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Source Audio EQ work as HPF/LPF

Discussion in 'Effects [BG]' started by Blu bro, Oct 28, 2018.


  1. Blu bro

    Blu bro

    Mar 1, 2012
    Aus
    would love to hear from someone who owns the SA EQ. Can it be used as a HPF and LPF?!

    What EQ points are generally used for this application?
     
  2. 40Hz

    40Hz Supporting Member

    If you mean the programmable EQ, I have one. The extended range option to set the lowest EQ point to 62Hz puts you into HPF territory. The average HPF covers from around 200Hz down. But most players using a HPF set it somewhere between 25Hz and 60Hz. I’m also not sure the slope of the EQ is steep enough to effectively act as a HPF. But it hurts nothing to try it if you already have one.
     
    Last edited: Oct 28, 2018
    Blu bro and Stumbo like this.
  3. Blu bro

    Blu bro

    Mar 1, 2012
    Aus
    unfortunately I do not have one. More of a curiousisty question than anything..
     
  4. 40Hz

    40Hz Supporting Member

    Curiosity is a good thing when it comes to gear. The more you know the more grief and money you’ll save yourself in the long run. :thumbsup:

    With a HPF or LPF the attenuation is pretty dramatic as opposed to the more gradual boost/rolloff slope on a graphic EQ. Whereas a graphic EQ has a smooth ramp of sorts, a bandpass filter has a very sharp cutoff, which is why they’re sometimes called brickwall filters. They are primarily designed to hard block every frequency below/above their setting. It’s like those frequencies hit a brick wall and are stopped cold. Like a parametric EQ, bandpass filters are surgical in their precision when it comes to zeroing in on specific frequencies. Graphic EQs focus more on a range of frequencies, each centering around a fixed series of preselected frequencies that are hardwired in. You also can’t control the shape or width of the curve surrounding the EQ points each slider centers on. So while it’ll cut something you want, it’ll also affect frequencies on either side of that center frequency. So there’s a potential for something you don’t want to cut getting dragged along for the ride.
     
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  5. Blu bro

    Blu bro

    Mar 1, 2012
    Aus

    thanks, I think this answers my question. I didnt think about "shelf filters" and "notch filters" good point.
     
  6. Stumbo

    Stumbo Wherever you go, there you are. Supporting Member Commercial User

    Feb 11, 2008
    Song Surgeon slow downer. https://tinyurl.com/y5dcuqjg
    Passinwind said:

    I figured out for myself though, that I really dig sealed cabs
    Ironically, I don't own one atm, but the db410 I do own has a pretty cool tuned port that does not go very deep, afaik it rolls at slightly above 40hz which almost makes it sound like a sealed cab but a tad deeper. In other words, it sounds tight.

    An Eq with a 20-30hz centre should basically do the same thing.
    I agree that the hpf does it better, but chances are you are going to have tough luck actually getting one.

    FWIW, here's a model I made of the difference between a ten band graphic EQ pedal with the low fader (32Hz IIRC) all the way down (-10dB), vs. a 4th order HPF with a -3dB point at 32Hz.
    10Bandgraphic_32Hzcut.
    HPF_32Hzminus3dB.


    It doesn't do the same thing, dropping this 30Hz band down 12dB would mean that the signal is ~6dB down at 60Hz and maybe 3dB down at 100hz (depending on the topology of the eq circuit).
    A 4th order HPF set at 30Hz will be 3dB down at 30Hz, almost 0dB down at 40Hz and 24dB down at 15Hz.
     

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