
Exponential curve for
Type : Exponential curve References : Posted by neolit123 [at] gmail [dot] com
Notes : When you design a frequency control for your filters you may need an exponential curve to give the lower frequencies more resolution.
F=2020000hz
x=0100%
Case (control middle point):
x=50%
F=1135hz
Ploted diagram with 5 points:
http://img151.imageshack.us/img151/9938/expplotur3.jpg
Code : //tweak  14.15005 to change middle point and F(max)
F = 19+floor(pow(4,x/14.15005))+x*20;

Comments
Added on : 30/10/08 by neolit123[ AT ]gmail[ DOT ]com Comment : same function with the more friendly exp(x)
y = 19+floor(exp(x/10.2071))+x*20;
middle point (x=50) is still at 1135hz
Added on : 30/10/08 by neolit123[ AT ]gmail[ DOT ]com Comment : Here is another function:
This one is much more expensive but should sound more linear.
//t  offset
//x  0100%
//y  2020000hz
t = 64.925;
y = floor(exp(x*log(1.059))*t  t/1.45);
Comparison between the two:
[IMG]http://img528.imageshack.us/img528/641/plot1nu1.jpg[/IMG]
Added on : 01/11/08 by neolit123[ AT ]gmail[ DOT ]com Comment : Yet another one! :)
This is one should be the most linear one out of the 3. The 50% appears to be exactly the same as Voxengo span midpoint.
//x  0100%
//y  2020k
y = floor(exp((16+x*1.20103)*log(1.059))*8.17742);
//x=0, y=20
//x=50, y=639
//x=100, y=20000

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