FabFilter User Forum
48dB hi cut slope causes boost in level?
Hi,
I was using Pro-Q2 yesterday and noticed that simply using a single 48dB slope lo cut with the Q button at 1.0 caused an increase in my signals peaking.
I suspect there is a resonance on the high side of the cut off point, and so I'm wondering why the curve graphic doesn't display the resonant "hump".
I'd like to think that the graphic display is accurate or at least attempts to display the different implications of using the various filter and pole configurations.
Any thoughts?
Thank You.
mike_mccue — Oct 4, 2014
The boost in level is due to the removal of the low freq... It seems illogical but due to the phase cancellation of different freq in the original signal, when you remove some freq that cancellation doesn't occur. So it's quite common to filter low freq and have an overall boost in level. Also, if you're on a non-linear mode, the phase shift induced might also exaggerate this.
There's no resonant hump, the GUI is correct.
Hi Mike,
Ross is indeed correct. EQ filtering changes the signal, and changes the phase of different frequencies in different ways. And as a result of this, you can easily get (slightly) higher (of lower) peak values :-) This is totally normal!
Cheers
Thanks to both of you for explaining. I have never considered this idea before and am enjoying learning more about this aspect of EQ filtering.