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Old 2005-04-26, 00:21
wouterschakel wouterschakel is offline
Join Date: Jun 2001
Posts: 0
Reason has a hidden high pass filter


This is quite a technical story, if you just want a HP Filter, just download the song (see link below).


I was trying to figure out how the stereo imager devided the sound in 2 seperate frequency bands. I figured it must be something like this:
- the original sound is put through a 12db Low Pass filter, beeing the low band.
- the low band signal is subtracted from the original, beeing the high band signal.
(Note, in this way 'low band' + 'high band' = 'original', this would not be the case when using a High Pass AND a Low Pass filter parallel)
Running sound through the stereo imager soloing the low band creates a signal very very very similar to a signal through the 12db LP filter (on the ECF-42 Filter). However, I couldn't test the same for the High Band because of the very old problem that Reason does not have a stand-alone HP Filter.

But then I realized...

Running a sound through the stereo imager, having both stereo knobs at no activity, turning the X-over knob like hell... does not have ANY effect. Meaning that 'low band' + 'high band' is indeed very accuratly the 'original' sound. Otherwise a slight notch or bandpass effect should happen at the X-over frequency.

Now I know, from creating my own stereo imager in NI Reaktor, that the 'HP + LP deviding method' does produce a signal that doesn't differ alot from the original, let's say about 90% the same.

In short:
- the low band of the stereo imager is 99% like the 12db LP Filter.
- '12db high band filter' + '12db low band filter' = 90% like the original.
- 'original' minus 'low band' is 'high band'

Take these three together leads to the conclusion:
"the 'high band' of the stereo imager looks alot like a 12db high pass filter!!"

Having this in mind and using the params on the MClass EQ for resonance can create a nice 12db HP Filter. Using 2 in a row creates a nice 24db HP Filter. I made a combinator patch that i put in a song:

It's .rps so you will have to copy it every step of the way. Be sure to copy all the numbers from the programmer, otherwise the resonance filter frequency isn't the same as the cut-off frequency or things like that.

One more note: due to limitations of the stereo imager, the cut-off frequency can only be set from 100Hz to 8000Hz. This will do 99% of all possible jobs but will constantly filter out all frequencies below 100Hz. Be sure to put the combinator on bypass when (at that moment not actively) using it on your master or on basses and stuff like that.



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