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in phase, out of phase...

Discussion in 'Speakers' started by William_Gravem, Jan 25, 2005.

  1. William_Gravem

    William_Gravem Stunt Coordinator

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    All,

    Last night I threw on a Star Wars DVD and tried the THX audio check. The first check was simply a test to make sure my speakers were in the right places, and my first question is simply, why doesn't my subwoofer make any noise when I do this? I encounter the same thing when I'm calibrating my system through the receiver.

    The second test was a phase test. It seemed to go through sets of speakers, and when it tested "in phase" I was supposed to hear the sound coming from between two given speakers, when it was "out of phase" it was supposed to sound like the sound was coming from an un-locatable source.

    When it tested the rears, the "in phase" sounded like it was coming from straight behind me, but the "out of phase" test tones seemed to make the sound vanish. Is this normal?

    Just an FYI, I have an Onkyo 601 receiver, 5.1 with Axiom speakers (M22, VP100, QS8) and an SVS PB12 sub. I also have a non-ideal layout. Condo with L-shaped living room, 6-box coffered ceiling, and the back of the room that the speakers face is 1/3rd wall, 1/3rd pass through into Kitchen, 1/3rd pass through into dining room.

    ---Bill
     
  2. John S

    John S Producer

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    Hmm I never tried the THX audio stuff. I may visit this in the next few evenings.
     
  3. Jeff Gatie

    Jeff Gatie Lead Actor

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    Wiiliam, It sounds like you may be listening to a Pro-Logic downmix of the DD stream. Since Pro-Logic only has mono surrounds that rely on phase shitfting to derive the surround channel and has no ".1" for the sub, the observation you describe leads me to think that you are listening to a downmix. Go into the setup for your DVD player (often only available when there is no disk in the player) and make sure the audio output is set to "Dolby Digital" or "Bitstream". Also, make sure your receiver is seeing "Dolby Digital" when you play a DD disk.
     
  4. Jeremy Anderson

    Jeremy Anderson Screenwriter

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    William, I have some bad news:
    The Onkyo TX-SR601 has a problem in 6.1 where the out of phase tone for the surrounds goes quiet instead of properly passing the signal to the left and right surrounds. To my knowledge, however, this only occurs with a 6.1 setup in EX/ES mode and should not occur with 5.1.

    The problem is that some 601's are basically throwing away out-of-phase sound in the surrounds during processing when EX/ES is engaged. Onkyo is aware of the issue (because I stayed on them for months to acknowledge it) and there were quite a few people who found that they had this issue. Unfortunately, the fix is for Onkyo to replace one of the chips in the unit, meaning you'd have to be without a receiver for a while if you want it fixed.

    Here's the caveat: People at both Onkyo and Dolby (who I consulted to find out if this was normal behavior for EX processing) say that while this isn't correct, you shouldn't notice much of a difference during movies. Respectfully, myself and many others heard a HUGE difference. Because I was the first to call their attention to this issue, they sent me a working model that they had already tested and I was able to A/B with my 601; there was definitely a difference, and the properly working receiver sounds MUCH better.

    So if it's really going to bother you, call Onkyo and have it replaced. Just be aware that some people were without their receivers for up to 2 months to have this issue fixed.
     

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