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Banishing bass sound..

Discussion in 'Live Sound [BG]' started by hyoshim, Jan 12, 2013.

  1. hyoshim


    May 5, 2004
    Los Angeles
    While I was walking around (back and forth) inside the sanctuary with bass playing the open E string, I noticed that the bass sound simply banishes about in the middle of the room. It sounded like some sort of cancellation was going on. I was thinking may be the standing wave in the room is canceling my bass. If that is the case, what would the fix for it?
  2. BrBss

    BrBss Supporting Member

    Jul 9, 2010
    I think you mean "vanishes", not "banishes". You are correct, it's likely due to standing waves. Are you playing through an amp or direct into the PA? Try moving the speakers from where the bass is coming; if you're through an amp try moving it near a corner if possible. You can also address the problem with acoustic treatment of the room, but that's probably not feasible here.
  3. wvbass


    Mar 1, 2004
    You have a cold or something?
  4. EQ adjustments always does it for me. Too much midrange is often all I have to adjust to clarify the bass throughout a venue.
  5. hyoshim


    May 5, 2004
    Los Angeles
    Thanks, and I was playing through a GK 700 combo, 2x10 which was placed not at the center (left side). The wall is basically smooth concrete with no acoustic panel of any sort. May be it will be better with the congregation filling the room or installing acoustic foam on the wall may fix?
  6. seamonkey


    Aug 6, 2004
    Look up boundary effect. Moving your amp a foot or two can make a big difference.

    Best, when the sanctuary is empty, put your bass amp out where you are concerned with getting the best sound to somebody sitting. Like in the middle. Then walk around the stage, move your head higher and lower, until you find the best sound. Put your amp on stage where your head hears the best sound.
    If you're cell phone has a decent SPL app, that handles bass frequencies you can use it as a sound meter to confirm what you hear.
  7. hyoshim


    May 5, 2004
    Los Angeles

    I looked it up and it refers to basically increase of the low frequency up to 12 dB depending where you are sitting (hearing). In my case, it "vanish" or reduced down to almost zero. Anyway, thanks for the responses. I am learning a lot ^^*
  8. Pilgrim

    Pilgrim Supporting Member

    Having a number of people in the room makes a big difference because they are soft objects which break up sound waves and also absorb some sound. Sound bounce (and cancellation due to waves reflecting into each other) will change a lot with people in the room.
  9. craig.p


    Sep 28, 2008
    New Hampshire
    Thought I'd ask whether you're also going through the PA.
  10. He's Spanish...:bag:
  11. hyoshim


    May 5, 2004
    Los Angeles
    Nope, I was only going through my cab.
  12. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    a single 2x10 cab? no wonder.

    is the rest of the band in the PA (especially the drums)?

    does the PA have subs?
  13. craig.p


    Sep 28, 2008
    New Hampshire
    Thanks for the answer on the PA. Glad to hear you're using only your amp. Too many sanctuaries do the low-end portion of their PA (and sometimes even the low end of their on-site organ) all wrong. Going through a poorly-architected PA often comes out worse than forgoing it altogether and relying instead on the bass amp. Even worse would be going through both at once because of the additional phase anomalies, unless the bass amp were being run quiet to act only as the player's personal monitor.

    Some sanctuaries are just not "fixable." They were built for one job: to carry a minister's voice to the back rows. They do that well. But for the same reasons they do that well, they often stink at supporting a full band's low end.

    The sanctuary I play at has high hard walls and a tall (50' more or less) vaulted ceiling. Also strict rules around where the amps can be located. So, you can hit a loud note, check your phone for text messages, and when you're done, that note is still wandering around looking for a place to land. Getting a decent BG sound anywhere in the room under those conditions -- let alone everywhere -- is just not possible.

    So, a lot of this has to do with managing expectations in light of architectural, stage-layout, and budgetary constraints.
  14. uhdinator


    Apr 20, 2010
    Because freq's below 100hz or so are omni directional.......

    Having a bass cab 3.5' above the floor, and 3.5' from a back and side wall.
    That gives you 3 boundaries that are canceling 80hz.

    Place bass cabs or subs either 7' or more, or less than 3' from back and side walls.

    The formula is speed of sound at approx 68-70 deg F 1130 ft per sec
    Divided by freq 80hz= 14.125
    Divided by 4 = 3.5'

    1/4 of the wavelength distance causes cancelation. The wavelength bounces/reflects off the wall/boundary
    And the reflected wave is out of phase with the original, canceling a lot of it.

    1/4 of a 40hz wave length is 7'.

    Placing LF cabs close to boundaries can increase output.

    Boundary cancellation
    Boundary coupling
  15. 4StringTheorist

    4StringTheorist Supporting Member

    There will always be spots of destructive interference. When I demonstrate waves each year, I let my physics students wander the room while a 50Hz or 60Hz tone plays through my amp. There will be super loud spots (constructive) and super quiet spots (destructive). It's unavoidable. But, that spot that your open E is inaudible in? That spot is specific to that frequency. Your lowest A is likely to be entirely audible there.

    So it's a problem you can't eliminate, only minimize with the tips others have given you here. And, no one listening will be unable to hear you play.. they just might get a few notes here or there dropped out.
  16. ReiPsaeg


    Dec 1, 2012
    Rochester, NY
    And to add to that, going from physics to psycho-acoustics, if anyone is listening from that spot in the room, their mind will actually fill in the missing frequencies.
  17. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    The last three posts both hurt my head and made me smile. I'm taking my stupid butt to bed.