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Thread: high/low shelf eq vs high/low pass filter eq

  1. #1
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    high/low shelf eq vs high/low pass filter eq

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    Can someone tell me what the actual different is?
    Honestly they sound exactly like the same thing.
    Im reading from a pro tools book:

    "a shelf equalizer affects a range of frequencies above or below the target frequency"

    "The high pass filter is useful for getting rid of unwanted low frequencies, and the low pass filter is used for eliminating unwanted high frequencise"


    If you were to use a shelf equalizer and set the gain infinitely low, wouldn't the shelf just become a filter?
    thanks

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    To your last question - yes - a high pass is a type of low shelf (in the way that a square is a type of rectangle).
    And with all digital paragraphic eq's you can pretty much set up a low shelf as a high pass (though not vice versa).
    If you're dealing with a hardware eq (which was all there was to work with when all these concepts were invented), it's just not practical to have a low shelf with controls that go to far enough extremes that it can become a high pass.
    Plus, they are generally used for different things - ie you toss a high pass on something that has some low end rumble you want to completely eradicate, you use a low shelf when you want to adjust the overall tone of the sound - like a "bass" knob on a hifi system.
    "Blindness isn't funny...
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    thank you that helps alot.

    SO then, when mixing, is it common in practice to apply the same high pass and low pass filter on the master bus or a submix bus? Because isnt there a standard range of frequencies that are always cut because no matter what they add muddiness or harshness?

    IE arent frequencies below 100Hz always cut and frequencies above 5kHz always cut, leaving you with a workable range from 100Hz - 5kHz?

    thanks!

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    Quote Originally Posted by emokid View Post
    IE arent frequencies below 100Hz always cut and frequencies above 5kHz always cut, leaving you with a workable range from 100Hz - 5kHz?

    thanks!
    Ummmm...no.

    All those bass drum hits that rattle the neighborhood everytime the moron with the subwoofer comes home are at 60hz. In fact, most peoples subwoofers only start working on frequencies below 80-90hz.

    5k is actually considered upper midrange.

    What you are describing would sound like a telephone.

    Now, there are individual instruments that you could put a high pass or low pass filter on, but that is really to get those instruments out of the way of the ones that need to occupy that frequency range.
    Jay Walsh
    Farview Recording. I am also the forum spokesmodel for Terasyne Amplification

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    The main difference between a shelf and a cut or pass filter is the shape of the EQ curve applied. A shelf is called a shelf because it kind of resembles a shelf; i'e. it flattens out at a certain level of dB cut or boost. Whereas a pass or cut applies a more-or-less continuous slope up or down of x number of dB per octave.

    For example, let's say you set a low shelf to cut low frequencies starting at around 60Hz. You set the amount of cut to say, 5dB. What will happen is starting somewhere around 60Hz, the EQ will slope down as the frequency goes down until it hits the -5dB level of cut requested and then level off at -5dB for the remaining lower frequencies. in effect creating a flat "shelf" of EQ cut at -5dB.

    A standard low cut/high pass filter does not level off - it does not create a "shelf", it instead keeps sloping downwards in a continuous csope as the frequencies lower until either we run out of frequencies or run out of volume.

    Of course they both work the same way but in the other direction when boosting instead of cutting.

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