
Plotting R BJ Equalisers in Excel
References : Posted by Web Surf Linked file : rbj_eq.xls
Notes : Interactive XL sheet that shows frequency response of the R BK high pass/low pass, Peaking and Shelf filters
Useful if 
You want to validate your implementation against mine
You want to convert given Biquad coefficients into Fo/Q/dBgain by visual curve fitting.
You want the Coefficients to implement a particular fixed filter
 Educational aid
Many thanks to R BJ for his personal support !!
Web Surf WebsurffATgmailDOTcom
Code : see attached file 
Comments
Added on : 14/04/06 by Paul_Sernine75[ AT ]hotmail[ DOT ]fr Comment : It also works perfectly with the openoffice2.02 suite :)
Added on : 24/07/07 by jackmattson att gmial Comment : Ok, so I'm about to make my first filter so I really have no idea about coefficients yet but damn this is the coolest .xls I've ever seen! And I see a bunch every day. :?
Added on : 13/09/07 by WebsurffATgmailDOTcom Comment : Thanks,
It's just an implementation of the R BJ cookbook formulae for parametric equalisers. RBJ personally assisted me while I was writing this XLS. The real Kudos goes out to him !!
I wrote this as in intermediate tool while I was writing some Guitar effect DSP routines.
One prob it has : If the Q is too sharp, the peak filters have a very sharp tip. It is possible then as you slide the F sliders, that the chosen F is not one of the data points that I am plotting.
The net result is that the peak of a hiQ filter seems to increase/decrease as you move F. This is a shortcoming of the way I programmed my XLS and is not a problem with the R BJ equations.
PS : I saw the same problem with other similar S/W on the net !!!
PS : Anyone know how to do curve fitting so that we enter in some points through which the frequency response must pass, and it generates best set of F,G,Q ?
Added on : 17/04/11 by WebsurffATgmailDOTcom Comment : Date: Sun, 17 Apr 2011 12:34:09
Subject: RBJ Filter Plotter Spreadsheet
From: Robert Bonini <XXXXXXXXXX@gmail.com>
To: websurff @ gmail . com
Just wanted to complement you on the good work. I came across your RBJ filter plotter spreadsheet, and it's quite good.
The version I have is dated Feb.2006, so this may have been addressed already but I did notice a small issue with the sample frequency input.
Anything other than 44.1 KHz would cause the response curves to peak at incorrect values on the x axis. The normalized frequency 'w' was
being referenced to 44100, and not to the Fs cell. I modified the formula to absolute reference B56 and it solved that problem.
Thanks for your great work,
robert

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