Re: Drawing an EQ curve
Re: Drawing an EQ curve
- Subject: Re: Drawing an EQ curve
- From: email@hidden
- Date: Thu, 4 Sep 2003 14:34:30 -0400
I'd be surprised if, for example, Emagic went through the trouble of
doing FFTs etc. for an EQ curve display. Look at the display for their
"Fat EQ" (a multiband parametric / shelving EQ): I'd be surprised if
that was really accurate. I'll bet they did something much cheesier.
Let's say you have a parametric EQ that can act as a bandpass or a
notch. Start with two points, one on either side of the graph. Put
another point in between them. Make the X position proportional to the
ceter frequency, and the Y proportional to the gain in dB. Then do a
simple curve-fit between the endpoints and the middle point. A plot of
a 3rd-order polynomial should do the trick -- or a Bezier curve with
properly chosen control points. A bit of experimentation with a drawing
program would show what looks right. Of course, this idea is easily
extended to shelving, multiband, etc. (I'm a bit surprised that nobody
suggested this already - but probably you guys have more pride than I do
:) )
My feeling is that EQ displays are considered eye candy most of the
time. Nevertheless, it would be really cool to have a display that
reflects the real response of the function - I really like the FFT
suggestions, in principle. I'd imagine that it would take some extra
effort to get them to look pretty though. I'm thinking curve-fitting is
called for there. People expect the curves to look smooth, and I doubt
that an empirical approach would come out smooth-looking.
There is one problem with gain vs. frequency plots: I think they can be
a bit misleading. It's easy to forget that they are multiplicative; I
often catch myself looking at a frequency response curve and imagining
that it describes a frequency envelope applied to a signal; and of
course that isn't right. But that doesn't mean that an EQ curve isn't
useful.
---
Michael Ashton <email@hidden>
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