Speaker placement HT vs. Stereo

Discussion in 'Speakers' started by Mark Hedges, Apr 14, 2003.

  1. Mark Hedges

    Mark Hedges Second Unit

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    I am wondering if it is possible to have the same speaker placement be optimal for home theater and for stereo applications. It seems to me that to get the best HT sound the front mains would have to be farther apart than what would be best for stereo listening. Am I correct in this thought? What do you guys do who use the same setup for stereo and HT?

    Thanks!

    Mark
     
  2. Phil Iturralde

    Phil Iturralde Screenwriter

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    The following is from Dolby Labs website ...

     
  3. Mark Hedges

    Mark Hedges Second Unit

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    Thanks! That is a very usefull webpage. I am not clear though if, when they say "listening to music" they mean listening in surround (DPLII etc.) mode or if they are referring to good old 2 channel stereo. Maybe I will email Dolby and ask them.

    Mark
     
  4. Phil Iturralde

    Phil Iturralde Screenwriter

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  5. Bob McElfresh

    Bob McElfresh Producer

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    The goal of a lot of 2-channel music systems is to create a "image" between the 2 front speakers.

    This is typically done by adjusting the angle/toe-in of the L/R speakers so the soundfield intersects IN FRONT of the primary listening position.

    A simple laser pen is a nice tool to use. Just hold the pen along the outside speaker cabinent to see where the speaker is pointing. The classic music system has the 2 speakers intersecting 1-2 feet in front of the listener. Many magazine reviewers still do this when evaluating HT speakers so this alignment is not considered bad for HT.

    Hint: Roll the laser pen on a flat table while watching the beam on the wall across the room. If the beam moves back and forth - the beam is aligned with the pen body. If the beam makes circles as you roll, it's not aligned and you should look for another one. Try to get the longer pen-style laser pointers instead of the small "bullet" shaped units. You can also buy a "Laser Level" at hardware stores to be sure the beam is aligned with the level.

    Room to breathe

    There is another speaker issue that is often forgotten with HT systems: Speakers sound better with 2-3 feet of room around them.

    Instead of worrying about 40/60/80 degrees, try following the "Rule of Thirds":

    Pull your L/R speaker 1/3 of the way into the room, and then place them at 1/3 and 2/3 positions along the wall.

    Speakers DO radiate a lot of sound at 90 degrees to the face, and out the back. Giving space around them (and giving some toe-in) helps reduce early-reflections. And if you can get some delayed-reflections by having the speakers away from walls, you can give a room a much larger sense of space. This can create what is known as the "Hass Effect" which fools your ears into thinking the sound-source is several feet farther away than it really is.

    There is also the "Circle Theory" of speaker placment:

    Position your center speaker and measure the distance from your head at the listening position to the tweeter on the center speaker. Using this distance, draw an imaginary circle in front of you. Pull your L/R speakers forward and place them somewhere along this circle. The best position is one which gives the most breathing room/space around the L/R speakers. Now do the toe-in.

    IMPORTANT: Use 2-channel MUSIC to test/judge each speaker placement (since that is what you are trying to optimize for). But before fireing up a DVD, make sure to use a SPL meter to level-adjust the speakers. If you dont remember to do this, you may reject a great setup just because the levels are out-of-sync.

    Hope this helps.
     
  6. Mark Hedges

    Mark Hedges Second Unit

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    I will use your tips to adjust the toe-in. Unfortunately due to room setup issues I cannot move the speakers in from the wall. They are currently on a tv stand giving me an angle of about 30 degrees. I am going to get some bookcases and put them in it, which will allow me to increase the angle to 45 degrees or so.

    I get the impression it isn't really desireable to put speakers in a bookcase but since they have no ports (they are JBL S36II's) I figure it shouldn't hurt too much. It is my hope that any losses incured by placing them in the bookcases should be regained by increasing the separation and raising the tweeter to ear level (the tweeter is currently only 22" or so off the ground).

    Mark
     
  7. Phil Iturralde

    Phil Iturralde Screenwriter

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