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Phase cancellation (out of phase with FOH or foldback)

Discussion in 'Amps and Cabs [BG]' started by remo, Oct 3, 2005.

  1. remo


    Jan 15, 2005
    I recently fitted a new crossover to my Avatar 212 and accidently wired the speakers out of phase with each other when I put it back together (doh).. this resulted in a really hollow and empty tone (I knew the problem instantly)..

    anyhow it made me wonder if anyone has encountered a situation where their cabs were out of phase with either the FOH speakers or the foldback speakers (if any bass was coming through foldback) and it totally killed their monitoring level and made their beefy tone disappear into the either. :confused: :confused:

    I once had a horrible situation where I was getting masses of bass feedback through the FOH when ever I played a B note anywhere on the neck (regardless of octave!).. it just howled and the room felt like it was taking off!
  2. Yeah, this is not an uncommon problem, although I've had more trouble with the bass from the drummer's monitor drowning me out (hearing more of myself from that than my own rig right in back of me). If you can hear a problem, you've got to take action to correct it, because chances are you'll be the only who notices it. If it's a FOH issue, you could alter your setup position (up or down stage, for instance) and see if sound to your ears cleans up. A good mixer setup (either foldback or FOH) will have phase (more correctly polarity) invert switches on each channel, and you could ask one of the soundmen to try flipping that and see if things improve. If you happen to have an amp/speaker that's using banana plug connections, you could do the flip there as well. Whatever gits-R-done quickly and effectively.
  3. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    That would have been caused by a soundman with an inadequate quotient of grey matter. He simply didn't have enough sense to pull down the EQ slider at the offending frequency. Chances are he boosted the bejesus out of the system at 64Hz to accentuate the kick and didn't cut the EQ on the bass channel to compensate.