Science explanation for biwire

michaelgb

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Leaving the "it works" "it dosent work" arguments aside ,,,

Whats the science behind bi-wiring ? i honestly dont understand how its supposed to work if the cable terminations are connected together at amp.

 

Clubsport911

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People used to talk about seperating ground currents, but as we all know, they end up at the same transistor. Mission produced a whitepaper (I recollect) with some details...

 

gjm

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It's important to know exactly what is being discussed. If taking two wires from the output terminal of the amp, and attaching them both to the same speaker binding posts, then there is nothing to be gained other than a lighter wallet. If taking two wires from a single amplifier output terminal, and connecting the other end to different binding posts on the speaker, then there could be a difference by virtue of bypassing the crossover.

And then there is the altogether much more complicated subject of using multiple amplifiers to independently supply power to individual drivers within a loudspeaker system.

http://www.achievum.eu/bi-wiring.html

http://www.achievum.eu/bi-wiring.html - scientific investigation discussed.

http://www2.audioquest.com/wp-content/uploads/2012/02/UndrstndgBiWr.pdf

And bi-wiring & bi-amping discussed: http://www.chuckhawks.com/bi-wire_bi-amp.htm

 

HoopsOnToast

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It's important to know exactly what is being discussed. If taking two wires from the output terminal of the amp, and attaching them both to the same speaker binding posts, then there is nothing to be gained other than a lighter wallet. If taking two wires from a single amplifier output terminal, and connecting the other end to different binding posts on the speaker, then there could be a difference by virtue of bypassing the crossover.And then there is the altogether much more complicated subject of using multiple amplifiers to independently supply power to individual drivers within a loudspeaker system.

http://www.achievum.eu/bi-wiring.html

http://www.achievum.eu/bi-wiring.html - scientific investigation discussed.

http://www2.audioquest.com/wp-content/uploads/2012/02/UndrstndgBiWr.pdf

And bi-wiring & bi-amping discussed: http://www.chuckhawks.com/bi-wire_bi-amp.htm
But you are not bypassing anything in the crossover when Bi-Wiring in that description.

 

Beobloke

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As I have mentioned before, to me, the chief benefit of bi-wiring is to be able to experiment with different cables for the bass and treble sections. I have some old Heco bi-wire speaker cable and it uses different core constructions for the two runs it contains. It definitely sounds better one way round compared to the other.

I would concur that using two lengths of the same cable seems a little self-defeating.

 

browellm

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As I have mentioned before, to me, the chief benefit of bi-wiring is to be able to experiment with different cables for the bass and treble sections. I have some old Heco bi-wire speaker cable and it uses different core constructions for the two runs it contains. It definitely sounds better one way round compared to the other.I would concur that using two lengths of the same cable seems a little self-defeating.
Isn't the point that the since the crossover electrically sees one cable, all you would be doing is presenting a slightly different combined LCR value to the speaker?

 

HoopsOnToast

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No, if you do it as Adam suggests, the LCR value would be different (if you used very different cables) for the bass and treble sections of the crossover rather than exactly the same LCR value if you used the same cable for both runs.

Hence why you might hear a difference but thats only down to radically changing the speakers originally designed response. Sort of like a L-Pad on either the tweeter or bass.

Bi-Wiring using the same cable makes no difference.

Bi-Wiring using two different cables can make a difference.*

*(but its likely that it not what the original design intended, although may sound better to you)

 

gjm

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But you are not bypassing anything in the crossover when Bi-Wiring in that description.
That's what I thought.
Sorry - to clarify, you would start with a speaker with - say - two pairs of binding terminals which, when connected to an amplifier with a single wire, are connected using a jumper (cable or plate).

When biwiring, this jumper would be removed. This could bypass a crossover.

Does that make more sense? I know what I mean!

 

Monstrous

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Sorry - to clarify, you would start with a speaker with - say - two pairs of binding terminals which, when connected to an amplifier with a single wire, are connected using a jumper (cable or plate).When biwiring, this jumper would be removed. This could bypass a crossover.

Does that make more sense? I know what I mean!
If the speaker is passive, you can't bypass the crossover unless you connected the amp directly to the drive unit. Do you mean you're splitting the speaker signal in the crossover rather than outside of it? I wouldn't imagine that makes any difference at all.

Bi-wiring is something I really don't understand the point of. All you do is split the signal from one pair of outputs at the amp end, to give you the detriment of running twice the amount of cable.

 

HoopsOnToast

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I posted this before, and the ATC speakers are good as they have a nice layout on the crossover:

ATC SCM10 - Single wired (no biwire)



IMAG0088 by RSdesignUK, on Flickr

This has the treble and bass crossover sections seperate but paralel on the single pair of inputs.

This is the SCM20 - Bi-Wire (same board, layout as the SCM10)

crossover.jpg


If you single wired the SCM20 crossover and used jumpers, it would be exactly the same electrically as the SCM10 crossover above.

When Bi-wiring you don't bypass any of the crossover.

 
C

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Does it improve the sound simply because the brass links on some speakers were taken out of the equation ( so to speak) ? Or is that a load of tosh.

 

Radford Revival

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Bi-wiring in the case of passive speakers barely even has an edge case use that I know of, it's completely pointless. It actually makes things worse (to a minuscule degree given typical cable impedances) around crossover points. This is easy to demonstrate by calculation or measurement.

So you can either have the performance of a single cable, or slightly worse, with twice as much cable.

 

Radford Revival

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Please do :pop:
Here's the electrical sum of a simple 2nd order 1Khz LR (Q=0.5) crossover fed via an ideal 0Ω impedance:

Zero-impedance.png


Here's the same network fed with a source impedance of 1Ω (ie an exaggerated cable length). As the network becomes more reactive around the crossover point there's a small lift (or rather, lack of attenuation) of around 0.5dB.

Single-wire.png


Here we have each half fed with the same but separate "cable", giving a slightly worse departure of around 0.7dB from flat around the crossover point.

Bi-wire.png


Obviously this is a contrived example and like I said the differences in real life would be tiny / irrelevant. Each portion of the crossover cannot directly provide electrical damping to other portions directly at the speaker terminals, but through two whole lengths of cable. The point is that broadly speaking, if anything bi-wiring has a slight disadvantage over a single cable.

 

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