I just figured this out by accident. On my latest track, I added a Fabfilter Pro-Q 2 on the master just to do the usual low-cut/high-cut and remove some ringiness. I forgot to do it before I rendered the track, so I re-opened the project and added the EQ. The thing is after I did the eq-ing, my kick started to sound different each time it hited. I thought it might be just in my head, but after several listens, I found out it's not. The eq was affecting my output. And I decided to make a short test.

I took several tracks, applied an EQ plugin on the master channel and (very important) started to low cut/high cut (basically "cut" some frequencies). I was very surprised to see that my master gain blew up by 5-6 dbs over 0! Now the question is... WHY? I didn't add any dbs, didn't boost anything. On contrary, I cutted out some frequencies that weren't needed. I tried this with Fabfilter Pro-Q (1 & 2) and with Ableton's stock EQ Eight. I even tried all the different processing modes from Fabfilter (Zero latency, Natural Phase, Linear Phase). It did the same for the "Zero Latency" and "Natural Phase", but it worked better with the "Linear Phase" mode activated. The thing is the "Linear Phase" adds pre-ringiness, which I obviously don't want.

Can someone please explain the "magic" behind this? Why is the output going red (by so many dbs lol) when doing frequency cuts?

i think mussar made a post or put a link to something related to this phenomena, but on a smaller scale, a few months ago.


If you EQ out a compressed sample (rendered sample) it might have the tendency to increase in volume.

you also have to check how the EQ works.

I use reason, which has an SSL emulation console, and when ever i make a drastic low cut, the the highs on my EQ actually increase in gain, with out having applied an increase in the high cut.


also, if it's a FILTER you're using, there's probably some resonance that's being boosted near the cut off frequency that you have not accounted for. and a simple fix, if you have a controllable resonance or bandwidth parameter, is to just adjust it to where it's not boosting, or adjust your master/mix to that particular boos in sonic content.

Yes, that's exactly how non-linear phase EQs work, and yes this happens due to a phase shift near the cutoff frequency.  However, if you only do minor changes with a wide Q, you should be fine.  Sharp cuts may mess up your low end, so it's better to avoid them on the master (my opinion).