Why am I getting sound cancelling through my mixer?

Discussion in 'Location Recording' started by Mrtechnicalskills, Dec 5, 2009.

  1. I have sound coming out from outputs 1 and 2 from my Hercules DJ Console RMX I have already tested the output sound and know that it is working correctly.

    I used the two 1/4" aux outputs, each one to a channel on the mixer.

    When the sound is playing through the mixer with both channel volumes up, the bass sound is completely cut!

    What is stranger is that when the volume on only one channel is up the bass kicks in again. It sounds to me like when both channels have the volume up they are cancelling each others the bass out.

    Why would this happen?

    I ultimately got the sound to work by panning one channel completely left and the other completely right, but I still don't understand why the channels would cancel out only the bass.

    -Kurt
     
  2. natural

    natural Active Member

    There's a couple of possibilities, both have to do with polarity. (what some call phase reversal)

    a- There's a good chance that one of the two cables that you have is wired incorrectly. (tip on one end wired to the sleeve on the other end)

    b- One cable is a TRS cable while the other is the typical TS

    c - Cable is not pushed all the way in (ck all 4 connections)

    d - Some other anomaly based on conditions yet to be discovered.

    (actually, I guess that's more than a couple)

    Oh, and to answer your question as to why the bass disappears. Anything that's common to both channels (ie, anything panned to the middle) get's canceled out by the reversed polarity when panned to mono. When in stereo you can hear everything, but it probably sounds a little weird. Sort of super stereo maybe. Because of the reversed polarity on one of the cables, while one speaker is pushing forward, the other speaker is pushing backward.
    Your lesson for today is to research "Phase Cancellation" "Phase Reversal" "reversed polarity"

    keep us posted.
     
  3. BobRogers

    BobRogers Well-Known Member

    What kind of mixer? Do you have a phase inversion switch on one channel?
     
  4. natural

    natural Active Member

    oh yeah, I guess that would be [d]
     
  5. Sorry for being MIA.

    Thank you very much for the information.

    The problem must have been the wiring in one of the cables but I do not have that specific cable anymore so I guess I'll never know.

    It works fine now though with different cables.

    So from what I have learned I'm guessing that the one cable what wired incorrectly so it was off phase with the other cable causing phase cancellation.

    THanks,
    Kurt

    p.s. mentioning TRS and TS is also helpful for the future.
     
  6. sheet

    sheet Well-Known Member

    Actually, you had inverted polarity, which is different than something being out of phase. Two signals out of phase can have the same polarity, but not the other way around.

    Just so you know.
     

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