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Low freq bump on HPFs

Hi!, Í wanted to know if anybody could explain why is there a low freq. bump when applying HPF to sources on mixing. My experience is that sweeping on the low range I can find a cutoff freq that, not only removes energy, instead it increases presence.
In other words, by removing low freq rumble I actually can have more Low or mid low presence.
I notice the effect more dramatically on percussion chanells like snare, mostly around 80 Hz.
Be it Pro Tools, the Sony DMXR100, or whatever, there is a cutoff freq that can make this happen.
Am I missing something?


Profile picture for user RecorderMan

RecorderMan Fri, 07/26/2002 - 06:52

Hi Marcelo,

First, cutting frequencies can let other bands in the spectrum be heard better. Second, many filters (even digital models...filter bank as an example) mimic the way transformers work. At the knee frequency (where the dip starts to happen....usually noted at the point 3db down into the cut) Transformers-depending on there characteristics- can "ring" or oscilate ever so slightly, thereby causing a reinforcement or "boost" around that frequency. Playing with this is definetly one of the things ou use/listen for when filtering.

An extrapolation on this, is to filter and also boost on another bell shaped EQ at frequencies at or jsut beloe the filter freq's. Great for gtrs.

Marcelo Fri, 07/26/2002 - 19:59

Thank you!!!, It is funny!, because I do that a lot on GTRs, Removing Hi freq,and compensating with a slight boost below the cutoff.
Feels like on going the right direction.
Greetings from Argentina.