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Bi wire options

Discussion in 'audio' started by Darren L, Aug 4, 2019.

  1. PerF

    PerF Member

    I hate biwire terminals
     
  2. The Chronicals

    The Chronicals Disruptor

    Did they bully you?
     
  3. andrewd

    andrewd pfm Member

    I thought biwire went out of fashion 20 years ago? I much prefer to use a single run of high quality cables to speakers with high quality single wire terminals. I wouldn't buy speakers that need jumpers. It’s an unnecessary complication.
     
    Rockmeister and MikeMA like this.
  4. Michael J

    Michael J pfm Member

    I might get around to trying bi-wiring with my B&W DM600i speakers one day, but I'm not going to **** about with two sets of cables into one set of speakers unless I have actual active amplification with separate (possibly passive) crossover after the preamp output and in front of two stereo power amplifiers to feed genuinely and appropriately different signal ranges to the separate pairs of input terminals on each speaker. Bi-wiring is stupid otherwise, a waste of money and resources. Until then the thick, high purity, oxygen free solid copper slabs, with gold plating to inhibit surface tarnish on the bits that aren't screwed down tight between the bass and tweeter terminals, can stay where they are and the electrically separate internal crossover sections will remain joined together at the outside of the boxes for convenience. Only one set of cables required.
     
  5. MikeMA

    MikeMA pfm Member

    Yes, it must have been twenty or more years since I first tried it and found no difference. As you say it seemed to go out of fashion about that time but, as the saying goes, what goes around comes around, especially when manufacturers and their sales people think we've forgotten all about it.

    I've always thought there was a lot of wishful thinking and displacement activity in the world of hi-fi, much of it centred on wires.
     
  6. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    I hope that's a typo....

    Certainly if a single set of cables is short and thick then any advantages of bi-wiring are largely negated....
     
  7. Michael J

    Michael J pfm Member

    No typo. The actual electrical connections are effectively "airlocked" by the physical clamping of the slab under the terminals and will stay clean (as do grub screws in 2-pin DIN plugs), the gold plating is just to make things stay nice and shiny for those who want to look at the back of the speakers and not see brown copper surfaces on the slabs after several years exposure to air.
     
  8. joe9407

    joe9407 actress/activist

    i like this phrase.
     
  9. mercalia

    mercalia pfm Member

    Bi wring? One question, do you use the same cable for bass and tweeters? What is the effect of all that extra cable on the cross over - a few cm v metres between the bass and tweeter? can you duplicate any effect by using a cable twice as thick as the two single cables?
     
  10. Rockmeister

    Rockmeister pfm Member

    how can bi wiring work? Can one of the experts above who hear differences please explain it in (even basic) scientific terms?
    For a start the amp is not separating the signal into Low and Hi frequencies...those two binding posts on each channel at the back of your amp are just chucking out everything into the cable with no discrimination. Both L channel posts are getting all L channel frequencies and ditto on the right...so down each of the two cables goes the same signal to each speaker binding post, and I guess 100% of it arrives at the speaker untouched. Now what we need to do is to look inside the speaker to see how the crossover is constructed. Because if it all gets combined into one cable just inside before the crossover circuit (or if the two are separate but both are soldered to the crossover entry point together) nothing can be or should be heard. So if you hear something you need to ask...why?
    The only possible difference might be if one set of cables was designed to act as a filter of some sort (ie the treble output uses cables with bit added for example) then one might expect to hear something unless, inside the speaker, both signals merge before entering the crossover.
    Come back at me once you've looked inside and worked out the circuit and what the electronics are doing.
    If the two arrive at different parts of the crossover, then still, just remember those two cables are carrying identical signals. No difference is possible is it?
    OR, consider that, if you spend all that BiWire money on a single cable, won't you have something you believe to be twice as good?????
    Man that'd be something! :)
     
  11. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Just in case it's not widely understood....

    The idea behind bi-wiring is to prevent interaction between bass and treble (assuming a 2 way speaker) signals to the respective drive units due to the resistance of a single run of cable shared by both. By Ohms Law V=IxR. I is current, V Voltage and R resistance. Hence when a current is delivered to the speaker a voltage is developed between the amp and speaker ends of the cable due to its resistance. Now if a kick drum gives a big current to drive the bass unit then a voltage in sympathy with the waveform of the kick drum will be developed across the speaker cable and this will modulate the envelope of other frequencies such as a cymbal feeding the tweeter... and vice versa.
    The back EMF of the drive units sending a current back to the amplifier will experience the same effect due to the same cable resistance.
    This effect is added to by the same process in the internal speaker cable and shared tracks on the crossover PCB.

    In a bi-wire speaker the crossover is electrically separated into the bass and treble sections with no connection between them. + & - on each drive unit goes to + & - on its own part of the crossover which then goes to its own + & - terminals on the rear of the speaker and thence via its own cable back to the amp and so they only connect together where they meet at the back of the amp. QED there can be no interaction between the bass and treble sections due to the resistance of a shared single run of speaker cable. Bold there for a reason;)

    It should be apparent from this that 4 Ohm speakers will suffer worse than an 8 Ohm one from a single cable run and that speakers with a nasty dip to say 2 Ohm's in the bass will make it much worse around this dip.

    So that's the theory...

    In practice amplifiers are not perfect voltage sources, which is another way of saying they have internal resistance and can't provide infinite current to a perfect short circuit... another way of expressing this is that they don't have infinitely high damping factor. Now (to keep things simple) it can be said that this internal resistance of the amplifier is exactly the same as a the resistance of a single run of cable electrically speaking. So although we may have provided separate cable runs to the speaker by bi-wiring it is, electrically, as if they then share a single unseen run of cable inside the amplifier, which just moves the problem back to the amplifier end and partially negates the effectiveness of the bi-wiring.

    It should be clear from the above that the higher the damping factor of the amplifier the more potential advantage to the bi-wiring.

    It should also be clear that the thicker and shorter you make a single run of cable then the less its resistance and so the less the "interference" between bass and treble at the speaker end...

    ....and that an amplifier with a low damping factor is going to cause so much of this "interference/interaction" due to the "long imaginary single length of shared cable inside it" that there will be little or no advantage to bi-wiring OR, and for the same reason, to using a single cable run of mega thick cable.

    It can be seen from all this that the greatest potential improvement from bi-wiring will be when using an amplifier of high damping factor.... which means a high feedback solid state amplifier... and that little if any advantage will be apparent with low feedback low damping factor amplifiers such as most valve amplifiers... and indeed some of the best sounding low feedback SS amps.
    FWIW I'll point out that Naim amps have an actual physical 0.22 Ohm resistor at the output anyway which is equivalent to a shared run of lets say 10 meters or more of 79 strand speaker cable inside the amplifier between the PCB and the speaker terminals... so not a good candidate for potential improvement from bi-wiring!
     
    chris@panteg and Rockmeister like this.
  12. chartz

    chartz pfm Member

    Snake oil, period.

    Trouble is, manufacturers have to supply biwireable binding posts to sell their speakers. I'm sure they know - because they muster the basics of loudspeaker design - it's just that, snake oil. But when you have a business to run, you might just compromise a bit!

    Anyway, nor my ESLs nor my Cabasse Galion are biwireable.
     
  13. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    No it's not.... it does have sound theory behind it as I just explained at great length!

    I'd agree though that for most people in most situations it is just a way of selling more cable and banana plugs etc.

    If you have a high damping factor amp it could have some advantage but such amps tend to be amongst the least good sounding anyway...
     
  14. Julf

    Julf Evil brother of Mark V Shaney

    Are you saying amps with a high output impedance sound better?
     
  15. mjw

    mjw pfm Member

    Just assume he is and go for it.
     
    Wilson likes this.
  16. Julf

    Julf Evil brother of Mark V Shaney

    I would love to see a SPICE simulation or actual measurements showing that effect.
     
  17. Julf

    Julf Evil brother of Mark V Shaney

    Just curious as to what he would base such a statement on.
     
  18. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    I'm saying amps with low feedback sound better... generally
     
  19. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Again, I would have thought it obvious...
     
  20. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Only partially relevant but "Interface Intermodulation in amplifiers" R. Cordell, Wireless World Feb 1983 may be of interest;)
     

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