Combining A and B Powered Outs

Discussion in 'AV Receivers' started by Keith Hyde, Feb 9, 2004.

  1. Keith Hyde

    Keith Hyde Stunt Coordinator

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    This has to do with speakers as much as amps, but I'll only post to Amps:

    This may sound stupid, but...

    When you bi-wire speakers, you remove the bridges on your multi-pair speaker terminals (tweets and subs) so you have an amp of X watts feeding the speaker X watts to the upper pair, and X watts to the lower pair. 4 receiver outs (A set pair and B set pair), 2 -/+ wires, 4 speaker terminals used (two pair).

    What happens if you forget and leave the +to+ -to- bridges on your speaker terminals when bi-wiring?

    What happens if you bridge +to+ -to- A and B sets at your receiver and send a single lead to a single pair or terminals at the speaker (say, if you only have a single pair at the speaker)?

    I am guessing that we are then talking about receiver damage, smoke, and fire, but I'm not certain.

    Thanks.
     
  2. Mike_Skeway

    Mike_Skeway Second Unit

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    You will short out the amp in both cases. Depending on the amp it may or may not cause damage.
     
  3. Keith Hyde

    Keith Hyde Stunt Coordinator

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    One of those hairbrain ideas that didn't smell right. Still learning. Good to know for certain beforehand. Thanks.
     
  4. Mike_Skeway

    Mike_Skeway Second Unit

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    No problem, always good to ask before you melt something. [​IMG]
     
  5. Wayne A. Pflughaupt

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    How? It’s not the same as if there were two amps involved and two independent output stages. The “A” and “B” terminals on a particular amp are internally paralleled to the same output stage.

    Now, if you send the left and right to the same speaker with the jumper in place, then you'd have a problem.

    Regards,
    Wayne A. Pflughaupt
     
  6. Mike_Skeway

    Mike_Skeway Second Unit

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    Sorry, I may have miss read something. Putting A+B together using the same + and – and left/right from each will do pretty much nothing.
     
  7. Keith Hyde

    Keith Hyde Stunt Coordinator

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    Will it do nothing or supply a speaker with more juice (the idea being reducing clipping and making use of an unused B set)?
     
  8. Mike_Skeway

    Mike_Skeway Second Unit

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    Nothing, you are using the exact same amp channel.
     
  9. Wayne A. Pflughaupt

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    By "nothing" we mean it won't damange the amp. That was the original question.
     
  10. Mike_Skeway

    Mike_Skeway Second Unit

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    And it won’t improve or add power. [​IMG]
     
  11. Ray_C

    Ray_C Stunt Coordinator

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    You won't get any more juice or current into the speaker. The A/B terminals are connected to the same power section, to be used in case you have a pair of speakers set up in another room and want to use just one receiver for both entertainment center listening as well as in another room. Bi-wiring using both A/B terminals will be no different than bi-wiring using just the A or B terminals alone. If the A/B terminals each had separate amp sections (like your other channels), then we'd be talking about bi-amping, which is a different matter.
     
  12. Keith Hyde

    Keith Hyde Stunt Coordinator

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    Thanks. Since I didn't know any better I thought it was worth a shot.

    But I am curious, how do people bi-wire their speakers then? Do you have to have an amp with four outputs per channel? I thought the idea behind it was running full wattage to one pair of speaker posts, your high range, then two, your low range speaker posts (four total binding posts on the speaker). What are the amp connections?
     
  13. Wayne A. Pflughaupt

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    You are correct, that is biwiring. Both wires connect to the same amp. The other arrangement you mentioned, using two separate amplifiers, is biamping.

    Regards,
    Wayne A. Pflughaupt
     
  14. Keith Hyde

    Keith Hyde Stunt Coordinator

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    I thought this thread was done, but looking at my Paradigm manual last night got me curious on another very related thing.

    Why in the heck would you bi-wire a speaker that comes with (removeable) speaker terminal bridges? On a bi-wireable speaker, the manual showed a single pair of AVR outputs, each one with two wires (that's four wires altogether), the result being each of the four speaker binding posts got their own wire in lieu of the using the bridges. Well that's all nice, but what's the benefit when the speaker comes with nice shiny ++ -- bridges (such as the Paradigm Studio line)? Seems to me there is none, unless you are using Rat Shack 20+ guage wire to drive your nice speakers. Odd.
     
  15. John Garcia

    John Garcia Executive Producer

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    Those "nice" jumpers are flat, gold plated BRASS. Just replacing them with some decent wire alone is worth it.

    BIWIRING is not as effective as BIAMPING, as Wayne points out, which is the true purpose of the separate terminals. Running both terminals off a single amp is an improvement over the included jumper, but is not going to give you a night and day difference.
     
  16. John S

    John S Producer

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    Bi-wire'ns big advantage is that the Bass signals, and mid/tweet signals, do not travel on the same wire to the speaker. They travel on different wires to the speaker.

    Now bi-amping, which requires external electronic cross overs, sends the bass signals only to one amp, and the tweet/mids to another amp.
     
  17. Keith Hyde

    Keith Hyde Stunt Coordinator

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    Okay - I see. The fundamental concept missing in my puzzle. Perhaps I WILL go for the extra length of cable next time I go shopping.

    Thanks.
     
  18. John Garcia

    John Garcia Executive Producer

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    Biwiring from a single amp terminal gives you full range on each wire, the x-over doesn't take over until it gets to the speaker. The single amp channel "sees" exactly the same thing when running two wires or one. You are effectively increasing the wire ga. to each terminal.

    You don't need external x-overs to biamp. Passive biamping does not frequency limit prior to the amp stage. Active biamping, using external x-overs, does do this - but you still have passive x-overs built into the speaker to contend with.
     
  19. Wayne A. Pflughaupt

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    That’s not generally how it’s done in home audio, John. When you remove the jumpers you have direct and separate access to the passive crossover’s high pass and low pass sections. Most people who bi-amp drive them with separate amps.

    I know - coming from pro-audio you find this pretty cheesy, and frankly so do I. But that’s the way it’s usually done. The people who are in this hobby at this level typically don’t want to add another component to the signal chain - i.e., the crossover – although personally I’d much prefer that to a bunch of capacitors, coils and chokes. Not to mention, as Mr. Garcia noted, it would require modifying the speaker to bypass the passive crossover – not the kind of thing most people want to do with their expensive speakers.

    Regards,
    Wayne A. Pflughaupt
     
  20. Mike_Skeway

    Mike_Skeway Second Unit

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    Yeah, I would not add another crossover to the path, and I would not modify my HT speakers to active bi-amp. I do tri-amp all my PA gear however.
     

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