Speakers in phase? Will they grow out of it?

Discussion in 'Archived Threads 2001-2004' started by Christian Speights, Dec 15, 2001.

  1. Christian Speights

    Christian Speights Stunt Coordinator

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    In phase. Out of phase. I have seen it mentioned on TONS of other threads. Some of those threads even explained it.
    But I still don't understand. [​IMG]
    Can someone explain it to me like I'm a third grader?
    Thanks in advance.
     
  2. Glenn Overholt

    Glenn Overholt Producer

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    It's just doing a switch on the cables. The 'red' outlet on the receiver would be connected to the black socket on the speaker. They still work but the sound is off, or 'out of phase'.

    Glenn
     
  3. Christian Speights

    Christian Speights Stunt Coordinator

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    So how does that apply to a subwoofer?
    There's no positive and negative connections for the sub out on my receiver.I can't reverse the polarity.
    [​IMG]
     
  4. ThomasW

    ThomasW Cinematographer

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    Just like grade school.....

    The cone of the driver in the sub, and the cones of the drivers in the main speakers need to be moving in and out at the same time. That's called 'being in phase'.

    To check phase just listen to a CD/DVD that has deep bass. Reverse the leads to the sub. If there's less bass, the drivers were already in phase. If you hear more bass they are now in phase.
     
  5. RichardH

    RichardH Supporting Actor

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    An audio wave consists of "compressions" and "rarefactions". The compressions are the part above the zero line reference. The rarefactions are the part below. Think of a sine wave. The swell up is the compression, the dip down is the rarefaction.

    If you have two sources of sound outputting the same thing, you'll want those sources to be in phase. That means, when one cone is pushing out (creating a compression), you'll want the other cone pushing out as well. If one is moving opposite of the other, you'll get cancellation from the two waves that are "out of phase".

    In practical terms, if you wired one speaker out of phase with another, most of the bass would disappear. Try it out and see, it won't hurt anything.

    On a subwoofer, they inlude a phase switch so you can electronically switch the phase. This is in case you don't have your sub close to your mains. e.g. if you had the sub at the back of the room, you'd likely want to flip the phase because depending on the length of the room, the waves could be arriving out of phase between the mains and the sub.

    Hope that helped.
     
  6. Bryan Acevedo

    Bryan Acevedo Second Unit

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    And some subs have continuosly variable phase controls. This is so that the sound waves arrive at your ear in phase.

    I think this is what he is talking about.

    If you have your subs and mains in different locations, then the sound waves (think of the sine waves) can get to your ears at different times. The timing (or the phase) could be off just slightly, so that the peak for the sub is just before the peak of the mains, or vice versa. This can lead to a cancellation of the overlapping bass, or can also lead to a "wierd" kind of sound. Maybe the bass doesn't seem as tight or clean. It could sound "slow" or disconnected.

    This is what they mean when they are talking about phase adjustments with respect to subs and mains. In my opinion, the 0 or 180 switch is useless, as it is usually not exactly in phase or out of phase, but somewhere in between. Chalk that up to marketing, as they want to be able to say they have a switch that everyone else has.

    Unless your speakers and subs are far apart, I would just leave it at 0, unless it sounds better at 180. But I would bet that it won't.

    Bryan
     
  7. Christian Speights

    Christian Speights Stunt Coordinator

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    Now that's what I'm talking about! [​IMG]
    Thanks for the great explanations. Now I am looking forward to fourth grade.
    [​IMG]
     
  8. BertFalasco

    BertFalasco Supporting Actor

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    Man, I was at my brother's friends shop and my bro. was showing his friend his show car and we discovered that Richard's (brother) system was out of phase. We lifted up the box "sheet" and we played some bassy shite and the woofers were going opposite, pretty weird looking (as one vibrated out the other vibrated in). Nothing a little rewiring couldn't fix.

    -Bert
     
  9. Kevin C Brown

    Kevin C Brown Producer

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    Be careful though.

    I have my sub in the left corner right behind my left main speaker. I have measured the distance to each of my speakers plus the sub and set that correctly in my pre/pro. You'd think I'd be able to set the phase at 0 and everything would be hunky dory, right?

    Nope. I have to dial in -120 deg to get it right. The phase difference between your mains and sub can also change based on how your receiver/pre-pro does the crossing over between them. Basically *any* filter applied to the mains and/or the sub can change phase. And even the internal crossover in your main speakers can affect the phase of its woofer in relationship to your sub.

    In other words, there are no "rules of thumb" concerning how to set the phase of your sub to match your mains. You either have to listen to music or test tones (under, at, and above the crossover pt), or measure with test tones.
     
  10. Rick_Brown

    Rick_Brown Second Unit

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    For the Front, Center and Rear speakers, the normal advice is to connect red terminal on the receiver to red terminal on the speaker, black to black, etc. But I never trust that the speakers are properly labeled or wired, so I check phase with a test DVD. I know that the possibility of mis-labeled or mis-wired speakers is remote, but it did happen to me years ago. I couldn't understand why my then stereo system sounded so lifeless - until a test showed that one speaker was incorrectly wired. The possibilities of this happening are increased with inexpensive speakers and DIY's.
     
  11. Chris PC

    Chris PC Producer

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    I can detect stereo speakers out of phase 99% of the time.
     
  12. John H

    John H Second Unit

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  13. Alan Wild

    Alan Wild Stunt Coordinator

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    I too have similiar gear and would also like some tips on the best way to adjust phase.... I don't care if the procedure is complicated.
    The best explanation I've ever heard was... Sit in the primary spot and have someone turn the dial. Leave it wherever the bass was loudest.
    I've thought trying to measure it with the SPL meter but is that the best way?
    -Alan
    Edit: To correct horribly broken engligh. [​IMG]
     

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