Is there a definitive answer concerning the phase setting on subwoofers???

Discussion in 'Archived Threads 2001-2004' started by MichaelO, Dec 16, 2001.

  1. MichaelO

    MichaelO Stunt Coordinator

    Joined:
    Mar 29, 2000
    Messages:
    134
    Likes Received:
    0
    Hello. I have done some searches on this topic here but I haven't found one definitive answer concerning the phase setting on subwoofers. How are you supposed to set it? By what sounds the best? Or by which is the louder setting?
    I have played around with my HSU VTF-2 all night and some this morning just to make sure I have it right. The sub has a Phase Invert button, not for sure which is considered 0 and which is considered 180 but the button will either be pushed in or out. I had it set to out but I was calibrating all my channels with VE again last night and I noticed that when I pushed the invert button in the LFE signal would increase by about 2 dB's according to my trusty ole Radio Shack SPL meter.
    I listened to a lot of movies and songs last night and this morning constantly switching from button in to button out just to see which I liked better. It seemed that some songs sounded better with the button in whil others offered something a bit different with the button out although the bass was always less with the button out. However, it just seemed that there were some freq. that had a different sound than if the button was in. Perhaps what I am hearing to be different is actually something being cancelled out, I just don't know.
    The only thing I know for sure is that my sub is louder with the phase button in rather than out. Should I just leave the button pushed in and call that the definitive phase setting for my setup??? In case it matters my sub is in the front of the room with my mains, it is sitting in the left corner of my room.
    Any help will be greatly appreciated.
    Thanks!
    Michael
     
  2. RichardH

    RichardH Supporting Actor

    Joined:
    Nov 28, 2000
    Messages:
    742
    Likes Received:
    0
    On your Hsu sub, I'm pretty sure "invert" is equivalent to saying 180 degrees, which is out of phase. So, the button out would be 0 degrees, or in phase, and the button in would be 180 degress, or out of phase.

    As to which setting to use, you want the louder one.
     
  3. MichaelO

    MichaelO Stunt Coordinator

    Joined:
    Mar 29, 2000
    Messages:
    134
    Likes Received:
    0
    Richard, thanks so much. That is kinda what I figured, that having the button pressed in would be out of phase or 180. I was confused because I read that if you have your sub in the front of the room with your mains then it should be set at 0. However, as I mentioned earlier I get more output with the sub pressed in, or in effect set to 180.
    Guess I just wanted to make sure I had it set right. I left it pressed in so I guess I'm good to go.
    Thanks again for the help!
     
  4. Kevin C Brown

    Kevin C Brown Producer

    Joined:
    Aug 3, 2000
    Messages:
    5,712
    Likes Received:
    0
    Once you do have the phase button set for the "loudest" response, make sure to go back and balance its level with the rest of your speakers. Either internal tone generator on your receiver/pre-pro, or with a test disc like Avia or Video Essential.
     
  5. MichaelO

    MichaelO Stunt Coordinator

    Joined:
    Mar 29, 2000
    Messages:
    134
    Likes Received:
    0
    Kevin, thanks for the reminder. I actually forgot about this at first but was soon reminded when I listened to some music CD's, had to knock the sub setting down a few notches.
    Thanks again.
     
  6. Paul Allen Keatley

    Paul Allen Keatley Auditioning

    Joined:
    Aug 17, 2001
    Messages:
    4
    Likes Received:
    0
    As others have posted the loudest is the correct position.I believe this means the sub is not canceling the mains or vice versa. Many times this can only be checked with a SPL meter. You might also try a test with the balance control turned completly over to the side of the main front speaker that is closest to the sub.
     
  7. Tim Kilbride

    Tim Kilbride Stunt Coordinator

    Joined:
    Oct 6, 2001
    Messages:
    217
    Likes Received:
    0
    The setting of the switch is not relevant...there is a lot of things between the output you use for the sub and the speaker outputs to the driver in the sub. The best way is to get a phase checker (you may be able to rent one for a day from a pro audio shop locally). Some amps invert the signal, some don't...cabling could be also be an issue. Video Essentials also has a fairly good phase checking track.

    Tim Kilbride
     
  8. Jeremy Anderson

    Jeremy Anderson Screenwriter

    Joined:
    Nov 23, 1999
    Messages:
    1,049
    Likes Received:
    0
    Setting it to the loudest setting isn't necessarily the proper setting, and in fact can sometimes be the incorrect setting if the room acoustics are accentuating frequencies below the crossover range. The goal is to use the setting on the sub which is closest in phase to the speakers. For most applications, the 0 degree setting is fine. However, room acoustics can essentially invert the waveform. There are several ways to check subwoofer phase, but here are the two easiest:

    1) To check the phase, you have to have a disc which plays the subwoofer tone in one of the main channels, NOT the LFE channel (since it does not go to both the mains and the sub). Avia's tone for phase testing does just this -- it plays noise that spans across the crossover range so that bass management sends the tone to both the sub and speaker (with all speakers set to small). Then, while this noise is playing, you have someone flip the phase switch while you listen to the tone of the noise. The proper setting will bring out the upper and mid bass a bit more, since the speaker and the sub are reinforcing each other in the crossover range instead of cancelling each other out. It should be fairly obvious which is the proper setting.

    2) If you have a disc which does frequency sweeps, you can also easily check subwoofer phase. Run the frequency sweep while holding an SPL meter. Pay attention to the average SPL in the crossover range (commonly around 80Hz). Then have someone flip the sub's phase switch and run the frequency sweep again. The proper phase setting will show an obviously higher SPL in the crossover range (again, since the speaker and sub are reinforcing each other).

    After you've got the phase adjusted properly, calibrate your sub's level and you're good to go!
     
  9. Richard_Wg

    Richard_Wg Extra

    Joined:
    Dec 5, 2001
    Messages:
    15
    Likes Received:
    0
    Just wondering, if your subwoofer doesn't have a phase switch and you're using the lfe-out from the receiver; how do you correct it's phase?
     
  10. Allan Jayne

    Allan Jayne Cinematographer

    Joined:
    Nov 1, 1998
    Messages:
    2,404
    Likes Received:
    0
    When doing speaker phasing, I have always simply played a continuous low frequency tone, say between 50 and 80 Hz, on one speaker, then turn on another speaker and swapped the two wires going to just it for the louder sound. For a third speaker, I turn off one of the other two, and repeat the procedure, and so on.
    If the room is large, the speakers may seem to be in phase or out of phase depending on where in the room you are sitting and the exact frequency of the test tone. I have generally done the phasing test while standing exactly in between the two speakers.
    Occasionally the electronics may cause a partial phase shift (about 90 degrees) so one or more speakers are not fully in phase no matter which way you connect the wires. Also occasionally the source material is not in phase so you cannot rely on just one passage from one CD or DVD for testing.
    Video hints:
    http://members.aol.com/ajaynejr/video.htm
     
  11. MichaelO

    MichaelO Stunt Coordinator

    Joined:
    Mar 29, 2000
    Messages:
    134
    Likes Received:
    0
    Thanks for all the great advice. I thought I had it all wrapped up, looks like I have a little bit more work ahead of me.
    Again, thanks for all the help, I really appreciate it!
    Michael
     
  12. RichardH

    RichardH Supporting Actor

    Joined:
    Nov 28, 2000
    Messages:
    742
    Likes Received:
    0
    Richard_wg:

    You could simply reverse the + and - leads from the amp to the speaker. Easy to do if you have an outboard amp, a little more involved if you have a typical powered sub.

    Of course, this makes A/B testing harder, but you can run something, record SPL levels, reverse the leads, and run it again at the same volume.
     

Share This Page