Question about biwiring vs single wiring

Discussion in 'Home Theater Projects' started by Kevin C Brown, Sep 13, 2003.

  1. Kevin C Brown

    Kevin C Brown Producer

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    If I can bi-wire the front 3, but the surrounds and rears can't be, and if I want to "balance" the gauge all around, how would I do it?

    For example:

    a) front 3 biwired with 16 gauge for each conductor (16 + 16 = 13 gauge), surrounds & rears with 14 gauge

    b) 14 gauge all around

    Am I thinking correctly that (a) is what I want because since I'm splitting the load between the low and high freqs, that the gauge does effectively add together?
     
  2. brucek

    brucek Second Unit

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    Kevin,

    Since your speaker cables are likely to be different lengths, I feel your plan of 'balanced' gauges has a few holes in it. Not that it would matter, but you would have to make the calculation of length combined with appropriate gauge to ensure the resistive load was matched all round. The result of course, is that your inductive reactance wouldn't match all round since the longer cables would have a higher cumulative inductance (since gauge has minimal effect on inductance per foot). This would throw off any chance of balanced impedance.

    My guess is that all you're looking for is the best sound for a reasonable price, and since the science behind bi-wiring is questionable at best (anecdotal evidence only), my advise would be to spend money on something that's actually got a chance of making a difference and use a single good quality 10 gauge cable all round, and keep them short as possible - it's not expensive in bulk. That's it...... [​IMG]

    brucek
     
  3. Kevin C Brown

    Kevin C Brown Producer

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    Cool. I guess I was only really looking to biwire the fronts just because it could be done, not necessarily because I believed I'd get any sonic benefits. [​IMG]
     
  4. SeanA

    SeanA Second Unit

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  5. Kevin C Brown

    Kevin C Brown Producer

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    Sean- No, not balanced as in the physical sound level meaning, but "balanced" as in the same effective gauge.

    If the signal is being split between high and low freq for one run, then would a higher gauge for each run of the bi-wire be effectively the same as using a lower gauge but single wired?
     
  6. brucek

    brucek Second Unit

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  7. Bill Kane

    Bill Kane Screenwriter

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    Bruce, it's nice to see you posting again at HTF...

    I decided to replace the "gold" terminal straps on my Paradigm spkrs 6 mos ago -- on the basis of your observations then.

    After a year's experience bi-wired, I heard no change, anecdotally speaking. I'm keeping the Monster basic HDXP cable in place for an effective 11-12 gauge connection.[​IMG]

    bill
     
  8. Matt_Doug

    Matt_Doug Stunt Coordinator

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    I was reading the "market speak" on Audioquest's website and they claim a benfit of biwiring is that there is better filtering of bass and mid harmonics from the high frequency path resulting in cleaner highs and a more defined mid and bass To my ears I've always heard subtle improvements with biwiring mainly better definition.
    As per balanced impedance all round, to what pupose?
     
  9. Chu Gai

    Chu Gai Lead Actor

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  10. Chu Gai

    Chu Gai Lead Actor

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    How does the wire know what frequency it's supposed to handle?
     
  11. Matt_Doug

    Matt_Doug Stunt Coordinator

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    the crossover and Ohm's law E=IxR or rather E/R = I From which you can see at any given E voltage when R (Impedance) is infinitely high, I (current) will be 0. frequencies rolled off by the crossover have infinite impedance and current will not flow to the speaker at those frequencies. Which means that in a biwired system certain frequencies can be relegated to a particular wire depending on the crossover points [Edited for incompetence [​IMG]]
     
  12. brucek

    brucek Second Unit

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    Interesting article Chu. I can't argue with his math - don't know much about speaker design.

    Most solid state amplifiers possess an output impedance that is fairly constant (read linear) and very, very low over the entire audio spectrum and as such can almost be ignored in the damping formula because the 'system' impedance is overwhelmed by the non-linearity of the speakers crossover plus the interconnecting wire resistance.

    This is the reason to ignore small differences in amplifier specs of damping. It's usually insignificant in relation to the effect of the speaker wire. Damping factor is increased with heavier wire.

    The article states low damping factor is not audible.....OK ....but as he claims himself, the article only looks at motion control at resonance for a speaker and does not consider frequency-dependent attenuative effects of the source resistance. This includes high impedance values of speaker cable....

    When the wire resistance becomes an appreciable portion of the system impedance you'll get distortion. Place a 2 ohm power resister in series with one of your speakers and listen.....ever heard an old tube amp...mush


     
  13. Chu Gai

    Chu Gai Lead Actor

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    I think even Pierce concurs with your comments regarding situations where either the wire becomes a significant contributor to the speaker impedance (but then that's a silly way to spec and run wire, don't you think?) or the output impedance of the source becomes substantial. Pierce's point I think was directed in part to the pissing matches some amp makers have with their 'damping factor' being greater than the average competitor with his general point being that of Shakespeares...much ado about nothing.
    BTW, any way of contacting you via pm or email?
     
  14. Kevin. W

    Kevin. W Screenwriter

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  15. brucek

    brucek Second Unit

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  16. SeanA

    SeanA Second Unit

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  17. Chu Gai

    Chu Gai Lead Actor

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  18. brucek

    brucek Second Unit

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    Sean,

    There are some points that you're confused about. Instead of trying to dissect everything you said, I'll just give you a general overview. It may help.
    A power amplifier has a low output impedance. It's not a perfect voltage source, but in relation to it's load (which is significantly higher), it can be considered as such for rough calculations. We can consider all the voltage at the amplifiers output will be dropped across the load and none will be lost to the amplifiers output impedance.

    In your argument you are ignoring the important difference between simple DC resistance (DCR) and impedance (frequency dependant resistance - the resistance to an AC signal). The wire and specifically the crossovers are all affected by frequency, making the calculations a little more difficult.

    In a bi-wire situation if I consider a particular frequency (say 20Khz), the amplifier see two loads that present a different resistance to current flow. The LF path presents a high impedance to the signal and little current flows. The HF path presents a low impedance path and lots of current flows. Considering the amplifier is a good voltage source and is capable of supplying all the current required for the two loads , no voltage will be lost and the same voltage will be applied to both loads with the current determined in each leg by the additive impedance state of the crossover, speaker cable and driver coil.

    The important point to note is that these separated current flows can exist on the same wire just as easily as they can on two separate wires. Simple fact. As I said before, the Superposition Theorem states this, and it is so. There is no disputing it.

    Generally the separated LF and HF current flow resulting in a 'better sound' because the two signals somehow 'affect' one another on a single wire isn't the disputed issue with the camp that supports bi-wiring. Most know it's indisputable - the science just ain't there.

    The main contention is that bi-wiring helps because there's a possibility that one of the drivers (i.e LF driver) in a speaker may distort, producing harmonic products, so the current flowing to that driver may possess a small distortion component. That component, flowing through the speaker cable, causes a distortion voltage that appears in series with the output of the amplifier.

    Now, if I don't bi-wire, and if I assume that the cable has a finite impedance, those harmonic components in the current will cause a small harmonic voltage between the amplifier's output and the speaker's input. So the tweeter will also see this small distortion voltage. But when I biwire, the other driver will not see that distortion voltage, that it will be damped through the low impedance path to ground provided by the amplifier and not travel back down the 'other' cable in the bi-wire to its driver, while on the contrary, if I use only one pair of cables, then that distortion voltage is presented to the other driver through the strap.

    Well, the idea has merit, but there are a couple of problems with this theory.
    The rubric of this statement hangs on the calculated difference in the impedance between the speaker's straps and the impedance of one pair of the bi-wire cable. The assumption is that the speaker cable presents a non-zero impedance (which it does), and that the distortion can indeed reach and affect the other driver. Ahh, there's the rub - Not likely. Consider the fact that a speakers common terminal "straps" are extremely close in impedance to the near zero impedance path through the bi-wires to the other driver. This is the difference you're considering. Yes, the currents to each driver are different in bi-wiring, but the voltage is the same because the amplifier is a near perfect voltage source. The distorted harmonics generated by each driver will be short-circuited by the low impedance output of the amplifier in either case.

    Also consider that harmonics are second and third order effects, and consider that the harmonic would have to get through the other driver's crossover, which would be in a high impedance state to that harmonic frequency. Again remember that these calculations are to be performed on the 'difference' between the impedance of the speaker's straps and the impedance of one pair of the bi-wire cable. You better have your calculator set to many, many decimal places......

    As I said before, as far as bi-wiring is concerned (if you already are using it), you'd probably be better off using bi-wire cables with your speaker straps reinstalled. At least then you'd take advantage of the lower gauge realized by combining two cables to each speaker. It would certainly help the LF drivers damping path to ground through the amplifier output. At least here we can make the calculations to prove that heavier wire is beneficial.

    If you like bi-wire, then use it, no harm done......It's ineffective, others will disagree. It's about as effective as trying to slow down your car by putting your hand out the window. I suspect you could make the calculations on the effect, but why bother.................. [​IMG]

    brucek
     
  19. Matt_Doug

    Matt_Doug Stunt Coordinator

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    The harmonics of mid band frequencies close to the HF crossover roll off should fall above the frequency roll off the HF crossover. So ask yourself how exactly does a crossover know the difference between distortion and fundamentals at the same frequencies. I suggest to you it doesn't. Your best argument against is that the voltage of the distortions is so small that the resultant current flow isn't strong enough to get pass the HF crossover circuits let alone drive the speaker. And relative to the voltage of the fundamentals you probably won't hear the distortion anyway. Love your "slow down your car by putting your hand out the window" analogy. But as you know audiophiles (among whom I'm not worthy to count myself) with their ultra high end gear would balk at your suggestion that the distortion would not audible in thier systems. And there are so many variables involved between varied systems and environments how could you disagree with absolute assurance. Better to take the apporach to get rid of the cause altogehter than argue about the level of the effects.
    I don't pretend to understand how the impedance of the shorting straps figure into all of this but it seems logical that no shorting straps with absolute 0 impedance is better than a shorting strap with relatively low impedance. [Edit: scratch that. The straps present a path for distortion from the low to hi crossover sections that could be audible in the HF driver. no shorting straps no path for distortion] And I still don't get the benefits of balanced speaker wire impedance all-round.
     
  20. brucek

    brucek Second Unit

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