Low Pass Filter Use

Discussion in 'Production' started by IV4, Nov 19, 2012.

  1. IV4

    IV4 Currently a newt.

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    Most of us know that you should High pass almost everything that might conflict with the bass and always cut off everything below 30hz. What about low passing everything?
    Two songs ago, that I had made, I put a low pass cut off on everything at 6khz. The first thing I noticed was how clean putting the cut off at 6khz made the mix. The second thing I notice was everybody who left feedback asking "Where are the hats?"
    At this point and time I know it is a good idea to start cutting everything off at the top. My question is, how high should things go? At what point in the freq spectrum do we not truly hear anymore, and at what point we can hear, just strains the ears? For my kick, snare, and bass 6khz seems like a good place to start with the cut off. For my hats somewhere between 13khz and 18khz seems like a good place to cut off.
    Has any one tackled this question before and have any sound advice?
    Thank You and Discuss
     
  2. Dugg Funnie

    Dugg Funnie Well-Known Member

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    I can't remember who the artist was, but I was watching a masterclass once and he low-passed nearly every channel around 19kHz; something to do with those frequencies not coming through in the master vinyl press anyways so might as well duck them out for headroom.
     
  3. JimpaDirt

    JimpaDirt Vettvilling

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    Intresting... a trick would be to lowpass evrything where it feels comfortable then and just get some really clean hi-hat samples for the top end perhaps? I've never experimented much with cutting the highs.

    And oh, the human ear can hear between 50 hz - 20khz, thats what I got thaugt in school anyways. Tho our frequencyrange lowers as we get older so only new born babies can hear around 20khz basically...
     
  4. djSing

    djSing Ill-usions

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    I often use a final EQ on the master to boost the mids slightly and cut the very high end, usually chop off anything above ~18hkz, though it can be different for each track. Cutting everything off above 6Khz is gunna seriously knock the impact out of your percussion and high end shit. Human ears can hear up to around 20Khz, those very high frequencies aren't really desired though.

    What I do is use a high cut with maximum gain reduction, then I change the Q (what the fuck does Q even stand for?) to sharpen the bandwidth so it starts to reduce the gain around 17-18k. You have to listen out for when those very high frequencies start to diminish, you only want to reduce them slightly enough so that they are still crystal clear but not ear piercing.

    All of the above could be wrong, its just the way I do things

    D:
     
  5. lostnthesound

    lostnthesound Burns Easily in the Sun

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    Great question and I agree in that Low/Hi Passing are invaluable tools for the mix. I've actually been using them as a means to control "volume" rather than automating the volume faders and have found that it produces very smooth results.

    As far as where to start cutting off the high frequencies...I'm not too sure honestly as I've heard many varying answers. Personally, I slowly cut back on the highs until I begin to hear the audible difference, and then I'll add back just a bit. I apply this technique to high hats, snares and kicks that need the "click" softened up a bit.

    I remember one of Olav Basoski's MacProVideo tutorials where he discusses the nature of editing in a digital realm and how there is already an abundance of high frequency information present, most of which can't even be picked up with the human ear. Since then, that's how I try to approach mixes and sound shaping–trying to remove as much hi-end without taking away from the frequencies that add presence, air, etc. To add, I would spectulate (and someone please correct me if I'm wrong) that when that mix goes to get mastered, the engineer will work his gain/frequency/dynamic range boosting magic to fill out those higher frequencies that you attenuated without making it sound unnatural.

    Here's a couple resources you may find of interest:

    Frequency Chart 1
    Frequency Table
    Frequency Chart 2
    Interactive Frequency Chart

    Cheers.
     
  6. Binary_UK

    Binary_UK Binary.

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    Interface most likely, remember him chatting about that :)

    Sent from Andy C's trucker hat using Tapatalk.
     
  7. Fluff

    Fluff Active Member

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    Q is a measurement of the effect of resistance to oscillation. High Q values are very resonant (ringing) while low Q are well damped.
     
  8. Innovine

    Innovine Active Member

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    You might not hear frequencies above 18-20khz, but that doesn't mean there's nothing going on there. If you don't lowpass it away, those frequencies can alias when downsampling or run through effects and become audible noise.
     
  9. Mr Fletch

    Mr Fletch aka KRONIX

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    As a rule, I tend to cut everything above 16khz as this is the point that is inaudible (as far as I know), and as already mentioned, anything below around 30hz. If you cut everything above 6khz then that is why you will be missing the hats etc from the high end.

    Almost any sound created within a synthesizer, or any audio you use will output high frequencies, even if you cant hear them, its a process which happens within the cpu when processing the different sound waves, it's like an inaudible "digital high end" frequency that can cause alot of mess within sounds if they arent cleaned up. You wont notice it on individual sounds, but try layering up several un-EQ'd mid to high frequency sounds and you'll be surprised at the amount of "white noise" that becomes apparent.

    Obviously where you cut depends on personal preference, but yeah, 6khz is way too low, id say anywhere from about 10khz upwards is fine. But I found the cleanest sounds when cutting at 16khz
     
  10. motion audio

    motion audio Active Member

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    Not in terms of EQ controls. The Q control on an EQ is the bandwidth of the curve. So how much either side of your selected frequency is also affected by your cut/boost. A low "Q" will result in a notch where only a small range of frequencies are changed, and a high setting will result in a much wider range of frequencies being pulled in. If you were taking out a resonance at a specific frequency, you'd use a low setting to tackle just the problem area. EQing something for more creative reasons you'd use a higher setting and less boost/cut for a more natural sound.
     
  11. Fluff

    Fluff Active Member

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    I disagree. A more resonant system (i.e. one with a high Q) will ring at the frequency of resonance and will typically result in a sharp peak at that frequency while a low Q EQ boost is spread across a greater range of frequencies