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Is biwiring worth it?

Discussion in 'Home Cinema Speakers' started by ADC, Jan 16, 2005.

  1. ADC

    ADC
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    I have the possibility of Bi-wiring my front L&R speakers and want a bit of advice.
    1. Is it worth the extra outlay? I have QED xt350 (i think) on the front three speakers currenly so would obviously look at using the same.
    2. Would it be worth using some cheaper cable (silver annivesary) for all front three as opposed to buying the more expensive QED?
    3. Is it worth it at all?????????
    Thanks in advance :smashin:
     
  2. Knightshade

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    Hi ADC,
    As a quick test (If you have any spare cable lying around) remove the jumper plates on the back of the speakers and run some cable between them instead. If you (Honestly) hear an improvment then leave it that way. If you don't, then don't waste your money.
    Bi Wiring is essentially this but with longer cable.
     
  3. Beastie Boy

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    Knightshade,

    I don't know a lot about bi-wiring, but I thought the idea was that seperate cables carried the high and low frequency signals. Doing what you suggest would mean the signals shared a common cable right up to the speaker terminals, which is exactly what ADC already has.
    How does replacing the jumper plates with speaker cable make any difference? It'e electrically the same.

    ADC: Don't waste money on expensive cable regardless of what you decide. As long as the cable has a reasonable CSA (cross sectional area) ie, big enough, then I doubt you would notice any improvment.

    Cheers, Beastie.
     
  4. Knightshade

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    Hi Beastie Boy,
    The theory is that the wire is of a better quality than the gold plated tin that often comes with speakers.
    As you have stated if the wire has a good enough cross section then why bother?
    If you are running a single amp the hi and low frequency will travel together no matter how many cables you have, all you do is increase the cross section of cable.
    A single run of good cable is all you need.
     
  5. Beastie Boy

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    Agreed, but because the speakers have filters/crossovers built in to seperate the hi's and lows, then each cable would only carry high frequncy or low frequency current. The signal presented to each cable would be the same, but filtering at the speaker would only allow currents within a specified frequency range to pass through.

    I currently have a similar quandry. I intend to run my speaker cable under the carpet and so it needs to be low profile. Obviously it also needs to be of reasonable size.
    I have considered buying flat 4 core x 1.25mm sq bi-wire cable due to it's low profile. The question is would I be better off pairing 2 cores together to make 2 x 3 mm sq or would it be better to use it in a bi-wire configuration?

    Any advice?

    Cheers, Beastie.
     
  6. Knightshade

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    Again, I doubt you'd be able to tell the difference :)
    You would get rid of the jumper plates and it would make life easier to Bi amp in the future apart from that just try and get the highest gauge wire you can.
    Check the cables forum for useful advice.
    Cheers
    Knight
     
  7. Mason @ B&M

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    Bi wiring shouldn't make any difference, I've not seen any evidence to the contrary.

    Knightshade is spot on with this comment:
     
  8. richjthorpe

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    I have a pair of Mission 773es that I have biwired to a Denon AV and now currently to a Rotel amp. Both amps have the option to output a second set of front speakers or remote speakers. I hooked up the bass drivers to the main terminals and used the second/remote terminals to deal with the highs. I must say, the difference was incredable ! Sound had much more clarity.

    In terms of biwiring to the same terminals at the amp, I haven't done tests myself but I have read up on it and have to say that I agree with Beastie Boy on the physics but cannot comment in the real world. To get better quality you must run a second set of cables from the amp.

    Richie.
     
  9. Mason @ B&M

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  10. Beastie Boy

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    I've read the link posted above, but it still seems to come down to opinion and the fact that overall cable size is increased by doubling up. I would like to know if there is any scientific merit in my comment posted above.

    It seems to make sense but I have never read anything about how bi-wiring works without bi-amping and whether or not 1 larger conductor is better than 2 small ones or vice versa.

    Cheers, Beastie.
     
  11. Mason @ B&M

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    Say you have dual binding posts with the connector bar in place so they're not bi-wired. If thats the case then the connector bars send a full range signal to both the high and lowpass sections of the crossover.

    After the passive the signals have not been split, they've been attenuated by the crossover slope (6db, 12db per octave) but they are carrying the desired frequency ranges.

    Now if you consider a bi-wired signal, you're not actually changing the circuit, all you are doing is removing the connector bar at the speakers and moving it to the amps speaker cable terminals as they are internally connected.

    It's the same circuit...

    Bi-amping is different and better yet is running fully active crossovers prior to the amp stage.
     
  12. ADC

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    Thanks for clearing that up for me :eek:
     
  13. Reiner

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    So much for the theory, but is there any proof that this makes an audible difference?

    There is no difference in the wiring, see below.

    That's what I concluded, too, i.e. bi-wiring is the same as doubling the diameter of the cable:
    Assuming you have a 2.5mm2 cable and now add a 2nd 2.5mm2 cable to bi-wire it's the same as replacing the existing 2.5mm2 cable with a 5mm2 cable.

    If you leave the metal plates in place or not when adding a 2nd run of cables does not make a difference either, impedance-/resistance-wise it doesn't change anything.

    Exactly!
     
  14. Beastie Boy

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    But is it..

    If we apply basic electrical principles, the current flowing in each cable is determined by 2 things (assuming both cables are the same).
    1) the source that each cable is connected to ie. the amp terminals.
    2) The connected load ie. the speaker coils.

    In our case the source is common, it has to be as both cables are connected to the same binding post on the amp, therefore each has the same input prestented to it.

    However, the load on each core is different. In a bi-wiring configuration, each cable is connected to a different coil playing a different frequency range. Therefore the current will not be the same in each cable.

    If we look at this in a different context...
    Think of your consumer unit/fuse box/distribution board at home. each circuit connected to it has the same source ie 230V at 50Hz. All cables are connected to a common point.
    As in the example above, all the outgoing circuits have different currents flowing eg the cable feeding the kitchen with the kettle switched on has a higher current than the cable feeding a table lamp in the lounge. The difference is the connected load in each case.

    Taking it a step further, if we connected the 2 circuits together at the load end ie. a ring main circuit then yes, both current would be the same.

    The same applies in our bi-wire quandry. Non-bi-wired is the equivalent of a ring circuit, bi-wired is the quivalent of 2 radial circuits.

    The real question, as has already been mentioned, is does it make any audiable difference?

    Cheers, Beastie.
     
  15. Mason @ B&M

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    Yes it is the same circuit, both cables are connected to the amp, so both cables are connected to both speaker coils.

    All you do with bi-wiring is add extra cable.

    You're describing bi-amping not bi-wiring.
     
  16. Beastie Boy

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    No it isn't :)

    Consider a double socket outlet in your home. If you plug a kettle into one side and a lamp into the other, then both cables will have different currents. You wouldn't say that each cable is feeding both appliances just because they were both fed from the same socket.

    With bi-wiring, each cable is connected to a different driver and become two discreet circuits, each feeding a load independant of the other. Just because they are connected to a common source does not mean that the currents in both are the same, as illustrated in the example above.

    The advantage with bi-amping is that each driver may have it's source adjusted independant of the other and so the sound may be finely tuned to the preferance of the listener, and each amp is feeding a smaller load. But again, we have two disceet circuits feeding 2 discreet drivers.

    I hope I'm not rambling to much. Are there any other electrical type people out there that can vouch for my theory, even if it makes bugger all difference in practice ;)

    Cheers, Beastie.
     
  17. Mason @ B&M

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    I don't want to be argumentative but you're simply not right...

    The amps have a common +ve and -ve connection, so the cables are connected at that point. Which means both cables are connected to both drive units.
     
  18. Mason @ B&M

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    OK lets think of it another way, the signals get attenuated in the x-over so they feed the right frequencies to the drivers.

    At the point where the cables meets the crossover they contain a full range signal, thats both pairs if we're looking at biwiring.

    Then the x-over attenuates the highs and lows accordingly.

    --------

    Tell you what here's a way to prove it.. :)

    Remove the wires going into the tweet section of the biwire. Make sure your amp is turned off and wire a 1.5V battery across the cables you've taken off the tweet bi-wire...

    Your midbass will excurt a couple of mm and stay there..

    Then tell me the circuit isn't connected ;)
     
  19. Beastie Boy

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    Are you saying that even if the shorting plates are removed, then the cables are still connected inside the speaker? What you were suggesting earlier is that the point of common connection is at the amp, not the speaker.

    I'm assuming that any speakers capable of bi-wiring have seperate filters for the highs and lows so that the circuits remain discreet throughout. You're suggesting that even with the shorting plates removed, both cables feed together into one x-over/filter. Surely that can't be right or why would the manufactuers go to the bother of providing two pairs of binding posts :confused:

    Cheers, Beastie.

    PS. I don't find this argumentative at all :) I like a good debate. :D
     
  20. Beastie Boy

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    I just found this info on the B&W site which backs up what I was saying about each cable feeding seperate loads.

    I'm still don't think it would make enough improvement to the sound that I could honestly tell the difference.

    Cheers, Beastie.
     
  21. Mason @ B&M

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    The best way to understand this is to draw the circuit out, you'll see that no active components are changed, just the lengths of cable used.
     
  22. Reiner

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    This is all correct but from the amp's point of view it makes no difference - the load, and hence the sum of the currents, will be the same (ignoring the resistance of the cables).
    Different currents in each cable does not necessarily equal any benefit - a standard 1.5mm2 copper cable can easily carry the currents (and frequencies) of a hifi or AV system.

    Correct again, but as above the current drawn from the fuse box (or the energy supplier if you like) is the sum of all currents. There is no benefit except that you avoid overloading of each circuit - but overloading is not an issue in our case.

    That is correct, too, but it's bi-amping and thus the benefits (if any) are not comparable to bi-wiring.
    In fact some people claim that instead of bi-amping one should opt for a better or more powerful amp to get the same result, but this might be a topic for a different thread.

    The difference between a normal speaker and a bi-wiring one is that the x-over can be split - which means nothing but that the wiring does not remain on the PCB, instead is jumpered to the terminal where the metal bars connect high- and low pass.
    Of course both passes, and thus the filters, will be disconnected / separated from each other when you remove the plates.

    Looking at this from the amp's point of view (and that's from where we should look if we expect to find anything) there is no difference however, the electrical circuit and load remain the same, only the connection point between low and high pass is shifted from speaker terminal to amp's terminal.


    If you want to do it right you have to do like it's common in car-audio systems:
    Take an active cross-over, dedicated amplifiers for each pass (high- and low) and rip out the x-over from the speaker so that the amps' output connects directly to the drive units. :)
     
  23. Beastie Boy

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    Thanks for the input Reiner.

    Yes, I agree that from the amps point of view, bi-wiring would make no differance and the connected load remains the same regardless. I think this is where the confusion may be arising. Looking from the amps point of view, both circuits are the same, just as plugging the kettle and lamp on the same circuit makes no differance to the load on the consumer unit. But this doesn't mean both circuits are electrically the same.

    With bi-wiring, we are not trying to prevent overloading on one of the cables, but to keep different frequency current apart to try to prevent harmonics from one circuit having an adverse effect on the other. Let me try and give an example.

    Say we are playing a 2kHz tone in a single wire configuration. This would be sent to the high frequency driver when it reached the speaker. Now suppose that at this particular frequency, the driver produces a 80Hz harmonic wave. This frequency being induced onto the cable, if of sufficient amplitude, could be enough to drive the bass cone to play this frequency and hence colour or taint the resultant sound.

    Now, if the speaker is bi-wired, the induced harmonic frequency is confined to the high frequncy circuit only, and cancelled out at the amp terminals. Thus it never reaches the bass cone.

    The same applies for harmonics generated by the bass circuit. They remain isolated from the other circuit.

    This is the whole point of bi-wiring. To keep the 2 circuits on a seperate feed and prevent one colouring the other. I'm sorry if I'm not explaing myself very well.

    Now the reason I'm not convinced that any practical advantage can be heard is because an audio waveform (unless it is a test tone) has a constantly changing frequency, and so any resultant harmonics would also be constanly changing and of a very short duration.

    This is making my head hurt. I never did like studying harmonics. :)

    Cheers, Beastie.
     
  24. Knightshade

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    Hi Beastie,
    Been a away for a while and quite surprised to see this thread still going strong!
    I see what you're saying but either the speaker cross over or the amp will stop the wrong frequency reaching the driver. The question is where is it best to have this happen?
    My feeling is it won't make a blind bit of difference where you have it happening. In physics yes but audibly no.
    Interesting though, I don't think I've ever heard anyone argue so convincingly for Bi Wiring.....:)
     
  25. Mason @ B&M

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    I see what you're getting at :) But I don't see why the amp would stop the induced harmonics from reaching the bass driver unless the amp output channels were seperate (bi-amping again).

    I'm going to go talk to some uber techies and ask them to comment on this ;)
     
  26. Beastie Boy

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    Thank you! Thats my whole point. Theoretically, what I am saying is correct. But does it make any audiable difference? I doubt it, but I'm not able to test myself as my speakers are not capable of bi-wiring (and I probably wouldn't bother if they were).

    Cheers, Beastie.
     
  27. Beastie Boy

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    I would love to hear what they say. I must admit, when it comes to harmonics, I feel I am on shaky ground as far as my knowledge and experience goes :thumbsup:

    I believe the harmonics would be suppressed at the amp terminals due to the fact that the voltage at this point is fixed, wheras a 80Hz harmonic wave for example would be allowed to pass directly from cone to cone. To be honest, I I'm not 100% sure of this particular aspect. I'm looking foreward to learning somthing here.

    Thanks for bearing with me throughout this debate.

    Cheers, Beastie.
     
  28. pragmatic

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    One point that should be remember is that even though most amps have an A-B speaker set, i.e. two sets of connectors for each speaker, these connect to the same amp.
    So although you have have 4 physical binding posts per speaker the two set are connected to a single amp.

    left A
    \ _ Left Amp
    /
    left B

    So the current ect.. drawn will be the same over both cables (as the sum of the possitives and negatives are all that the amp cares about), the only difference that could be made is if one cable was capable of delivery bass or treeble better than another. (do such cables exist?)
    In which case you would use the best cable for the job, but then again as the source is constand and the sum of +/- would change this would change the properties anyway.

    I think that bi-wire is more about deliveing a thicker cross section of wire, using two lengths rather than using one thick length.

    Bi amping has benifits but does bi-wireing? it's probably all psychological but if it sounds better to you no matter what the course does it matter?
     
  29. Beastie Boy

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    Some manufacturers do in fact claim this, I personally have my doubts however.
    Another thought along similar lines, just as a speaker cone can deliver cleaner mid-range if it isn't also trying to play deep bass at the same time, would a speaker cable deliver a cleaner high frequency signal if the bass was on a seperate cable?

    Probably not but just a thought.

    Cheers, Beastie.
     
  30. Beobloke

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    Whilst i can see that bi-wiring does not electrically change the circuit from amplifier to loudspeaker, surely you're not getting any benefit from it if you use the same type of cable to connect to each driver?

    I personally am convinced of the merits of bi-wiring, but as far as i can see the main benefit of it is to allow one to use a cable with a good treble response for the tweeter and one with a good bass response for the woofer, which is exactly what i had on my old system.

    Adam.
     

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