3 Oct
2010
3 Oct
'10
6:21 p.m.
On Sun, Oct 03, 2010 at 12:31:59PM +0200, Philipp Überbacher wrote:
Afaik, -3dB == cutoff frequency, at least with those
passive electronic
single pole low/highpass filters.
They are second order, using biquads. With first order this problem
wouldn't exist as 1/(1+s) + s(1+s) = 1.
So If I understand that and read the
picture correctly, you refer to the frequency range between the cutoff
of the low-band and the lower cutoff of the mid-band, which is about
300Hz, as well as the upper cutoff of the mid-band and the cutoff of the
high-band, which looks even wider to me, about 400Hz.
What you see is not the shape of each filter, but how they combine.
The lowpass is of the form 1/(1 + d s + s^2), the higphass is
s^2/(1 + d s + s^2), s = j f / fxover, d > 0.
The nominator of the sum doesn't have any term in s, and the two
others cancel at the xover frequency where s = j. Hence gain is
zero at the xover frequency.
I also wonder a bit why the 3kHz dip is at 3.1kHz..
Just a small gain difference in the compressors. If you
bypass them the dip is at exactly the set frequency.
Ciao,
--
FA
There are three of them, and Alleline.