bi-amping mistake in technical terms

Discussion in 'Amps, Pre-Pros & Receivers' started by M. Galyean, Feb 17, 2017.

  1. M. Galyean Audiophyte

    M. Galyean
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    Hi,
    need to explain the technical side of a mistake a tech made, just unsure of exactly what is happening in electrical and signal terms. Basically used a passive bi-amping layout, connecting both HF and LF on the speaker from the same amplifier output.... but did not pull the bridge clips... Need to explain to him and the client exactly what is going on.
    Thanks
  2. rojo Audioholic Samurai

    rojo
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    Technically it's just a waste of wire.

    Bi-amping is only applicable when you're applying different filters to the different drivers and the amplified signal is different. If you have no passive crossover, if you're sending a high-passed pre-amp signal to one amp channel and a low-passed pre-amp signal to a second amp channel, then drive the tweeter with channel one and the mid with channel two, that's bi-amping. If the speaker has a passive crossover built-in, bi-amping requires bypassing that built-in crossover in favor of an active one at the pre-amp stage.

    What you're doing is bi-wiring. There's no audible benefit to bi-wiring. Doesn't matter whether the bridge is done at the amp, at the speakers, or both as you describe. It's the same signal going to all drivers regardless.

    I'll offer one concession, though. If the speaker wire is cheap copper-clad aluminum or is insufficient gauge, then doubling up on the wire can help avoid insertion loss. But if you've otherwise got sufficiently thick wire to handle the signal at a given distance with speakers of a given impedance, then doubling up on the wire does nothing useful.

    Useful reading:

    http://www.audioholics.com/frequent-questions/the-difference-between-biamping-vs-biwiring
    http://www.audioholics.com/audio-video-cables/speaker-cable-gauge
    rojo,
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  3. M. Galyean Audiophyte

    M. Galyean
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    Thanks, while I am familiar with the uses and pros/cons of bi-amping and bi wiring, I'm looking for the technical side of the biwiring mistake of biwiring and not pulling the bridge clips from the speakers.
    Thanks
  4. j_garcia Audioholic Jedi

    j_garcia
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    With Biwiring, the two wires are connected to one terminal on the amplification side, so whether the jumper is connected or not, it yields exactly the same thing. No risk of damage but also no benefit either.

    If truly biamped then not pulling the jumpers will feed back current to each amp channel, potentially frying both channels/amplifiers.
  5. PENG Audioholic Warlord

    PENG
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    If you don't remove the jumpers at the speaker terminals, you are not even bi-wiring. If you remove the jumpers then you are truly bi-wiring but most people believe it won't make any difference in sound quality if cable size is not an issue to begin with.

    Edit: I suddenly realize you are asking about the "technical" difference due to that mistake.
    Technically speaking, if you don't remove the jumpers at the speaker terminals, then the crossover in the speaker is still in one piece so it will present the same impedance to both pairs of wires between the amp terminals and the speaker terminals. That means the current flow in both pairs of wires will be the same. Current = Voltage/Impedance and impedance is a complex function of resistance in ohms, inductive and capacitive reactance (also in ohms but both vary with frequency).

    With the jumpers removed, the crossover in the speakers will be split into two. The amp terminals, though the same single voltage source in bi-wiring, will see two different impedance load at the other (speaker) ends, one being basically a high pass filter and the other low pass filter, so the currents in the two pairs of wires will be different, with one pair carrying mostly high frequency signals and the other pair low frequency signals. Again, most experts believe any such technical difference will not result in audible difference.
    Last edited: Feb 17, 2017
    PENG,
  6. lovinthehd Audioholic Ninja

    lovinthehd
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    I'd offer him a refund on the stupid extra wiring rather than try and rationalize it.
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  7. highfigh Audioholic Warlord

    highfigh
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    The cables meet at both ends- it doesn't matter and it won't cause a problem. If two different channels had been used, it could cause problems.

    Turn the amp off, check the resistance from each cable + to the other, then repeat it and measure between the - cables. You should see zero Ohms, or very close to it. Then repeat the measurements at the speaker end- you should see zero Ohms, or very close to it.

    Seems that this was done by someone who really doesn't understand bi-wiring OR bi-amping.
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  8. rojo Audioholic Samurai

    rojo
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    I have a related test to perform. Turn power off at the amp but leave the speaker connected. Leave the terminal bridges attached to the speaker terminals.

    Using a multimeter, measure resistance with one probe on one + speaker binding post, and the other probe on the other + speaker binding post. Now disconnect the bridge and repeat the same test. The difference should be negligible, if any.

    Bi-wiring while leaving the bridge attached may offend OP's OCD, but it's no less effective than without since neither configuration offers any benefit over a single wire pair with the binding post bridges engaged.

    And luckily one does not need golden ears or expensive equipment to test this. It can easily be proven with a simple multimeter.

    I suppose it's even possible that the original installer ran two pairs to each speaker with redundancy in mind. This way if a cable gets damaged, there's still a working pair in place. Could also be future proofing in case the client wishes to implement true bi-amping, and new cables won't need to be pulled. Same reasons Cat5 cable is 8-conductor, but only four are needed for Ethernet.
    Last edited: Feb 17, 2017
    rojo,
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  9. PENG Audioholic Warlord

    PENG
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    Multi-meter only proves the resistance of the two pair of wires are the same. You still need golden ears to prove the fact that each pair carries different signals but converge at the other separated ends makes no audible difference.:D
    PENG,
  10. Pogre Senior Audioholic

    Pogre
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    Here you said you were using a passive bi-amping layout.
    Do you mean the same channel? If so, that is bi-wiring and not bi-amping. Passive bi-amping requires 2 separate amplifiers, or at least 2 separate channels (pretty much equally useless as bi-wiring).
    If it is bi-wired there will be absolutely no difference if you leave the clips on or off. If it is passively bi-amped, you're gonna have problems beyond my scope to describe outside of using words like "fry" and "destroy". Others here can explain it better. Your post is a little confusing though.

    The best way to wire those is to just leave the jumpers on and get rid of the extra wire altogether, as has been stated. Good luck.

    *Edit: Here's another good read - http://www.bigfootmusic.com/blog/archives/2014/06/13/bi-amping_for_dummiesand_smarties
    Last edited: Feb 17, 2017
  11. highfigh Audioholic Warlord

    highfigh
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    I don't know who started it, but I have seen photos of cables connected to the woofer positive and the tweeter negative, as if that will make a difference. I guess it might, on some infinitesimally small scale, but it sure as hell isn't audible.

    Cat5e uses two pair, but Cat6 and Cat7 use all four and those have consistent twist rate, l Cat5/e, which has four different rates for the pairs.

    I have been stocking less 16/2 and more 16/4 cable because it's generally not a problem to install and if the speakers are high quality/amplifier power is higher, doubling it doesn't hurt. If I'm installing in-wall or in-ceiling speakers, I run it to the speaker location that's closest to the volume control or amplifier, leave a loop and continue to the next speaker. When it's time to connect the speakers, I slit the jacket and remove enough of the needed pair and connect it to the speaker. I don't need to carry multiple boxes of cable just to pull four conductors and it makes things move faster during the installation. I have never bi-wired a single speaker in almost 40 years in the business and I don't plan to start now. Maybe I'll try it after I retire and if I find that it makes a positive difference, I'll live out my life, filled with regret. :D
  12. Pogre Senior Audioholic

    Pogre
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    I think the op bailed. Sounded like he had a client he needed to soothe asap. His post was confusing, no? Said he was passive bI amping, but described a bi wire setup?

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