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not understanding bass string frequencies and crossover settings

Discussion in 'Live Sound [BG]' started by mr_flood, Aug 6, 2016.


  1. mr_flood

    mr_flood

    Mar 18, 2013
    So open bass strings go from roughly 40hz to 100hz. Crossovers are typically set at 100hz. Doesn't this mean that almost all of the bass sound is going through the subwoofer? Isn't this NOT what you want? Wouldn't you prefer your mids and highs to go through the typical dual 15 PA speakers rather than the subwoofer?

    Or, more likely, I'm completely missing something.
     
  2. Oh boy here it comes, duck and cover.
     
  3. mr_flood

    mr_flood

    Mar 18, 2013
    So there's some sort of controversy about this because I searched and couldn't find anything.
     
  4. Search waterfall plot. That is a graphical representation of the energy spread across the range of harmonics. Very broad as it turns out.

    If you unplug the mids and highs it leaves you with a strange woof like you can hear outside a soundproofed nightclub.
     
    Al Kraft and Bob Lee (QSC) like this.
  5. But we don't unplug the mids and highs!
     

  6. That would be true if the notes from our instruments were pure-tone sine waves. However, they are actually very complex tones, made up of the fundamental frequency plus harmonics and overtones. These are what produce the “tone” of the instrument.

    For instance, the open “E” string of a 4-string is about 40 Hz. Yet, you can hear this note when played through a cheap practice amp with a 8” speaker that doesn’t produce 40 Hz. You’re hearing the upper harmonics and overtones. Perhaps a more extreme example, ever notice that a Fender bass on old songs from the ’60s and ’70s manages to cut through even with the cheapest computer speakers?

    Thus, setting a crossover at 100 Hz, you’re still going to be getting a lot of bass information taking place in the main speakers that’s above that point. IIR, you’re getting into fundamentals in the 400 Hz range when you get into the second octave of the “G” string, and the crisp “smack” of slapped or pulled strings is up in the 3 kHz range.

    Regards,
    Wayne A. Pflughaupt


    Administrator, Pedulla Club #45
    Administrator, Tobias Club #133
    Fretless Club #943
    Big Cabs Club #23
    My Rig: Stage and FOH Friendly
    My Basses


     
    Al Kraft and Bob Lee (QSC) like this.
  7. mr_flood

    mr_flood

    Mar 18, 2013
    I got my answer, thanks for the waterfall clue.
     
  8. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    right (and not remotely a stupid question! this is actually pretty deep stuff)

    that 40Hz sine wave is actually a pretty small part of a bass guitar E note's output, you could roll it out entirely and it would mostly sound the same.

    also, no bass amp you'd find in a music store and that fits in your car really puts out much at 40Hz. just as well, because if it did you'd mostly just interfere with the PA mix and annoy your bandmates.
     
    fokof likes this.
  9. jimfist

    jimfist "Cling tenaciously to my buttocks!"

    Mar 28, 2011
    Boston, MA (USA)
    I've heard on more than one occasion from FOH mixers that finally, someone is giving them a direct feed that doesn't bombard them with too much low end. This is intentional on my part, where I put much more focus on the role of the broad midrange, which is much more important to the "punch" and clarity of the tone.

    Unless you're doing specific styles of music where sub-bass root fundamentals are key to the experience, for most other formats you don't miss much below 80hz, and trust me, 80hz can rattle your intestines. Commonly, the stage cabinets I prefer to use are designed specifically with very little reproduced below 80hz. If those frequencies need to be there, PA support can easily provide it.
     
    WayneP likes this.

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