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Track level getting LOUDER (and clipping) when I high pass it?

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I was examining the frequency content in a mix (a single wav file of the mix). I did a low pass filter at 1120 Hz and as you'd expect, the highs got cut! However I noticed that when I engage the low pass filter, the peak level of the track during the 4 bars I have looped up which was previously 0.0 dB changes to 0.1 dB. That is, the signal gets louder when I cut everything above 1120Hz.


Then, when I turned on the high pass filter, the peak level of those 4 bars went up to 3.8 dB and some very audible clipping started occurring. The funny thing is, the high pass filter was barely even cutting anything. As you can see from the attached image, the HPF was basically doing nothing and it was resulting in + 3.8 dB of gain.


When I bypass the HPF everything sounds normal. Although the LPF is still causing a 0.1 dB gain increase as I mentioned earlier. But that is not causing any audible clipping.




What could be the cause of this?



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Indeed, when using a smooth 6db/oct curve this will not happen. A 48db/oct low cut (depending on the plugin manufacture) can cause such effect because of it's characteristic.

The effect can be very drastic on 808 kicks f.ex. The only digital Eq I'm happy with (even at 96db/oct) is the Fabfilter Pro Q2. I really like and use Logic's Eq a lot but for this kind of precise low-cut it's not doing it.

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