Cutoff filters increase the volume???

Hi guys!
This is a problem I’ve had since I started making music. I produce House music and I like to use any means to tidy up my song, so that I can make it that bit louder during the mastering process.

In every other tutorial people tell u to cutoff the lowest frequencies of any instrument (20 - 25 Hz), because they need alot of energy and space in the song, but we can’t hear them or even just feel them. But every time I set a cutoff, the volume of the sound actually goes up by 1 to sometimes even 3 db, without any hearable difference (it sounds a bit thinner but in no way louder)! And it’s not only like that with the bass-frequencies. This effect is strongest when I set the cutoff near the root of the sound and decreases the further away the cutoff is. Only after a few thousand Hz the volume actually decreases like it should. How can that be? I mean, if I cut something OFF, then there should be LESS there afterwards, no? O_o

I don’t think that this is due to a too high Q. I always turn the Q only so far up, that there is no hill visible on the curve. I’m using the StudioEQ from Cubase 5, but another EQ I tried (Gliss I think) does the exact same thing. Is this normal, some weird bug, or simply what u get from using low quality EQs (people say that the Steinberg EQs aren’t the best, but I’m not sure if that’s really true)? Any help would be greatly appreciated! Thx!

Ok, I found some other threads concerning this topic while googling. It seems that this volume increase on lowcutting is a problem with most EQs that are not phaselinear. The effect is obviously greatly decreased when using a phaselinear EQ. Maybe I’ll try to get my hands on one of these next.