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Ok I give up, Bi-Wire and Bi-Amp?

Discussion in 'Home Cinema Speakers' started by slyborg, Aug 19, 2003.

  1. slyborg

    slyborg
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    Hi,

    Hunted around for some info but to no avail. If someone can point me in the direction of some good sources for info I'd appreciate it. I'm trying to find out what the 2 Bi- terms mean exactly. Then I can decide whether I need to worry about them as I'm about to buy cable and am also getting a Pio VSX2011 that I'm led to believe I can bi-amp my front speakers with (lord only know how)

    Cheers

    Si
     
  2. Ian J

    Ian J
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    Some speakers have two sets of terminals on them with one connected to the tweeter and the other to the bass / mid range speaker. Rumour has it that the speakers can sound better if each driver within the speaker is connected to the amplifier via a different cable and this is called biwiring. Many think that this is an invention of cable manufacturers to sell more cable.

    Bi amping is when the same two speaker connections are connected to two seperate amplifiers
     
  3. slyborg

    slyborg
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    Thanks so I'd be correct in saying that:

    1. You can't bi-wire if you only have one set of terminals (on speaker)
    2. You can't bi-amp if you only have one set of terminals (on speaker)
    3. You have to bi-wire if you want to bi-amp

    Si
    PS: I can well imagine the sceptisism surrounding the bi-wire thing, I have to wonder if there is any scientific proof. A guy at a shop did say that you WILL notice a difference with bi-amping and you MAY notice a difference with bi-wiring
     
  4. Ian J

    Ian J
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    All three statements are true
     
  5. Big Adam

    Big Adam
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    With regard to the Pioneer 2011, this receiver has seven separately amplified channels (Front Left, Front Right, Centre, Surrond Left, Surround Right, Rear Surround Left, Rear Surround Right) plus a separate channel for your subwoofer.

    If you have a 5.1 speaker setup, you can use the two rear surround channels as your "extra amps" to connect to the second set of terminals on your front speakers (as Ian J described). In this way you will be bi-amping the fronts.

    If you have a 7.1 speaker setup, you do not have any spare amplified channels so may only bi-wire the fronts.

    As an alternative to these arrangements, the 2011 allows you to use the Rear Surround Terminals as a pair of separate stereo terminals, allowing you to run wires to a pair of stereo speakers in another room (or even outside for parties!). You may run these speakers with your main 5 speakers switched off.

    Big A
     
  6. Dangermouse2000

    Dangermouse2000
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    In response to whether or not Bi-wiring is beneficial....

    I have my B&W 602's bi-wired and there is a good increase in sound quality. I can easily hear an increase in clarity and dynamics.

    Bi-wiring will give different results depending on what speakers you have. B&W's excell when bi-wired, yet other makes and models won't change.
     
  7. slyborg

    slyborg
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    I've also seen similar comments about the benefits of bi-wiring but they often say it's only worth it on the front 3 speakers? It also saves you a shed load of cash :) I'll be using VM1s all round if this makes any difference (need to check now to see if they can even be bi-wired)

    Si
     
  8. Dangermouse2000

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    I only have the front three bi-wired. It would cost too much to do the rears. May think again if/when I get into Multichannel music.

    I've just download the VM1 manual from the B&W site. According to the diagrams, it looks like they have only a singe set of binding posts. :(
     
  9. slyborg

    slyborg
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    Hmm now I'm debating all round VM1s vs 602s front, 601s rear and LCR60 centre *sigh*

    Si
     
  10. MuFu

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    I wouldn't rule out the VM1s on the basis they can't be biwired.

    I biwired my 601s3s and found it made a timbral difference but honestly couldn't say whether it was for the better or not after a few weeks listening.

    MuFu.
     
  11. Dangermouse2000

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    Thats the setup I have. All series 2's though, not the new series 3's

    602's are great for front effects and music. Although you will need a sub for the LFE. I'm not too keen on the LCR60. It isn't as clear as the 601's and 602's. And dialog can sound dull at times.

    This should be improved in the series 3 LCR60 as it now has the nautilus taped tube tweeter, unlike the series 2 counterpart.

    Along with good stands for the 602's and this system will knock your socks off!

    :D
     
  12. SeaneyC

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    I bi-wired my Mission M74s, but can't say it made any discernable difference to the sound. Bi-amping on the other hand makes a noticable difference, but only you can decide whether it's worth the price hike or not.
     
  13. slyborg

    slyborg
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    I'd be looking at the S3 models in particular. I'm going to see if my local dealer can demo the 2 systems together.

    Oh and I'll be putting these in a shelving unit rather than floor standing, not sure how much of a difference that will make.

    As for base I have an SVS PC+ 20-39 on order

    Si
     
  14. Adam M

    Adam M
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    I only ever heard one satisfactory explanantion as to the benefits of biwiring and it came from a linn dealer in leeds.

    It was simply that the cabling could be chosen differently for different speakers (hi and low frequency) as the attenuation charcateristics of cables vary enormously.

    When you plug in a cable to a terminal it is a transmission line and you will get reflections at every terminal along the signal path. The attenuation of these reflections can be specific to the frequency of the relfections and so cabling with the tweeter or mid range in mind can improve the sound.


    Prior to hearing this exlpanation, I had people trynig to fob me off saying that they could hear the difference when they inserted the cable in the top or bottom terminals on the back of the speaker, ie. they could hear the effects of the bus bar paralleling the terminals.

    when I asked them to show me the difference in the circuit diagram between biwiring and single wiring, none of them could. Thats because there wasn't one. I now use this as a test to determine how much believe anything they ever tell me!
     
  15. Nic Rhodes

    Nic Rhodes
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    It is a pity it is a complete load of garbage! :( We are talking audio frequecy signals here not digital / video signals. If we consider the highest freq that SACD / DVD A are likely to produce will be of the order of 50 Khz, then what is the wavelength?

    I will tell you 6,000m, now how does your 3m of speaker cable supposed to effect that if transmission line has an effect or do Linn dealers use VERY long speaker cables?.

    You have unfortunately been told a complete load of rubbish, now what do they do, ah yes they sell cable! :)
     
  16. NicolasB

    NicolasB
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    I don't buy that explanation, I'm afraid. Even if the effect you're talking about were detectable at audio frequencies (and I don't think it would be) it's very unusual to hear anyone talking about the benefits of using two different wires when bi-wiring, they are virtually always talking about using the same type of cable for both terminals (and claiming to hear a big difference).

    The only plausible suggestions I've ever heard are:

    a) that the shunt used when single-wiring tends to be crap, or
    b) that bi-wiring halves the resistance of the cable, or
    c) that it's all just placebo effect anyway.

    I suspect the cable resistance issue may sometimes be significant. It's interesting that people often cite B&W speakers as an example of biwiring causing a detectable improvement - B&W speakers are also infamous for occasional ultra-low-impedance swings.

    I suppose it's also possible that having more wires strewn about influences the cable's capacitance in some way....

    Edit: corrected incorrect spelling of "resistance", in an effort to appear less of a fool.
     
  17. Adam M

    Adam M
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    a valid point, but what about the LC effect of a length of cable?

    transmission line or not.

    a length of coil has an inductance. does this not have the ability to attenuate different frequencies.

    I am clutching at straws here to defend something that made complete sense but may have been diluted by the gaps/ vasy casms in my knowledge.
     
  18. Calle

    Calle
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    I've heard an explanation that was about lower frequencies needing more power than high frequencies, which means that the benefit of biwiring would be that the bass and treble takes separate paths from the amp (really speaker posts). This would mean that high frequencies don't get distorted by low frequencies (much the same reasoning as the .1 channel in DD 5.1?)

    I'm somewhat sceptical, but not knowledgeble enough to prove this wrong.. anyone? ;)

    I can believe this when biamping, but biwiring.....
     
  19. Nic Rhodes

    Nic Rhodes
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    I wrote this a long while ago now

    http://www.avforums.com/forums/showthread.php?threadid=46335&referrerid=15820

    Pure R will just reduce the voltage leading to lower volume levels, it will not effect the sound quality. R is additive

    C is additive as well. This will only effect the treble roll off of the cable. This again will only become an issue if this falls into the audible band. Properly designed cable / amp this should not be a problem even for very long lengths. It might be an issue with a poorly designed amp with no 'driver' stage but not good kit. I am not advocating 100m but just used it as an extreme example. What people really want to do, if the kit is properly designed in the first place (not as common as it should be unfortunately) is to use long interconnects and site amps next to speakers with short LS leads (shielding issues etc). Unfortunately most people do it the other way around and therefore suffer the 'degredation' in performance.

    More general stuff info:

    If the output impedance of a good preamplifier is low, the input impedance of a good amplifier is high, and hence the current is minimal. With the current being minimal, and the frequency be limited to the audio band, we simply need a well screened analogue interconnect. It is simple physics. Que the ‘tweako’ cable brigade.

    The situation is different with a power amplifier to loudspeaker connection. Here we have a small output impedance of the amplifier and a variable complex load of a loudspeaker. The current is high and most amplifiers use feedback to improve their output quality. This requires a cable of low resistance, low capacitance and surely low inductance. This makes cable cooper hungry and (almost) impossible to screen. The lack of screen might affect the feedback circuitry.

    The higher capacitance of low inductance cables can make ‘tweako’ amps oscillate (sorry Naim users), but not other quality gear such as my Tag or Brystons. But let us not forget noise, either airborne or induced. Speaker cables are more susceptible as low impedance trails than interconnects, so they are intrinsically more susceptible to picking up RF, and inducing EM noise where they run near audio lines. They are not generally shielded, nor in long runs have the noise cancelling of a differential (balanced) line. Even an XLR is less susceptible to RF pickup than typical spade lug. And, depending on the RF atmosphere near your gear, the length of speaker cable sometimes turns out to be a near perfect aerial for the transmitted frequency.

    Based on the output impedance of my TAG AV32R, I can easily run 30m interconnects and not hear or measure any effect. I haven’t tested further but the calcs. indicate 100m might be possible.

    For quality cables (low inductance) Kimber is a great example, with VERY long lengths (if you can afford them) the differences would be tiny, certainly less than 1db which isn’t audible on test tones, let alone music. For ‘Siltechs’ etc, it gets really interesting with many other brands in between If your speakers have a weird resistance, and dip low, it gets worse again.

    With a pre-amps, it takes a really lousy cable to foul up things - with anything under 100 ohms output impedance will cause NO problems. My Tag is 50 and with a load of at least ten times that (which most amps easily exceed), you do not see any deterioration of the t-function for runs up to 30m or more, and often up to 100m for these ‘well designed amps’. I am sure there are better examples than my Tag AV32r processor, particularly in the stereo pre amp fold, but it what I have at home.

    If you hear differences look to plugs and soldering faults / poor manufacture / poor screening not the cable…..


    So after all that gunk what do cables need to do:

    Speaker cables: You want low inductance (EM theory) and lowish resistance.

    Interconnect: You want low capacitance. Resistance and inductance are much less a factor. You want good shielding.

    Video / digital: Low capacitance, linear CI, proper shielding and proper termination

    Mains: Low R, shielded / braided / twisted for RFI issues.

    Get these right and this is all you need to do
     
  20. NicolasB

    NicolasB
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    That's a bit of an oversimplifcation, isn't it? If the cable impedance (which, I suspect, is mostly resistive most of the time unless you do something stupid like coiling the cable) is high enough that it's a significant fraction of the speaker impedance, then it will be a significantly different fraction of the total cable/speaker impedance as the speaker's impedance varies with frequency. That means that the speaker's sound output will be relatively more attenuated at frequencies where the speaker impedance is low than it is when the impedance is high.

    Admittedly for the cable impedance to actually be that high represents a fairly pathological case, but it's not impossible if you're using long, thin wires. In cases like this bi-wiring helps a bit by halving the effective cable resistance.

    An interesting experiment for someone who thinks bi-wiring makes an audible difference would be to replace the speaker shunt and then connect the amp to one set of terminals using two lengths of speaker cable. If that sounds more like the bi-wired sound than the single-wired sound then I think you have your answer.


    Certainly true, but I was wondering if the process of laying unshielded speaker cables alongside one another when bi-wiring could introduce additional stray capacitance beyond what you see with each cable in isolation....
     
  21. Calle

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    Uhm.. how does that differ from biwiring? Isn't that exactly what will happen when biwiring?
     
  22. NicolasB

    NicolasB
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    Biwiring means running one length of cable to each pair of speaker terminals and removing the shunt. I'm suggesting running both cables to the same set of speaker terminals and leaving the shunt in place.
     
  23. Calle

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    Ah, I see. Yes, that would indeed be an interesting experiment. Anyone up for it? ;)

    I'm currently aiming for more obvious improvements, namely to get rid of a standing wave peaking at my sofa. :(
     
  24. pwiles1968

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    I did Bi-wire my B&W's anout two years prior to Bi-Amping them because I felt they were a little bright, I was getting some sibilance with certain artists Sheryl Crow in particular and IMO it did resolve the issue, I do not know why but I was happy. If nothing else it meant it was really easy to install my Mono-Blocks when they arrived, and did they make a difference!:eek:
     
  25. NicolasB

    NicolasB
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    Bi-amping can certainly produce real advantages. Bi-wiring is the one some of us are more sceptical about.
     

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