Setting the sub woofer phase control

Discussion in 'Archived Threads 2001-2004' started by GarryW, Sep 18, 2002.

  1. GarryW

    GarryW Stunt Coordinator

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    In reading Robert Harleys book on High End Audio, he states and excellent way for those of us that have a dial adjustment for phase adjustment on your sub. (I belive this will also work for those that have a toggle switch adjustment too). This adjustment is usually between 0° and 180°. The aim is to make sure that the woofers in your mains are in phase with the sub and not working against one another whch casues cancelleation of the bass frequencies. Here you go:
    Swap the speaker leads on your mains (the +(red) and - (black). Play a test tone thru your CD player equal to the point where you have your subwoofer cutoff set at, usually 80 Hz.
    Then have an assistant turn the phase control knob on you sub to the point where your mains are generating the LEAST amount of bass. When you reach this point, stop and your done!
    Then reconnect your main speaker leads as before, and you will have everything in proper phase. You should only need to do this once, unless you move or change you set up.
    I highly recommend this book! [​IMG] Lots of great tips if your a newbie or an audiophile.
     
  2. John Desmond

    John Desmond Stunt Coordinator

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    Yep, that will work. OR, even easier. DON"T swap the leads on your mains. Just adjust the phase until you have the MAX bass output at the crossover frequency. Same thing, one less step[​IMG]
     
  3. Arron H

    Arron H Second Unit

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    John,

    So if I am understanding you correctly, you would play the crossover tone (for example, 80Hz), measure the output of the mains/sub at 80Hz from the listening position, and adjust the phase to where maximum bass output from the mains/sub is reached at 80Hz?
     
  4. KennethO

    KennethO Auditioning

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    John,

    True, but most people will be able to sense minimums better than maximums. True for light, sound, etc.
     
  5. GarryW

    GarryW Stunt Coordinator

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    It's true that you can do it the way John suggests, but it is more difficult to get it right. Most sbwoofer manuals do recommend it that way. I was going to post that as the "usual way" but if you try Harley's method, IMO, you'll probably see better results.[​IMG]
     
  6. John Desmond

    John Desmond Stunt Coordinator

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    I think you can do it either way with pretty much the same results. It is true that many people are better able to sense the minimum output than the max output. I think I'm just the opposite on this, then again, some of my friend's say I'm sort of backward[​IMG]
    If you use a meter, either way will certainly work the same.
     
  7. aldamon

    aldamon Second Unit

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    I have my sub corner loaded and saw and heard no difference between 0 and 180. I've left it at 0 until I can make some sense of this.
     
  8. David Berry

    David Berry Stunt Coordinator

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    Garry,

    Right on about that book! I bought it about 3 weeks ago and am now into my second reading of it. A lot of knowledge and useful tips for the $55 Cdn. invested.
     
  9. GarryW

    GarryW Stunt Coordinator

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    For others who maybe interested in picking up a copy of the Harleys book, you can get it at www.amazon.com for $19.95 + shipping.
    Dave, did you get the hard cover? $55 Canuck seems like a lot, but still worth it![​IMG]
     
  10. David Berry

    David Berry Stunt Coordinator

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    Yes indeed I did get it in hard cover. I know myself well enough that over the years, I will re-read it many times and I wanted it to last. I don't like picking up flopsy soft cover books.
    I bought mine here. The $55 Cdn. was the total cost.
     
  11. Arron H

    Arron H Second Unit

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    I followed John's recommendation and ended up making a slight adjustment to the phase. Before, the phase was set at just past 12 o'clock. It is now at just past 11 o'clock. To be honest, my ears don't register much of a difference but it was interesting to watch the output dip a Db or so on either side of 11 o'clock.
     
  12. Craig Morris

    Craig Morris Stunt Coordinator

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    Revel does it the "max" way using their LFE test disc that comes with the B15. If you're using an 80Hz x-over, you play the 80Hz test tone running both the sub and your mains and adjust the phase until the combined output reads the highest on your sound meter.

    I have found that this works best with an assistant and that the measured output rarely varies more than 1-2dB on the meter (in my room anyways).
     
  13. Joe Szott

    Joe Szott Screenwriter

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    Just wondering, how do you generate an exact 80 Hz tone? Is there a test CD that comes with this book?

    Thanks,
    Joe
     
  14. GarryW

    GarryW Stunt Coordinator

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    Joe:

    There is no tet tone CD supplied with the book. There are test tones in the Avia DVD you can use, but maybe others can post where you can get a good Test Tone CD to accomplish this task.
     
  15. Will Orth

    Will Orth Stunt Coordinator

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    I hae messed with this PHASE switch on active X-OVERS for years and could not tell any differnce? I think it is there if you wire your speakers out of phase or have the drivers facing each other -- but no I have made -0- sence of this as well.



    Will
     
  16. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    I have a link to test tones/generators at my site
    Here's something:
    Sometimes you may not want to have the subs and mains play the loudest bass together. What happens when you're inside a room that has a spike near 80hz? In this case, changing the phase so that the subs and mains cancel eachother out a little at the listener position could be helpful for equalization.
    I believe the primary reason for phase control on a subwoofer is to adjust the "crossover" frequencies to overlap and match the main's lowest frequencies. It is a tool to adjust how loud you want your 80hz tone to be without having to adjust the level of all the other frequencies. (like with gain)
     

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