Bi-Wiring, yes, again.

Discussion in 'Audio Hardware' started by Katz, Aug 29, 2019.

  1. timind

    timind phorum rezident

    If I had an oscilloscope handy I would post a pic of the signal waveform presented to each speaker binding post. The signal would be identical at both the tweeter and woofer binding posts. I'd love to have someone here prove me wrong.
     
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  2. Ingenieur

    Ingenieur Going with the flow...

    Location:
    PA
    You have been proven wrong.
    By Q Acoustics, they did EXACTLY that.
    But no need, the math already did.


    Conclusion

    We have discovered that if your speakers have four binding posts then you may take advantage of the bi-wiring option and that you will need twice as much cable as before. We theorised and proved by measurement, the counter-intuitive notion that the high and low frequencies travel only in their designated cables. We have also shown by measurement that the theory that this would reduce intermodulation distortion caused by non-linearity in the speaker system is proven.
     
  3. Ingenieur

    Ingenieur Going with the flow...

    Location:
    PA
    O-scope current probe measurements
    Signal generator
    Single cable at speaker
    Bi-wire high freq tweeter cable at speaker
    Bi-wire low freq woofer cable at speaker

    based on Kirchhoff and math it is impossible for the bi-wired signals to be the same.
    The measurements confirm it.

    [​IMG]
    [​IMG]
    [​IMG]


    [​IMG]
     
    Last edited: Nov 22, 2020
  4. Bolster

    Bolster If it ain't broke try harder..

    Location:
    UK
    Awkward... :rolleyes:
     
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  5. timind

    timind phorum rezident

    Not really. The images posted by @Ingenieur show current, my post referenced signal. I quoted @Bob_in_OKC's question which I interpreted as whether the signal was the same at each binding post.

    Of course the signal flowing through each driver will be different, the crossover ensures this. But, the signal presented to each crossover is identical.
     
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  6. Ingenieur

    Ingenieur Going with the flow...

    Location:
    PA
    A 'signal' is comprised of V and I (the product of which is power) at a given sum of frequencies.

    wrong
    The current will be different but the signal the same? That is absurd.
    The signal IS current!
    The reason the current/signal is different is that hi or lo freqs are attenuated by their respective xover.

    in the graphs are different because their 'signal' is different by attenuation of freqs, as is clearly illustrated. It is graphed signal/current amplitude vs freq.

    what parameter would your O-scope measure
    V
    I
    'Signal'
    Power
    ???
     
  7. Ingenieur

    Ingenieur Going with the flow...

    Location:
    PA
    In electronics and telecommunications, (a signal) refers to any time varying voltage, current or electromagnetic wave that carries information.
     
  8. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    If you had an o'scope handy you could prove it to yourself. But since you don't have one, you can carry on believing that the current in each cable somehow magically remains the same despite their differing loads.
     
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  9. timind

    timind phorum rezident

    I'm not talking about the current flowing through each cable, I'm talking about the signal as represented at the output of the source compared to the signal at the output of the amp and also at the input to the speaker. I'm talking about a standard oscope probe which is different from a current probe, and doesn't measure current. With a standard probe, the waveforms would be identical. I get @Ingenieur's point, it's not how I interpreted the question.

    I'd also say that if Q Acoustics wanted to prove their point, they would've provided the results after taking the same measurements at the input to the respective crossovers using single wire with the shorting straps in place. Not difficult to do.
     
  10. Bolster

    Bolster If it ain't broke try harder..

    Location:
    UK
    Meanwhile, the wag that resurrected this thread yesterday is lying low and about to watch a movie with a side order of scotch.. play nicely chaps :D
     
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  11. Ingenieur

    Ingenieur Going with the flow...

    Location:
    PA
    the 'signal' IS current!
    You obviously have no education in the subject.
    But that is OK.
    Bear in mind it takes the same knowledge to derive a correct answer as it does to recognize an incorrect one.

    What variable does your 'standard' scope probe measure? V? I? ????
    What are the unit of measurement?
    It must measure a physical, observable, measurable parameter.

    The I of the 'signal' and the V will BOTH
    be different at the end of cable/speaker input terminals. Since Z is different and V = I Z

    And the signal at the amp/beginning of each wire will be the same as at the end/speaker input terminals. They MUST be or violate every principle of physics.

    BUT the signal (V, I, P) will be different in each wire.

    if I is different, and Z is different, V must be different, hence power is different.
    The high cable will have attenuated lows
    The low cable attenuated highs
    PERIOD

    Q Acoustics proved their point (reality).
    It was the PERFECT test set-up.
    What you propose is pointless.
     
    Last edited: Nov 22, 2020
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  12. timind

    timind phorum rezident

    My last go at this. Q Acoustics proved the current flowing through a cable is dependent on the load provided by the circuit. They proved the obvious. If Q Acoustics wanted to prove their thesis, they would've measured the input to to the crossover when wired with single wire and straps in place. It would've taken all of 30 minutes to setup. If they had a dual trace scope, they could've run the test simultaneously and shown the differences in real time. How does this not make sense?

    Also, when I say the signal doesn't change, maybe I should've used the term, waveform. That said, I'm talking about measuring the signal with a standard scope probe which measures the signal's amplitude and frequency. It won't measure the current. If we remove the biwire cables from the speaker binding posts and measure the waveform, both cables will measure the same. When we hook the cables to the binding posts, the amplitude and frequency of the waveform will still be the same. That is how I answered the question originally. If you don't agree with this...well I don't know what to say.

    I will admit it's been 30 years since I've worked with any of this, but I'm confident everything I wrote above is correct. Especially the fact the only thing Q Acoustics provided proof of is current flowing through the tweeter's circuit and the woofer's circuit is different. Thanks, and have a good holiday week.
     
  13. Ingenieur

    Ingenieur Going with the flow...

    Location:
    PA
    wrong on every count:
    Q Acoustics measured the signal at the end of the wire/at speaker input, not AFTER the filter, but BEFORE.
    Single and bi-wired and the difference was attenuation of freq. Simple and elegant, proved their hypothesis. Period

    The waveform changes, that is what they measured.
    The hi cable has attenuated lows
    And vice versa
    Semantics
    Signal
    Waveform
    Current (hence V since there is Z)
    Are ALL THE SAME THING

    the signal (I, V, etc.) is different in each cable
    Period

    What you need to say is you are wrong but ego or lack of knowledge precludes it.

    You never answer questions:
    -what is your scope probe and what variable does it measure, the ones I posted were magnitude vs freq. what is yours?

    -What accounts for the difference in current in their test? And why were the low and hi freqs attenuated?

    I have a MSEE and design filters.
    One application is for VFD's. The inverter section produces harmonics that travel into the power source and load. These are currents, they have a waveform, you could call them a signal but since they convey no information not appropriate.
    We filter to attenuate the harmonics the free up line capacity for useful power, not harmonic garbage.

    It is the EXACT same principle, science and engineering.
    Peace
     
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  14. Ingenieur

    Ingenieur Going with the flow...

    Location:
    PA
    The reason I am insistent is that I do not want misinformation spread for those considering this. Can you hear the difference? That is up to the listener.

    But if the signal is the same in each wire there is no reason to do it. You would achieve the same by upsizing wire and using the jumper.

    And all the engineers at KEP, Focal, etc. wasted there time and $ building speakers that can be bi-wired. But I'm guessing they did it for a proven technical reason.
     
  15. vinnn

    vinnn Forum Resident

    Location:
    England
    You've made the classic mistake of thinking an amp pushes current out to a speaker, it doesn't. Current flows towards the negative terminal like water flowing downhill to ground. The current or signal on the wire is determined by the characteristics and load of the speaker driver so in a bi-wire scenario each wire ends up carrying a different signal, doesn't matter at what end of the wire you're looking at.
     
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  16. Ingenieur

    Ingenieur Going with the flow...

    Location:
    PA
    An amp is a variable voltage source.
    The current is determined by the load I = V/Z
    The load varies with frequency

    You can look at a speakers Z magnitude and phase chart to learn about it.

    The Z at low freq is different than at high end
    This due to the filters
    Low being Z ~ freq, as f increases so does Z
    Hi being Z ~ 1/freq as f increases Z decreases

    the magnitude is in Ohms
    The phase in degrees, the ratio of L and C reactance to R (arctan of)
    When 0 degree all R
    At these points C and L reactance are equal and cancel.
    As degrees go negative L is in play, lo pass
    As phase goes positive C is in play, hi pass


    [​IMG]
     
  17. George P

    George P Notable Member

    Location:
    NYC
    Can you explain what L, C and R stand for here? Is it length. capacitance and resistance?
     
  18. Ingenieur

    Ingenieur Going with the flow...

    Location:
    PA
    L inductance, related to the magnetic field in Henries
    C capacitance, electric field in Fareds
    R resistance in Ohms

    L and C have to be converted to get Ohms
    That value is reactance
    Xc = 1/(2 Pi f C)
    Xl = 2 Pi f L
    Where
    Pi = 3.141596..,,
    f = frequency in Hz
    you can see these are freq dependent

    Z impedance magnitude in Ohms =
    sqrt(R^2 + (Xl - Xc)^2)
     
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  19. AJM2021

    AJM2021 New Member

    Location:
    Leeuwarden
    I am a producer and not a believer in bi-wiring. Most manufacturers even don't have multiple connectors for the reason that it isn't really a thing.

    Simple experiment for the bi-wirers. Take B&W, they have kind of golden strips at their backside. It automatically connects the midrange to the tweeters. Now disconnect those and replace it with two cables that run to the amp at the same connector. The effect should be identical as having those attachers in place. Now hook them up to the inputs for speaker 1 and 2 apart and you can switch the midrange and the tweeter on by a press of a button. Where speaker 1 and 2 fulfills the same function as the strips..

    Bi amping is a thing but a third really audible thing is experimentation. This way you can create cool own soundstages. For example hook up a speaker with amazing treble to a speaker which has good mids but lacks treble. On a real bookshelf you can put a set of treble speakers on a higher shelf and a set of mids lower.
     
  20. Vaughan

    Vaughan Forum Resident

    Location:
    Essex, UK
    Well, I have read all of this thread, and understood at least half of it. That's my bad and the result of not paying attention in class.

    I am on the verge of buying some new speakers, and they allow for bi-wiring. More interesting, perhaps, they're from Q-Acoustics, which is purely coincidental.

    I am curious about bi-wiring, and since the speakers I might get will be new, I won't be A/Bing things as such, I'd simply initially set them up with, or without, bi-wiring.

    My situation is simpler than most here, it seems:

    1) I could not care less about having to use more cable. I make my own, and have a reel of the stuff. No additional outlay then.
    2) I have a single amp (Sony STRDN1080). The manual of this amp is clear that you can bi-amp using just it. I have read the arguments about the single power supply, but while that may not be ideal, I don't really see why it would be the be-all and end-all of the argument. Optimal? Probably not, but it's also not the arbiter of better/worse sound as far as I can tell.
    3) Since these are new speakers, I won't be able to tell if there's a difference or not. I could A/B with and without, but I'm not sure why I'd bother once they're in place.
    4) I'm more concerned about doing damage to the sound, ie. making things worse. I've not read anything that suggests this could be the case. At worse, it's the same, right?
    5) The differences in opinion are telling. It tells me that whatever the outcome, it's not "night and day", and may well vary between combinations of speaker and amp.
    6) Q-Acoustics have three ranges of speakers, let's call them A, B, C, with price rising up. The newest model of type A have removed the b-wire option, having previously had it.

    I am a little lost in the argument. I have seen one person suggest it was all a scam by manufacturers to sell more cable, which sounds like one of those old conspiracy theories. Hi-fi sellers will always try to sell you expensive cables, be they bi-wire (two sets of cables) or not (one set of cables). Paul at PS Audio tells it like this: Back in ye old times, before we had high end cables, the cables used were either really good with bass signals, or really good with higher frequencies. There was nothing in between. So a compromise was always made with single posts. Then someone hit on the idea that if you had two sets of posts (bi-wire) you could use the cables that were good for bass to the woofers, and use the cable that was good for higher frequencies to the tweeter, thereby improving sound. However, this is no longer the case, and today's cables have largely done away with this distinction. Paul states that he no longer bi-wires his own gear.

    The fact we don't have consensus is probably telling too. Clearly there is space for debate. I don't see this as a deal breaker though. If I buy speakers with two sets of posts, then the only additional cost is the cable, which as I say, is not an additional cost for me. The science is interesting, but I can be easily led in that regard due to my own ignorance.

    Still, there is the argument that, if bi-wiring does nothing, why go to the additional fuss? That's harder to say. I guess I was hoping for a more "open and shut case", but alas, I'm not going to get it, am I? A part of me says, if this was an obvious upgrade, it would have been well accepted by now. In fact, I went to Youtube and tried to find some videos on the subject, and amazingly there is very little information on there (which, of course, isn't important, but is surprising). The information there is is largely (the vast majority actually) about the basic mechanics of it, rather than an science or reviews of results. Perhaps that's also telling giving the broad depth of content on a site like that.

    I don't know where that leaves me on the subject. I've done a search here, and it seems there are more arguments that people really testing different configs and coming back with an opinion. So I guess this remains a grey area.
     
  21. Vaughan

    Vaughan Forum Resident

    Location:
    Essex, UK
    Wasn't sure whether to make this post as an edit, or as a separate post. I've read the Q-Acoustics article, and my simple brain has trouble understanding it. To be specific, these two paragraphs seem key, since it's the basis of the argument:

    "Consider the above circuit before the amplifier provides any potential at its output terminals. The traffic jam will be stationary – it’s nose to tail trucks and motorbikes all the way from the amp, down both speaker cables, inside each of the LF and HF networks and back to the amp again. Nothing is moving. Suddenly the amplifier gives the green light. In the HF network are a set of bollards too close together for trucks to get through – only motorbikes can slip through. So in speaker cable 1 only the motorbikes will be moving. Yes, the trucks are still there but they are all parked – can’t move. In electrical terms only high frequency currents will be flowing in speaker cable 1. Even though the filter circuitry is at the far end of the cable there will be no low frequency current present in the whole of the cable leading up to that point. This is a hard concept to grasp first time. If you get it great, read on. If not then keep re-reading to this point until you do.

    The same goes for speaker cable 2, except in the LF network there is 2 foot six feet of water which the motorbikes cannot negotiate so they are all stationary, whereas the trucks can plough on through. So, in speaker cable 2 only the low frequency current will be flowing. Effectively, as if by magic, we have separated the high and low frequencies and sent them down different cables to the correct driver. If you are still asking “but how do the different frequencies know which way to go?” or saying “ don’t talk rubbish, both cables have all the frequencies in them the same, right up until the crossover” – then try re-reading the above until you understand it."

    This is all well and good, but it presents more questions. If I take what they're saying literally, then something is filtering those signals. They call them "bollards" and "2 foot 6 of water", but for me they're filters of some kind. Yet the article - to me simple brain - doesn't address this. Meaning, it's not specific about what these filters are, and how they work. They seem to gloss over this. In other words, okay, so there are bollards - what are these Bollards, and where are they located? In the amp? In the speakers?

    I hope that makes sense............
     
  22. frimleygreener

    frimleygreener "It 'a'int why...it just is"

    Location:
    united kingdom
    I solved all these dilemmas by purchasing loudspeakers with just one pair of binding posts.
     
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  23. F1nut

    F1nut Forum Resident

    Location:
    The Mars Hotel
    You have an AVR not an amplifier. As such it's basically a 20lb. weakling rated at 165 W (6 ohms, 1 kHz, 1ch driven THD 0.9%). That's only one channel driven at one easy frequency with a fairly high THD. The more channels driven the less wpc it will be able to produce. Forget bi-amping, which actually is impossible with an AVR anyway.

    As for bi-wiring, changing the el-cheapo plated stock jumpers to high quality speaker cable is a much better idea.
     
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  24. Vaughan

    Vaughan Forum Resident

    Location:
    Essex, UK
    I am aware of the debate of stereo reproduction from an AVR. I was aware of this when I bought it (I do have stereo amps too, but not for this usage). However, the truth is, I very much enjoy Surround music, so I have little choice. Besides, despite what the naysayers might say, Stereo sounds pretty damn good. That said, I'm not pretending it's high end.

    As for whether bi-amping is impossible on an AVR, I'm merely going by the manual which states:

    "When the front speakers are Bi-wire speakers, which are equipped with separate terminals for high-frequency sounds (tweeter) and low-frequency sounds (woofer), you can make the biamplifier connection. Connect each pair of terminals for tweeter and woofer to the SPEAKERS FRONT A terminals and SPEAKERS SURROUND BACK/HEIGHT terminals of this receiver. You can enjoy higher quality sound playback if you operate the tweeter and woofer using separate amplifiers."

    In context, "separate amplifiers" is referring to the same AVR, but different connections. So I don't know what to say.............
     
  25. Jack_Straw

    Jack_Straw Forum Resident

    Location:
    Wichita, KS
    I have my 5.1 surround system hooked up exactly this way - using a Yamaha RX-V667 AVR. I’m currently using B&W DM601 Series 1 speakers for my front channels, and there is a noticeable improvement with the bi-amping on them (I did have to recalibrate my speaker levels for 5.1, since those two speakers are louder than they were without the bi-amp setup.). I tried it with my previous speakers (Energy bookshelfs), and the opposite was true. While I did notice the bass and low mids became tighter and more detailed, there was too much brightness and harshness added to the top end, so after a week or two I reverted back to the conventional setup.

    So my advice is - try it both ways and see what you prefer. My receiver handled it just fine, and one set of speakers did and one didn’t. YMMV.
     
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