[LAU] jamin (was: Albums under a label recorded and/or mixed with Linux)

fons at kokkinizita.net fons at kokkinizita.net
Sun Oct 3 16:21:32 UTC 2010

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.



There are three of them, and Alleline.

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