Hi-pass filters on the master fader?

Discussion in 'Mastering' started by ENW, Apr 30, 2008.

  1. ENW

    ENW Guest

    High Pass Filters?

    I was looking at a frequency analyzer while playing a few commercially released tunes. I noticed a stark drop-off around 20 kHz.

    Is anyone out there using a high pass filter at 20 k? If so, why?


  2. danbronson

    danbronson Guest

    I'm listening to a record with a high pass filter on 20 kHz right now. It's called silence.

    I'm assuming you mean 20 Hz?
  3. Cucco

    Cucco Distinguished Member

    Fredericksburg, VA
    Or Low Pass filter...dessimation filter...brick wall filter for DAC??
  4. hueseph

    hueseph Well-Known Member

    Dogs don't buy cd's. Can you hear beyond 20kHz? I know I can't. With my hearing degradation. I have trouble hearing beyond 15k.
  5. bent

    bent No Bad Vibes! Well-Known Member

    Cocoa, FL
    Home Page:
    Commercial tunes off a standard CD - there's an LPF in place prior to the Nyquist freq. (Nyquist = 22.05K (half the sampling rate @ 44.1k)).

    In short, yes - we are using an LPF around 20k.

    For future reference -
    An LPF (Low Pass Filter) cuts out high frequencies.
    An HPF (High Pass Filter) does the opposite.
  6. ENW

    ENW Guest

    Hello Bent,

    Sorry, I meant low-pass filter.

    You da man. Thanks for your expert advice. That's what I suspected from what I was seeing on the analyzer. My degree is in music. I did not know this about Nyquist...

    "In order to recover all Fourier components of a periodic waveform, it is necessary to use a sampling rate at least twice the highest waveform frequency. The Nyquist frequency, also called the Nyquist limit, is the highest frequency that can be coded at a given sampling rate in order to be able to fully reconstruct the signal (Wolfram Math World)."

    LPF at half the sampling rate. Got it.

    Thanks again,

  7. bent

    bent No Bad Vibes! Well-Known Member

    Cocoa, FL
    Home Page:
  8. Codemonkey

    Codemonkey Well-Known Member

    Scotland, UK
    And a HPF at 10. Just to keep the audiophiles happy and the subsonic-DC-offset-esque crap away.

  9. cerberus

    cerberus Active Member

    codemonkey; the ear cannot process pitch information below 20hz.
    in musical terms, there are no notes down there, so we
    may call the subsonic component "noise".

    subsonic signals also stress out the playback amp much more
    than audible freqs. so "unheard" (but perhaps felt) subsonics
    may cause a playback amp to distort at lower overall

    for these reasons, we may wish to apply hp filters in mastering but
    probably not eliminate subsonics entirely, as many instruments
    do produce subsonics; and taking into account that timbre
    can be affected by removing or adding noise.

    my advice here: use your ears, not your eyes to
    make this judgement call.

    jeff dinces
  10. BobRogers

    BobRogers Well-Known Member

    Blacksburg, VA
    Back in the 70's I had a friend who had built a big sub for his stereo system and had some way of sending a 5 Hz to it. If you didn't know he was doing it you couldn't really "hear" it, but you could sense something was wrong. He used to joke that he played it when his mother in law came over.
  11. Codemonkey

    Codemonkey Well-Known Member

    Scotland, UK
    Oh man. 5Hz sine waves rattling your windows and walls.

    Can dogs hear that low or is it only 20kHz+?
  12. ENW

    ENW Guest

    I have a friend who is a church organist. He says you can't hear the really low pipes but you can feel them hit you in the chest.

    That's a hoot about the mother in law.
  13. Codemonkey

    Codemonkey Well-Known Member

    Scotland, UK
    Times like this I wish we had a real organ. It's a keyboard/electric organ thing which has a nice sound via the Line Out but lacks in physical presence. It's tucked into a corner which sucks, and until I got hold of it, it sounded lousy.
    The PA can't help with the LF stuff (it fills the church well enough) but I roll off the lows and add some mid/highs using the better placed speakers.
    Sounds crap in recordings but good enough on Sunday mornings.
    (If I want a non-rolled off version I need to hijack the Insert)

    Shows you the difference 5Hz makes though.
  14. Cucco

    Cucco Distinguished Member

    Fredericksburg, VA
    One of the organs I record regularly has a few real 32' pipes and a couple digital 32s and digital 64s (yup...64s). The nice thing is, the space is big enough to really get those 64s working with the room. When they kick in, you can feel the marble vibrate. Of course, the other 9500+ *real* pipes don't hurt with that either...

    Yeah, you'll definitely feel the vibes from the biggest pipes...

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