Subwoofer phase correction

Discussion in 'Subwoofers' started by rushtemples, Apr 24, 2016.

  1. rushtemples

    rushtemples
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    My basement theater set up has two subs. I currently have them both at the front of the room, I know not the best but most practical for my particular room. A deftech super cube 8000 and a smaller super cube III. Since they are both at the front of the room is this a situation where setting the phase on one of the subs to 180 degrees could be helpful to decrease bass frequency holes and hills?
     
  2. Bbos37

    Bbos37
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    No nesesaryl you'll need a spl meter to check weather your subs are in proper phase.
    With a spl meter measure a single sub and the the reading, now measure both the sub there should be an increase of 3 to 5 dB.Than your sub is in phase.
     
  3. rushtemples

    rushtemples
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    Would I take readings from multiple places in my room or just from sweet spot? I'm looking to get the best experience for everyone in the room.
     
  4. BlueWizard

    BlueWizard
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    If both are placed at the front of the room, then they are both In-Phase.

    However, as the most obvious example, if one is placed at the front of the room and the other is placed at the back of the room, they are OUT of Phase. When the Front Subwoofer moves North, the Back Subwoofer moves South, making them 180° out of phase.

    Though the above assumes Front Firing Subwoofers. If they are Down Firing, I think it might be less of a problem when we consider the Diaphragms or the cones. But if we consider the movement of the created Wave Front, they are still going to oppose each other. If the front is at 0° Phase and the rear is at 180° Phase, then the movement of the air is going to be synchronized. Though I speculate that the effect is going to be less pronounced with Down Firing Subwoofer.

    Though there is an element of circumstances and personal taste involved.

    If one Sub is at the Front and one is at the Side, then the Phase becomes more unclear. If you options are 0° and 180°, then you just have to try and see which works best.

    If you have a variable Phase Control that goes from 0° to 180° in a continuous sweep, then you again need to experiment to find the Phase of the Side Sub that best compliments the Front Sub.

    As to your current setup, as others have said, the speaker should be in-phase, but you are free to experiment to see if another combination suits your personal taste better. Though again, logically, both being at the Front, they should be in phase.

    As someone else said, when the two Sub compliment each other, you should get an increases in the perceived output, and when they are opposing each other, a slight drop in the output. But the change should certainly be enough to be noticeable.

    Steve/bluewizard
     
    Last edited: May 27, 2016
  5. rushtemples

    rushtemples
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    I do get a db bump with the second sub added to front of the room, but I do think I need to experiment moving the smaller sub around the room as the bass in the room seems too uneven in some seats.
     
  6. BlueWizard

    BlueWizard
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    The advantage of having more than one Sub is more even distribution of bass sound in the room. Each will fill the areas that the other doesn't cover. However, to work right placement is somewhat critical to make sure the Sub compliment each other.

    So, like to do what is called the Sub Crawl. You place the Sub in or near the Prime Seating position while you move yourself around the room, both horizontally and vertically, until you find a spot where the Bass sounds best. That's the spot where you then place the Sub.

    As to the dB boost, once you have both Subs in a position you like, run the Setup program again, and it will balance the output of the Subs with the rest of the speakers. Though you do have some option to adjust it to tasted. But let the Setup program make the initial adjustment. Then you can tweak it a bit if you so desire.

    Steve/bluewizard
     
  7. rushtemples

    rushtemples
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    That clears up my next question! I have heard explanations of the sub crawl but still didn't really get it till now. I think I would move the smaller of the two subs and leave the larger in the front. I assume I should turn off one sub and do one at a time?
     
  8. Deleted member 598831

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    If running an avr the issue of phase, can be dealt with in the time delay on the distance settings.

    To obtain a far more detailed response post this in the subwoofers section @DodgeTheViper
     
  9. droidlike

    droidlike
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    Question - Setting up a SVS Ultra PC 13

    >>5. Phase degree? How do you decide what degree you set it at ?
    >> Do you play a bass test tone and then with SPL set it at the highest reading on the SPL?

    I started here

    Press Reviews & Awards | Best Speakers & Subwoofers – tagged "SB13-Ultra" – SVS

    and found out this one in a minute or so

    The Poor Audiophile: SVS SB13-Ultra Subwoofer Review
    .
    .
    .
    Getting the phase correct on a subwoofer is important an easy to do. If you don’t know how to set a subwoofer’s phase, here’s a primer:
    1. Play pink noise from your receiver or play static from an FM station.
    2. From your listening position, measure the sound output using an SPL (sound pressure level) meter that is set to C-weighted and slow. If you don’t have an SPL meter, order the $35 analog meter from Radio Shack.
    3. Whichever phase setting produces the loudest SPL reading is the correct phase.
    I tested the phase of each subwoofer with my Anthem AVM50v’s system-generated Pink Noise. Unsurprisingly setting the phase to zero provided the loudest SPL setting. (Tip: If you don’t have an SPL meter and are placing the subwoofers at the front of the room and near the same plane as your main speakers, then you can safely set zero as the phase).

    ?
     
  10. Bbos37

    Bbos37
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    Take reading from the MLP.
     

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