Re: Drawing an EQ curve
Re: Drawing an EQ curve
- Subject: Re: Drawing an EQ curve
- From: Herbie Robinson <email@hidden>
- Date: Fri, 5 Sep 2003 03:39:03 -0400
At 3:50 PM -0400 9/3/03, Robert Grant wrote:
Thanks for responding - but yeah I think you misunderstood me. I'm
trying to wrap Apple's EQ AUs in to a nice EQ effect for a mixer
channel. So I don't have access to the methods they're using to
calculate the curve, just the parameter values. (I should have
mentioned that in the first email :-))
But I know that when using a parametric EQ it's very useful to get a
visual of the curve. So...
I like the approach of doing an FFT on an offscreen copy of the
plugin, because...
I measured a lot of different filter plug-ins (in the TDM domain) and
I've found that there is no accepted definition of Q. On top of
that, the resulting bandwidth is dependent on the gain setting as
well as the Q setting (constant bandwidth filters) and this is not
the same from filter to filter. For example, if you run white noise
through filter A with a given Gain and Q setting and then set up
filter B for the same frequency response (using FFTs), the Q you end
up with for filter B will probably not be the same as for filter A.
In addition, if you increase the gain on both filters by 6dB, you
will probably have to adjust the Q on one of them to get the same
response.
The best way to do it would be to generate the response from the IIR
&/or FIR filter coefficients. If you can't do that (and don't do the
FFT trick), then what you display is not going to be accurate and,
IMO, inaccurate is worse than no display at all.
--
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