my little line array project

Discussion in 'Home Theater Projects' started by Matt Dolejsi, Sep 18, 2003.

  1. Matt Dolejsi

    Matt Dolejsi Agent

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    Hi, I'm just looking for any advice having to do with my current project...

    I bought sixteen 4" drivers (couple bucks a piece) to put in a line array configuration that i'll probably end up using as my center channel if it all works out ok. Fs of about 105 which is not too too bad, I can get the over all Q very close to .707 be it that it is a little higher, but with some EQ and stuffing it should be fine i think.

    Of course there's only 1mm xmax but frequency response is quite extended and having 201 in^2 of cone area should help with some bass output.

    Any advice, thumbs up, or criticism is welcome...
     
  2. Matt Dolejsi

    Matt Dolejsi Agent

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    should i bother with an xover? i'll probably make two 16 ohm groups and biwire to my denon
     
  3. TimForman

    TimForman Supporting Actor

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    I'd suggest reading Jim Griffin's white paper on line arrays. Also, since you mentioned possibly using it as a center channel, remember that the sound field from an array is cylindrical and when layed on it's side may suffer from a narrow sound field unless you're using all 16 in one enclosure (pretty big cc). If it's vertical it will work great but placement could be a challenge.
     
  4. Brian Bunge

    Brian Bunge Producer

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    Also, high frequency response will suffer from comb filtering. Assuming the drivers are slightly over 4" in diameter and are spaced frame to frame, this will start somewhere in the area of 3200-3300Hz.
     
  5. Matt Dolejsi

    Matt Dolejsi Agent

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    i was thinking 2 groups of eight, one on either side of the television, so they would be vertical, not standard by any means but it could be interesting especially since i move around alot when i listen and its mostly music. How bad will the comb filtering effect be, can i do anything to alleviate it...
     
  6. Chuck Bogie

    Chuck Bogie Second Unit

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    You know, that is a thought - _can_ dual center channels work?
     
  7. TimForman

    TimForman Supporting Actor

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    Sure, why not?
     
  8. Denis P

    Denis P Extra

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    Two center channels is not a good idea because you will get cancelation effects unless the listener is exactly centered between the speakers. If you are off to one side, even a little, the difference in arrival time will cause some band of frequencies (frequency dependent on difference in speaker distance from listenner) to arrive out of phase with the other speaker. It's the equivalent of comb effect but in the horizontal plane and with much greater speaker separation.
     
  9. TimForman

    TimForman Supporting Actor

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    That's a good point Denis. Based on my trial-and-error at a center channel it doesn't surprise me. I'm modifying my design now. As to comb-effect from arrays I believe that occurs in the very near field (1m) and diminishes as the listening distance is increased.
     
  10. Jim Griffin

    Jim Griffin Extra

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    Tim,

    When you begin to have comb line effects what you would observe is that the sensitivity of the array decreases (loss of directivity) for higher frequencies. You may also detect off axis artifacts as you walk around the room with the right material. Now with an untrained listener and material that does include a lot of highs, then you may not notice the effects. Part of this is because the ear is less sensitive in the 10-20 kHz octave.

    Jim
     

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