Off-Axis Problem

Discussion in 'Amps and Cabs [BG]' started by BassWizard55, Jan 14, 2003.

  1. BassWizard55

    BassWizard55 Guest

    Dec 21, 2002
    Rome, Ga
    I have a GK 700RBI 210, which is really nice and I love it; but I was playing on it the other day, in an auditorium, and I swear, I had it cranked and could barely hear it unless I was standing right in front of it. Directly in front, it sounded huge. My band practices in a small room, and It sounds fine and loud enough at 10'clock on the volume knob.

    Is this common? Does anyone else's amps project nearly 100% of the sound on axis?
  2. Were there any boundaries next to you, or your amp, other than the floor?

    Bass amplifiers and subwoofers are sensitive to the boundary effect. When a low frequency cabinet is next to a boundary such as a floor, floor + 1 wall, or floor + 2 walls (in a corner) this effect is quite dramatic. More boundaries = more bass apparent to the listener. Try it sometime, put your amp in the corner of a room, & listen. Then move it to the center of the room, set it on a stool or something similar, & listen.

    Also, the boundary effect applies to the position of the listener. Play some bass-heavy music in a room, now walk around the room, putting your ears next to walls, near the corner of the room, near the center of the room. You'll see, it's a big difference.

    I'm guessing that your amp was coupling with the floor of the auditorium, and when you were right in the 'vee' of sound (imagine one leg of the vee going across the floor, one leg of the vee going parallel to the amp's baffle) you could hear your bass well. Once you left that 'vee', the apparent spl was lost.

    The fact that low frequencies have long wavelengths - this also applies, but I don't know much about it.

    Hope this helps.


  3. BruceWane


    Oct 31, 2002
    Houston, TX
    All you could hear was the direct sound coming out of your speakers because effectively there were no reflections coming off the walls.

    You're experiencing the effects of room size. Let's say you're practicing in a room that is 200 square feet, and your rig sounds great, really fills the room well. Unfortunately, to do the same thing in a larger room, you basically need the equivalent of one rig per 200 square feet. While you wouldn't need to fill an entire auditorium with sound (that's what PA's are for), you do need to cover the stage area. Aside from the fact that most stages are larger than most practice areas, they also are not enclosed, i.e. they are open on the audience side, so your sound disperses rather than reflects. It's also very common in the practice room to have your amp against a wall or in a corner, which signifigantly boosts your output. Most stages you pretty much have to put your amp out in the middle of the floor; if it's not within a foot or so of a wall or corner, you get a lot less help from "room gain". There aren't any walls close enough to contain the sound waves.

    Playing outdoors is an even tougher ceiling.......
  4. BassGreaser


    Aug 22, 2002
    Austin, TX
    yeah outdoor gigs are not for for a bass player........