Dynamic lo/hi-pass filter... does it exist?

YanKleber

Retired
I know that lo-pass and hi-pass filters should be applied in the tracks to cut off the not used frequency range.
Does not exist some kind of dynamic filter that scans the track as it goes and apply the filter automatically?
As far as I can understand it would be just a matter of cut everything that is outside the audible range, right? It doesn't seem to be a hard task for a VST.
Just wondering...
 
Well, except for the problem of frequency. You wouldn't cut your bass kick the same as your cymbals. Automating according to what is "seen" in the frequency realm won't work either, as some harmonic frequencies that are visibly large sometimes need to be cut for good tone. VSTs can't "hear" they can only "see". Therefore, they are not able to discern "good" harmonics to keep vs "bad" harmonics that need cut. :D
I'm sure the math is out there to make it close, but experience and experimentation will make better music than math. Music is part science, but mostly art.
 
You could do it in theory, but there would have to be plenty of buffering to allow enough look ahead for the change to be implemented in time. Think of a bass playing lots of low notes, then sliding way up high. Also, distortion on a guitar introduces all kinds of high frequency content that would require major tweaks to the sensitivity parameters of such an effect. And now the kicker (pun intended) is that anything with a sharp transient inherently has tons of high frequency information for very short bursts. The FFT of a pure impluse is a constant value across all frequency, so the program would see the transform of the impulse response, see all that high frequency content, and not filter anything; or filter it out and your transient sounds like crap. It would have to be an incredibly smart algorithm. Not impossible, but there will still be tradeoffs that have to be made. Also, do you really want a software developer essentially determining what is getting cut and not? I would rather decide it for myself, but that's me.
 
What's a 'track'? A song track or track in a mix..? Maybe it doesn't matter.
But yes, it's called a dynamic eq. Whether whats out there also have HP LP options of filters in their choices.. hmm, maybe not. Have to have a look at the usual suspects.
Typically you'd pick a suitable high or low pass and stick with it. Dynamic eq tends to be applied for different sets of uses than HP/LP.
 
The math'? Well, yeah.
The question is.. what's really the app? ('filter 'content that doesn't exist'- dynamically no less. unclear at this point :D

wait a min.. that won't work. Where do you put a threshold for 'nothing to detect' :rolleyes: Never mind.. :p
 
The math'? Well, yeah.
The question is.. what's really the app? ('filter 'content that doesn't exist'- dynamically no less. unclear at this point :D

wait a min.. that won't work. Where do you put a threshold for 'nothing to detect' :rolleyes: Never mind.. :p

But basically this is not what lo-pass and hi-pass filters do? Remove contents that theoretically doesn't exist? So what's the point on use them? As far as I can see the only difference is that a lo/hi pass filters keep seated on the freqüency you set it while a dynamic filter would widen and narrow the range to better fit to the track.

Nonetheless I fully agree with someone that has said that while we hear something the digital filters 'see' it and that theoretically it could ruin the harmonics. By the other hand I don't think that there is a real difference between what human ears here and a software sees because all the digital filters out there has proven to work correctly. Also, theoretically speaking, a lo-pass and a hi-pass filter can also ruin the harmonics. Not?

Please don't get me wrong. I am just a newby trying to understand what is the point of doing some things.

:)
 
As far as I can understand it would be just a matter of cut everything that is outside the audible range, right?
Well, that's not really how you use them. You use them to cut frequencies that are not necessary to the sound of what ever is on the track.

If it is outside the audible range, you wouldn't hear it if something was there AND it is unlikely that it would have gotten recorded anyway. Unless you accidentally had someone playing a dog whistle in the background and you were recording at 96k, it's unlikely anything inaudible got captured.
 
But basically this is not what lo-pass and hi-pass filters do? Remove contents that theoretically doesn't exist? So what's the point on use them? As far as I can see the only difference is that a lo/hi pass filters keep seated on the freqüency you set it while a dynamic filter would widen and narrow the range to better fit to the track. ..
Farview already covered the main point -the distinction in when or why they're used, but to reiterate, no. They're used to remove or lessen unwanted content, or to 'trim or shape the content (as any tone control). There is the thought too some like to take of 'even if I don't necessarily hear a problem, apply them as 'cautionary'.
But always (oops, never say never :rolleyes: :D ) - control content.
 
Back
Top