Question on back speakers for 6.1/7.1

Discussion in 'Archived Threads 2001-2004' started by DanielN, Nov 7, 2002.

  1. DanielN

    DanielN Stunt Coordinator

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    I keep reading that some 6.1 receivers like the Pioneer VSX-811S and maybe the Denon 1803 (not sure on that one) allow one to split the rear surround speaker into 2 for a 7.1 setup. Is this true and how does it accomplish this? Does it split the wattage between the 2 speakers? Does it half the resistance? Etc...

    Thanks in advance,
    Dan
     
  2. DanielN

    DanielN Stunt Coordinator

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    Ok, doing some research I think I answered my own question. If I want to split the rear channel on a 6.1 receiver I need to hook the 2 speakers in series or parallel. If I hook them in parallel it drops the impedance to 4 ohm. I guess the question is do most receivers today handle a 4 ohm impedance? Or am I asking for trouble by doing this.
     
  3. Kevin Deacon

    Kevin Deacon Second Unit

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    You need to add more channels of amplification for those extra rear speakers.
     
  4. ChrisWiggles

    ChrisWiggles Producer

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    That's a negative. As long as there are 6 amps, you can use two speakers on that rear channel. Series or parallel, I'm not too clear as to which would be preferable, it would seem to me that the end result would be the same in terms of load on the amp to get the same volume. Ideally, you'd wanna have two amps back there, but how much sound actually comes from way back there...not much.

    Perhaps someone will chime in on the parallel vs/ series connection?
     
  5. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    Some receivers, like the Pioneer VSX-D811S and the Denon 1803 have 6 amps, but also have 2 connections for the rear speakers. Other receivers, like the Panasonic HE100, HE200, and the Denon 2802 only have one connection for the rear speaker.

    The receivers that have 2 connections are essentially wiring the 2 speakers in series (when 2 speakers are present). If you plan to hook 2 speakers to a receiver that only has one connection, you should wire in series.

    There IS a BIG difference in wiring in parallel vs wiring in series. The difference is not as much an audible one as it is a difference in the load put on your amp.

    For example, wiring 2 8ohm speakers in parallel puts a 4ohm load on the amp. This is less resistance than it is designed for (due to the fact that there are now 2 paths for the current to travel). This can cause damage to your amps over time (through overloads and overheating).

    Wiring 2 8ohm speakers in series puts a 16ohm load on your amp. The higher resistance means that less current is flowing back to the amp, and is therefore less taxing to your amp. This is why you should always wire in series if you're connecting 2 speakers to a single amp.

    Hope this helps.
     
  6. ChrisWiggles

    ChrisWiggles Producer

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    Yes I realize that, but you see, if you wire in series, less resistance= more flow, so you will get the same volume wont you? Whereas if you wire in parallel, you have to boost the volume a lot to get the same output, so the end result is the same on the amp? There's no "magic" that goes on wiring in series that somehow makes it less electricity. Thats what I thought anyway. Anyone know for sure?
     
  7. TonyTone

    TonyTone Supporting Actor

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  8. Rich Chiavaroli

    Rich Chiavaroli Stunt Coordinator

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    In series, you're increasing the resistance. You're essentially putting 2 8ohm reisitors on a single line. This has nothing to do with power going back into the amp.. rather the power that's flowing out of the amp.

    When you're talking about parralel, 2 8ohm speakers would equate to 4ohm resistance. Resistance in a circuit is what limits the draw on the power supply. The less the resistance, the more the draw. The more the resistance, the less the draw. If you don't have enough resistance for your amp, you could over drive it, causing overheating and possibly burning it out.
     
  9. DanielN

    DanielN Stunt Coordinator

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  10. ChrisWiggles

    ChrisWiggles Producer

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    wow, yes, i dunno what i was thinkgin when i wrote that. flip the series and parallel around in my post.
     
  11. Kevin C Brown

    Kevin C Brown Producer

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    So if I do wire them in series, the R goes higher, would I find that when I did the calibration, would I have to increase the sound level to get them to match the rest of my system?
    Or, since there are two speakers anyway, would the sound level be about the same as just 1 speaker? Thanks!
    (I know, easy enough to try, I just haven't got there yet! [​IMG] )
     
  12. Earl Simpson

    Earl Simpson Supporting Actor

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  13. Kevin C Brown

    Kevin C Brown Producer

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    Another question for the rear speakers in a 7.1 setup.

    I have direct radiators for the front 3, bipolars for the surrounds. What should I do for the rears? Dipoles? Or direct radiators? I'm kind of limited in that the speakers will sit on a sort of shelf thing that's on top of my desk back there. So there won't be much space between them and the back of the shelf.
     
  14. Stephen Hopkins

    Stephen Hopkins HW Reviewer
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    Either bipoles or direct radiators are proffered for the rears. Since both speakers are playing the same material, 2 dipoles would make a rear sound stage that is overly diffuse and very muddy.

    Hope this helps.
     
  15. Kevin C Brown

    Kevin C Brown Producer

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    Stephen- I'm thinking more for either THX Ultra2 or Logic 7 type 7.1. Non-mono rears. Maybe it doesn't matter much?
     
  16. LanceJ

    LanceJ Producer

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    Question: Why do you need two back surrounds?
    A very, VERY large room maybe?
    I'm not trying to sound like a smart-aleck, but did a salesman tell you this? Seems unneccessary. And personally, I think two back surrounds--fed with the same signal--will smear the imaging back there. I wouldn't do it.
    BTW, doubling the speaker resistance will cut IN HALF the amplifier's output.
    Boston Acoustics makes a purpose-built speaker for the back surround channel:
    http://bostonacoustics.com/ProductsP...=1&SeriesID=35
    LJ
     
  17. DanielN

    DanielN Stunt Coordinator

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  18. Kevin C Brown

    Kevin C Brown Producer

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    2 vs 1 rear: I am trying to answer this question for myself right now. [​IMG] (Have 6.1, trying to figure if it's worth it to go to 7.1.)
    1) Logic 7 and THX Ultra2 put non-mono signals back there, so it doesn't have to just be mono.
    2) There is a acoustical effect called "reversal" where the brain can misconstrue sounds directly behind us to actually be in front of us. My impression is that 2 rear speakers can alleviate this somewhat.
    3) 1 rear speaker, depending on the room, can end up being quite close to the main seating position. Having 2 draws less attention to themselves than just 1 to itself.
    4) Ideally, the "surrounds" are beside you, L + R. With 2 vs 1 rears (single point vs "spread apart across the back"), theoretically you can get even better panning effects, for example.
    All this is from what I've read, other posts, THX Ultra2/Logic 7 literature...
     
  19. Kevin C Brown

    Kevin C Brown Producer

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    LJ- I checked out those BA's, and there is a slight falsehood in the description:

     
  20. Lewis Besze

    Lewis Besze Producer

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    Kevin,
    I had 2 DT BP1s as my back surround speakers,and dumped them for another 1 C1jr center speaker,this one is monopole,as my "side" surrounds are {Wharfedale SP-83],this new set up is more precise IMO,the bipoles were "smearing" the "imaging",in many case destroying some cool panning effects,like the flyover by Draco[Dragon heart].
    All my surround speakers are equidistant.
     

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