Category Archives: Biquads

Biquad calculator v3

Posted on September 2, 2021 by Nigel Redmon

The latest version of the biquad calculator. It also takes on the functionality of the frequency response grapher:

Posted in Biquads, Digital Audio, Filters, Widgets | Tagged | 56 Comments

About coefficient conventions

Posted on January 4, 2017 by Nigel Redmon

It’s been asked many times, so it’s worth an article explaining the conventions used on this site for transfer functions, and why they may differ from what you see elsewhere. People run into this most often with biquads: I use … Continue reading →

Posted in Biquads, IIR Filters | 7 Comments

Filter frequency response grapher

Posted on December 8, 2016 by Nigel Redmon

Here’s a tool that plots frequency response from filter coefficients. Hz linearlog 10log 2 Plot auto40 dB30 dB20 dB10 dB0 dB-10 dB-20 dB-30 dB-40 dB Max 60 dB80 dB100 dB120 dB140 dB160 dB180 dB Range a coefficients (zeros) b coefficients … Continue reading →

Posted in Biquads, Filters, FIR Filters, IIR Filters, Widgets | 15 Comments

Evaluating filter frequency response

Posted on December 1, 2016 by Nigel Redmon

A question that pops up for many DSP-ers working with IIR and FIR filters, I think, is how to look at a filter’s frequency and phase response. For many, maybe they’ve calculated filter coefficients with something like the biquad calculator … Continue reading →

Posted in Biquads, FFT, Filters, FIR Filters, IIR Filters | 27 Comments

Cascading filters

Posted on September 29, 2016 by Nigel Redmon

Sometimes we’d like to cascade biquads to get a higher filter order. This calculator gives the Q values for each filter to achieve Butterworth response for lowpass and highpass filters. Order: 234567891011121314151617181920 Q values: You can calculate coefficients for all biquad … Continue reading →

Posted in Biquads, Filters, IIR Filters, Widgets | 40 Comments

Pole-Zero placement v2

Posted on October 28, 2013 by Nigel Redmon

Pair Pole mag Pole angle Pair Zero mag Zero angle Sample rate (Hz) linearlog Plot A new pole-zero calculator An JavaScript remake of the old Java-based pole-zero placement applet—visit that page for tips on pole-zero locations for standard biquads. The … Continue reading →

Posted in Biquads, Digital Audio, Filters, IIR Filters, Widgets | 15 Comments

Biquad calculator v2

Posted on October 13, 2013 by Nigel Redmon

Type:lowpasshighpassbandpassnotchpeaklow shelfhigh shelfone-pole lpone-pole hp Plot:linearlog Sample rate (Hz) Fc (Hz) Q Gain (dB) Here’s an update of the biquad calculator. It adds one-pole highpass and lowpass filters, and frequency, Q, and gain sliders. The sliders cover the range of … Continue reading →

Posted in Biquads, Digital Audio, Filters, IIR Filters, Widgets | 96 Comments

Biquad C++ source code

Posted on November 26, 2012 by Nigel Redmon

I don’t want to get into the business of teaching people how to code—there are a huge number of free resources available on the internet to that do that. But I’ll give a small taste for those trying to get … Continue reading →

Posted in Biquads, Digital Audio, Filters, IIR Filters, Source Code | 96 Comments

Biquad formulas

Posted on January 2, 2011 by Nigel Redmon

For fixed filters, we can plug biquad coefficients into our programs. But often, we need to calculate them on the fly, to user settings or changes in sample rate. As a companion to the biquad calculator, here are the formulas … Continue reading →

Posted in Biquads, Digital Audio, Filters, IIR Filters | 48 Comments

A biquad calculator

Posted on December 20, 2010 by Nigel Redmon

Something useful: a biquad filter coefficient calculator… Continue reading →

Posted in Biquads, Digital Audio, Filters, IIR Filters, Widgets | 37 Comments