Can I run two front centers from one output?

Discussion in 'AV Receivers' started by Kevin Lundberg, Feb 9, 2004.

  1. Kevin Lundberg

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    Soon I will purchase the Anthem PVA-7 multi-channel amp. I want to power two front center speakers. One top center and one bottom center. Both speakers will be B&W CC6 S2. Is this possible as I'm trying to fill the center channel sound gap. Thanks a bunch.
     
  2. JackS

    JackS Supporting Actor

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    Kevin- I don't think this is a good idea. Unless you've already heard a setup with two centers and appreciate the difference, then maybe. Never tried this but have read negative comments from others. If you have the amp and already own an extra center, no harm experimenting.
     
  3. Luitz

    Luitz Stunt Coordinator

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    Yes you can run 2 centers wire them up so your amp see's 16ohm's. Works sweet although You may need to recalabrate the reciever after so all sound lvl's match.
     
  4. Keith Mickunas

    Keith Mickunas Cinematographer

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    This is generally frowned upon because it can introduce nasty side effects such as cancellation.

    If you want to do it, there are two ways to go about it, you can either wire them in parallel or serial. I forget which is which, but one doubles the load on the amp, the other halves it. Do some searching on the web and you should find some info on it.
     
  5. Luitz

    Luitz Stunt Coordinator

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    That will only happen if your miss match your center channel.
    Seriously its work completely fine. There is no cancelation at all if they are matching.
     
  6. Keith Mickunas

    Keith Mickunas Cinematographer

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    Are you sure Luitz? My understanding is that two sound waves that are the same will cancel each other out if they meet properly. This means two speakers playing the exact same sound can cancel each other out. Every article I've read where people discuss two centers considers it to be a bad idea.
     
  7. Lew Crippen

    Lew Crippen Executive Producer

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    Not at all to criticize, Kevin, I just trying to figure out what you mean by ‘sound gap’. If your speakers are properly calibrated and you have a quality center speaker, you should have no trouble with volume from the center channel or with distinguishing dialogue. And if the center speaker is not up to the task of matching your other speakers, you might think about another model. And that center channel ought to be able to keep up with matching main and surround speakers.

    So I’m guessing that you mean something else—I’m just not sure what.
     
  8. Kevin Lundberg

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    Okay, Here's the deal. My center speaker currently sits on top of my 55" big screen. That places the speaker 30" above listening level. I have the speaker pointed down about 15 degrees but I feel there is a gap from below. My wife can not hear this gap but I'm a purist. I want to place another speaker at 30" below listening level pointed 15 degrees up to fill the gap from the bottom.

    Keep in mind as well that specific sounds come from the center channel and yes dialog is one of them. Specific sounds that the other speakers are not capable of due to the processor.

    If I had a small screen this sound gap would not be noticed.
     
  9. John S

    John S Producer

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    I run two, and have for years now....

    It works great, there are chances for cancellation, from phase, but I have found it a non issue.

    I use two JBL S38's by the way.
     
  10. Kevin Lundberg

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    In other words, dialog is coming from "slightly top" center. Not "center" center. I know of no other way to balance this out.
     
  11. John S

    John S Producer

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    Dang you must be a purist if you can really tell directionally that it is come'n from top center, and not center/center, as opposed to bottom center.

    Please come back and give your impressions after you add it.
    I was / am a recording and live sound engineer. Your good.
    I thought I was good, but your better.

    Ever thought of getting into studio and/or live sound re-enforcement? I'll bet you would be great at it.

    I actually use one on each side of the screen these days, I used to set them on top, but I felt it was to much weight for my new HDTV.
     
  12. Luitz

    Luitz Stunt Coordinator

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    Cancelation will only occure if you mix a speaker.
    Like a bookshelf with a 5 inch driver and a different one with a 4 or 6 inch and there side by side. Or your wire out of phase Then yes it could happen.
    As for laying a speaker cabneit down on its side or turning it upside down IMO doesnt matter.
     
  13. David Judah

    David Judah Screenwriter

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    series doubles
    parallel halves

    In theory it isn't a good idea, but in practice, as with many things in this hobby, it might not make much difference, as John can attest. I'd try it because you never know--every set-up is different.

    DJ
     
  14. Wayne A. Pflughaupt

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    The “canceling” thing has more to do with low frequencies – it’s more of an issue if you’re using multiple subs.

    However, if two matching speakers are placed side-by-side, there can be some comb filtering. So it’s probably best to separate them if you do use two. But then, you have the time-alignment problem when you’re off-axis.

    Regards,
    Wayne A. Pflughaupt
     
  15. AndrewErickson

    AndrewErickson Stunt Coordinator

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    This seems like a really bad idea to me. If you have a bottom center and top center, there are positions where the sound waves are 180 degrees out of phase and they will cancel each other. I would be sure that the distance from each speaker to your head is exactly the same.

    If it was me, I'd just angle the center channel down so that the sound will hit you at ear level.
     
  16. Mike Fassler

    Mike Fassler Supporting Actor

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    it will work, just be darn sure you calibrate properly and you will be fine.
     
  17. Kevin Lundberg

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    Guys, In a perfect world it is possible to phase sound out. In the real world I think it's nearly impossible if one was to try to achieve this. If by chance the sound was phased out a VERY slight adjustment would make it just right. Really, has anyone really experienced this phenomena? Likely not but theoretically possible.
     

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