{"id":79,"date":"2010-12-20T19:14:50","date_gmt":"2010-12-21T03:14:50","guid":{"rendered":"http:\/\/www.earlevel.com\/main\/?p=79"},"modified":"2021-12-28T23:09:53","modified_gmt":"2021-12-29T07:09:53","slug":"biquad-calculator","status":"publish","type":"post","link":"https:\/\/www.earlevel.com\/main\/2010\/12\/20\/biquad-calculator\/","title":{"rendered":"A biquad calculator"},"content":{"rendered":"<div id=\"container1-20101220\" style=\"width: 600px; height: 200px;\"><\/div>\n<form name=\"biquad_params\">\n<table style=\"background-color: #ffffff; border: 0; margin: 0; width: 600px;\">\n<tbody>\n<tr>\n<td style=\"vertical-align: top;\">Type:<select name=\"Type\" onchange=\"drawIt_biquad()\"><option value=\"lowpass\">lowpass<\/option><option value=\"highpass\">highpass<\/option><option value=\"bandpass\">bandpass<\/option><option value=\"notch\">notch<\/option><option value=\"peak\">peak<\/option><option value=\"lowShelf\">low shelf<\/option><option value=\"highShelf\">high shelf<\/option><\/select><\/td>\n<td style=\"vertical-align: top;\">Plot:<select name=\"PlotType\" onchange=\"drawIt_biquad()\"><option value=\"linear\">linear<\/option><option value=\"log\">log<\/option><\/select><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/form>\n<table style=\"background-color: #ffffff; border: 0; margin: 0; width: 600px;\">\n<tbody>\n<tr>\n<td style=\"vertical-align: top; border: 0;\">\n<div><input id=\"biquad_Fs\" style=\"text-align: right; width: 4em; margin: 0 6px 6px 0;\" name=\"Fs\" type=\"text\" value=\"44100\" \/>Sample rate (Hz)<\/div>\n<div><input id=\"biquad_Fc\" style=\"text-align: right; width: 4em; margin: 0 6px 6px 0;\" name=\"Fc\" type=\"text\" value=\"10000\" \/>Fc (Hz)<\/div>\n<div><input id=\"biquad_Q\" style=\"text-align: right; width: 4em; margin: 0 6px 6px 0;\" name=\"Q\" type=\"text\" value=\"0.7071\" \/>Q<\/div>\n<div><input id=\"biquad_Gain\" style=\"text-align: right; width: 4em; margin: 0 6px 6px 0;\" name=\"Gain\" type=\"text\" value=\"6.0\" \/>Gain (dB)<\/div>\n<\/td>\n<td style=\"vertical-align: bottom; border: 0;\"><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><script type=\"text\/javascript\" src=\"\/scripts\/utils\/flotr2.min.js\"><\/script><script type=\"text\/javascript\" src=\"\/scripts\/widgets\/20101220\/biquads.js\"><\/script><\/p>\n<p>Something useful: a biquad filter coefficient calculator. Set the filter <em>Type<\/em>, the <em>Sample rate<\/em> (or 1.0 for &#8220;normalized&#8221; frequency), and cutoff of center frequency <em>Fc<\/em>. You can adjust <em>Q<\/em> for lowpass, highpass, bandpass, notch, and peak filters (use 0.7071&#8211;which is 1 divided by the square root of 2&#8211;for Butterworth lowpass and highpass), and <em>Gain<\/em> for peak and shelving filters. View the frequency response with a linear or log scale. You can copy and past the resulting coefficients into your programs.<\/p>\n<p>More info on biquads in previous posts, <a href=\"\/main\/2003\/02\/28\/biquads\">here<\/a> and <a href=\"\/main\/2003\/03\/02\/the-bilinear-z-transform\">here<\/a>.<\/p>\n<p><del><em>Note that there is an improved version of this calculator <a href=\"\/main\/2013\/10\/13\/biquad-calculator-v2\/\">here<\/a>.<\/em><\/del><\/p>\n<p><em>There is an even more improved version <a href=\"\/main\/2021\/09\/02\/biquad-calculator-v3\">here<\/a>.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Something useful: a biquad filter coefficient calculator&#8230; <a href=\"https:\/\/www.earlevel.com\/main\/2010\/12\/20\/biquad-calculator\/\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[21,4,8,9,30],"tags":[],"_links":{"self":[{"href":"https:\/\/www.earlevel.com\/main\/wp-json\/wp\/v2\/posts\/79"}],"collection":[{"href":"https:\/\/www.earlevel.com\/main\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.earlevel.com\/main\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.earlevel.com\/main\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.earlevel.com\/main\/wp-json\/wp\/v2\/comments?post=79"}],"version-history":[{"count":3,"href":"https:\/\/www.earlevel.com\/main\/wp-json\/wp\/v2\/posts\/79\/revisions"}],"predecessor-version":[{"id":1314,"href":"https:\/\/www.earlevel.com\/main\/wp-json\/wp\/v2\/posts\/79\/revisions\/1314"}],"wp:attachment":[{"href":"https:\/\/www.earlevel.com\/main\/wp-json\/wp\/v2\/media?parent=79"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.earlevel.com\/main\/wp-json\/wp\/v2\/categories?post=79"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.earlevel.com\/main\/wp-json\/wp\/v2\/tags?post=79"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}