Does this center channel layout have some advantage?

Discussion in 'Archived Threads 2001-2004' started by Dustin B, May 31, 2002.

  1. Dustin B

    Dustin B Producer

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    Axiom is becoming quite popular in the speakers section. Their subs look quite pathetic. The bookshelves and towers look good. There two lower model centers look like standard fair for the price range. But their top center vexes me. My enough knowledge to be dangerous tells me this layout is a bad idea. Is there some advantage to sticking a pair of tweeters on the sides like they did?
    http://www.axiomaudio.com/vp150.html
     
  2. ThomasW

    ThomasW Cinematographer

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    I would avoid that layout like the plague!

    IMO the best center channel design is a MTM with side flanking woofers.
     
  3. Brian Bunge

    Brian Bunge Producer

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    Dustin,

    I think I read in one thread that the tweeters to the sides are supposed to reduce the off axis suckout (to what level I'm not sure). I remember responding that while it may take care of some of the problems that there is still the issue of ceiling and floor reflections from a horizontally oriented speaker.

    I'm interested in the real experts' input as well.

    Brian

    P.S. Remember I built an almost identical sub to theirs? I think it could mate well with some little full range drivers for a Bose-Buster system. But for what they're charging for them I'd agree that they're pathetic. They don't even use 3/4" MDF!
     
  4. Dustin B

    Dustin B Producer

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    My reading would have me thinking it would make off axis performance worse. I remember a bunch of threads saying the problem with 2 way MTM horizontal centers is that if the crossover to the mid/woofs is two high the distance between them can cause some really bad off axis effects. Like a full wave length or more from one mid/woof will arrive before the first sound from the second one. That center has two tweeters over a foot and half appart. Wouldn't this layout make the 2way MTM problem many times worse?
     
  5. ThomasW

    ThomasW Cinematographer

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  6. Brian Bunge

    Brian Bunge Producer

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    Thomas,

    Well, you and Greg Monfort were the two main guys I was thinking of when I posted (and of course John but he isn't around here too much)! You and I just happened to be responding to Dustin about the same time.

    Dustin,

    IIRC, the issue is the CTC spacing of the woofers in an MTM design and then lying it on it's side. I don't see how adding tweeters to the outside accomplishes much either.

    Brian
     
  7. Ron-P

    Ron-P Producer

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    Ron
    Freq Resp+/-3db (Hz) 50-22K
    Woofer ~ Triple 5.25"
    What a weak center. I'd aviod this like the plague just from these alone.
    Peace Out~[​IMG]
     
  8. Brian Bunge

    Brian Bunge Producer

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    Ron,
    And don't forget the cheap cabinet materials! [​IMG]
    Brian
     
  9. Ron D Core

    Ron D Core Stunt Coordinator

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    If the MTM setup is set sideways, then should a ribbon tweeter sit sideways too?
     
  10. ThomasW

    ThomasW Cinematographer

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  11. Michael R Price

    Michael R Price Screenwriter

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    So Thomas, doesn't the 2-way MTM create lobing cancellations off-axis? I'd think it would be better to do a 2.5 or 3 way system for a center with more than one woofer.
     
  12. Dustin B

    Dustin B Producer

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    That's the term I was trying to remember. Wouldn't the tweeters on the sides create horrible off axis lobing?
     
  13. ThomasW

    ThomasW Cinematographer

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    Micheal

    If you want someone to debate the Konar vs D'Appolito view of MTM lobing, head over to the Audio Asylum. They're always up for a good spat.

    Cheers
    Thomas
     
  14. Greg Monfort

    Greg Monfort Supporting Actor

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    Well, when this 'expert' (and I use the term loosely) sees a design that at a glance is so contrary/ridiculous to what he thinks he knows, he starts wondering what they know that he doesn't, especially in this case where he's wondering how they can tweak it to sound good enough in an A/B/C, etc., comparison test to close a sale. Companies generally don't waste time on a product that they know before hand just flat won't work.

    Based solely on tweeter placement, they're so far apart that off axis comb filtering exists over (probably) all of their BW, and since these are (I assume) two discrete mono signals could vary from obvious off axis echo to audible cancellation of one tweeter's output.

    I'm guessing the XO point/physical placement is designed for audible cancellation, similar to what happens with the multicell (~constant directivity) theater horns of yesteryear, or it may be a variation of Bessel alignment.

    Another thing to consider is how much our vision plays in our hearing of a visual event, such as watching a movie, and they may be counting on that some too.

    Anywho, knowing that the multicell (or multiple driver array) concept of lobing works well in the upper mids/HF of a mono channel (after all, it was the cinema standard for >50yrs), I can't help but wonder if they haven't just developed a variant. Maybe they're dumb like a Fox (or B***).

    WRT the Konar vs D'Appolito view of MTM lobing, a high res TDS plot tells the tale doesn't it, so what's to debate?

    GM
     

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