1 answer
1k views

Biquad filter from Matlab to C using "tf2sos"

This is a biquad implementation I use: ...
Danijel's user avatar
  • 492
2 votes
1 answer
1k views

4th order high-pass filter on a DSP: standard or biquads?

I have two C implementations of 4th order high-pass filter (fs = 16 kHz, cut-off=100 Hz, designed using Matlab ...
Danijel's user avatar
  • 492