What's phase?

Discussion in 'Speakers & Subwoofers' started by itai, Feb 25, 2004.

  1. itai

    itai Stunt Coordinator

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    Hi all
    I hear (read...) people talking about a phase feature in their subs (my audiopro subevidence sub hasnt got one), and about dialing/blending it in.
    What's getting blended? isnt that the crossover's job?
    Thanks![​IMG]
     
  2. John Garcia

    John Garcia Executive Producer

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    Blended meaning, in phase with the main/other speakers. Phase would refer to the movement of the cones relative to each speaker. If you hooked the R speaker with + and - one way, and the L speaker the opposite, they would be out of phase. Being out of phase, the drivers would move in and out at opposite times (180 out of phase), and is likely to cause cancellation of certain frequencies. A sub can do this as well, and placement within the room will affect this.
     
  3. itai

    itai Stunt Coordinator

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    Thanks!
     
  4. Keith Hyde

    Keith Hyde Stunt Coordinator

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    Speaking of... any good way to dial in your phase adjustment on a PB2+ - by yourself? I "think" I have it where it sounds best.
     
  5. TimRP

    TimRP Stunt Coordinator

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    Play a tone that is equal to the crossover frequency usally 80hz, then have someone dial the phase control until your sound level meter at your main listening position reads the loudest.
     
  6. Wayne A. Pflughaupt

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    No. That is polarity. Phase has to do with delay or time alingnment.

    Regards,
    Wayne A. Pflughaupt
     
  7. Ron Sc

    Ron Sc Agent

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    Exactly.
     
  8. John Garcia

    John Garcia Executive Producer

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    Yes, it is polarity, but the result would be speakers 180 out of phase, right? Time alignment should not be an issue in most HTs, since the distances are not great enough. In a proper setup, as you often point out, you should have your speakers as nearly equidistant as possible as well.

    Most subs only have 0 or 180, which is little more than a switch that swaps polarity at the driver, AFAIK, since if you are using a line level out, there are no wires to swap. I've never tried to calibrate a sub with an infinitely variable phase switch. It is my understanding that phase is included with a sub because you are more likely to have cancellation where the sub and mains overlap, depending on the x-over slopes and the sub's placement relative to the mains. Certain overlapped frequencies may have an out of phase relationship, causing cancellation. The question was regarding the phase switch on subs.
     

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