thx surround effect

Discussion in 'Speakers & Subwoofers' started by Simon Brooke, Nov 25, 2003.

  1. Simon Brooke

    Simon Brooke Stunt Coordinator

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    i just took a listen to the thx speaker setup on the AOTC DVD.

    even though i do not have an ex setup, when the test went to set the rear speakers it filled the area behind me with the sound coming from the side surrounds.

    how can i get this effect without having to go and upgrade to a 7.1 receiver?

    will dipoles do the trick?

    i really liked the effect
     
  2. ChrisWiggles

    ChrisWiggles Producer

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    this question is a little confusing.

    First, THX is not a sound format, but more a seal of approval that also comes with a few added features. See the beginner's primer and FAQ for an explanation that THX is not a sound format.

    Second, I'm confused as to where you heard the effect of sound behind you. Was this at a 7.1 demo at like a store? 5.1 should, if setup correctly, image behind you a little bit. The added speakers definitely help in this regard. If, as I intepret it, you heard this at home, I don't quite understand your question. You have a 5.1 setup, and you played the THX intro on ATOC, and sounds came from behind you, which is the way it's supposed to be.

    Perhaps you could elaborate a little...
     
  3. Robert AG

    Robert AG Stunt Coordinator

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    If an EX film is played in 5.1, the signal that would normally be reproduced by the rear surrounds in a 7.1 setup will come out of both the left and right side surrounds. This might sound like it is coming from behind the listener, depending on the room acoustics, the position of the listener, or possibly some DSP post processing in the receiver or pre/pro.
     
  4. Simon Brooke

    Simon Brooke Stunt Coordinator

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    sorry i think i misreprsented myself a bit. i have a 5.1 setup at home.

    i was using the thx optimiser, while it goes through the various speakers from front to center and and then to the surrounds.

    when it checked the right surrounds everthing was okay, it does check for surround back speakers though, which i don't have. anyway it sounded like it was coming from behind me and not from the sides.i don't get this effect when watching a dvd.

    i feel most of the time my surrounds feel a little localised which i tried to fix by turning them down a little bit. i have my surrounds using the recommened way on the dolby site.
     
  5. ChrisWiggles

    ChrisWiggles Producer

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    Gotcha.

    Ok, well, the only thing that EX/ES (Dolby digital EX, or DTS ES) processing does is take sounds that are equal in volume/equally split between L and R surrounds, and send that sound instead to a 6th channel and speaker(s). As you noted, when there are sounds that are supposed to come from behind you, they will sound like that, as they did in the THX test. Adding more speakers will help the rear imaging and ambience a bit, but it sounds like you already have a proper setup allowing the surrounds to image behind you properly, given the slight limitations of a 5.1 setup. In short, there is nothing you need to do, unless you fully move to a full 6.1/7.1 setup.

    So your question as to "how can i get this effect" is somewhat silly, because you ARE getting that effect as you pointed out in the thx demo, because it sounds like you have proper placement of your surrounds.
     

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