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phase

Discussion in 'Recording' started by swansonic, Mar 5, 2001.

  1. swansonic

    swansonic Guest

    What is the quickest way to check phase on a couple of mics (eg. drumset) on a mixer without a phase button? I have made a short mic cable with reverse polarity to put in series one cable at a time. Is there anything that you could quickly plug into the insert on each channel for checking phase? I'm using a Mackie 24*8.

    Thanks
    Mike
     
  2. sapplegate

    sapplegate Active Member

    Joined:
    Mar 5, 2001
    I believe your Mackie inserts are single-ended unbalanced, so you can't just cross the wires (there aren't enough to cross!)

    You could build a signal inverter with an op-amp, a few resistors, and two 9-v batteries. Stuff it in a small project box with a TRS pigtail cable and voila! Wire the op-amp as a unity-gain inverter. The quality won't be great, but if you are using it as a testing device, who cares? Use it to figure out which mics are out of phase then use your crossed mic cable(s) to effect the actual change of phase.

    Actually this seems like one of those little audio pals that Markertek and others carry. You might check with them first except they will be a lot more expensive. If you're handy with a soldering iron, you could do the thing for $10-15 bucks.

    Oh yeah, I just thought of another way. Buy a cheap audio transformer, 1:1 ratio (600 ohm to 600 ohm) like Edcor carries. You could even put a toggle switch on the output side to test phase polarity.
     
  3. dgooder

    dgooder Guest

    Hi Mike,

    There are plenty of tools available to check the polarity of mic cables and mics, but I think you are asking about the phase relationship between two mics in a particular position/situation. If you are sure all of your gear is technically "in phase," your ears should be able to identify any problems with your mic positions. Looking at the phase relationship on a scope (and knowing what you are looking at)can "teach" your ears what is considered unacceptable (as can summing to mono and listening to what disappears).


    Please disregard if you already knew this.....

    Dave g http://www.groovestainproductions.com
    570-839-1019 570-350-3422
     
  4. hargerst

    hargerst Active Member

    Joined:
    Jan 28, 2001
    The last part of Dave's answer is really good advice. Put the faders up on the two mics under test, hold them side by side, and see if they add or cancel. You can make a simple in-line polarity switch (with a DPDT switch) to reverse pins 2 and 3 if your board doesn't have one.
     
  5. Mixerman

    Mixerman Active Member

    Joined:
    Feb 27, 2001
    Yeah, but sometimes I like to check phase between mics even when their doesn't seem to be a phase cancellation problem. Particularly when summing mics, like 2 kick drum mic's.

    Sometimes we are dealing with subtler amounts of phase cohesion then 180 degrees, and the swap of phase can be desireable to how the mics combine to make a sound.

    Mixerman
     
  6. hargerst

    hargerst Active Member

    Joined:
    Jan 28, 2001
    Ahhh, I misread the question. I would be screwed without a polarity reverse switch on each channel of the board, but the switch thingy would do it.
     
  7. Instead of using your polarity-swapping mic cable, wire this into a short insert cable. This would make it a lot simpler on a Mackie.
     
  8. bluebass

    bluebass Guest

    Originally posted by The Kooch:
    Instead of using your polarity-swapping mic cable, wire this into a short insert cable. This would make it a lot simpler on a Mackie.

    Considering that the Mackie insert points are unbalanced, also mentioned by someone earlier in the thread, I'm a little confused (not unusual for me! :) ) as to how this would work?

    Is there a way to do this on a two conductor connection?

    Out from under the snow on Long Island :(

    Tim L
     
  9. Ang1970

    Ang1970 Well-Known Member

    Joined:
    Sep 5, 2000
    You can make one polarity inverted 1/4" TRS cable to feed from a bus or aux output back to an open channel on the mackie. Then "float" the channel in question (turn off L-R send) and feed it into the bus/aux so it comes back at the same level. You can A/B the reversed signal by alternating the L-R send on both channels. This will allow you to repeat the procedure quickly on a number of channels without repatching.
     
  10. mrivers

    mrivers Guest

    Originally posted by mike swanson:
    What is the quickest way to check phase on a couple of mics (eg. drumset) on a mixer without a phase button?

    Assuming the mics are in place, simply pan both to the same place in the L/R mix, and start with one fader up and the other one down. Then bring up the second fader while the drummer's pounding away. If the sound starts to get thinner, you need to fix something. If it just gets louder, and hopefully fuller, then they're OK. If it just gets louder but timbre and detail don't change in a good way, you probalby need only one mic for that purpose. Pick the one that sounds best and dump the other.

    Even cooler is to pick up a neat old oscilloscope, hang it on your L/R bus, and watch for out-of-phase infomration as you add mics to the mix. $25-50 at your neighborhood hamfest will get you a rack mount H-P or Tektronix, complete with toobs.
     
  11. swansonic

    swansonic Guest

    Thanks to all replies.
    I should have been a little more clear on my original post (next time). Mixerman nailed what I really was trying to say, and I will be building Harvey's dpdt switchy thing, and have taken steps for looking at old oscilloscopes (Mike Rivers).
    Thanks again.

    Mike Swanson
     

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