bi-wire - how does it work?

[DuallyDave]

My new RC-25 and RB-15 speakers have bi-wire capability, but I'm not clear on how it works. I think I understand bi-amp, seperate amp connections to seperate speakers in place of a crossover. Is the bi-wire similar, does it somehow replace the crossover with just one amp connection? Goodguys wanted to sell me a $120 cable to do this, but they said I could also use two seperate cables somehow. How would that work, sounds less expensive? I'm coming from a Denon 1905.

[scriven]

Hello and welcome to the forum!

How does bi-wire work? - Poorly in my opinion. (Just want to let you know where I stand so you can take the rest of my statements with that background in mind.)

The idea is to run 2 sets of cables between 1 amplifier channel and the speaker. Some claim that this allows the bass frequencies to travel along one set of cables without interfering with the high frequencies because they are going down the second cable. I have no idea how the electrons know which path they should take. So, it is like bi-amping, if you leave out the second amp and the active crossover.

I can see how you would think it is a fantastic, if not necessity, idea when you are selling $120 cables!

[DuallyDave]

Thanks for the reply. I also wonder how the electrons know which path to take, since there is no filtering of frequencies. When I was googling around, one place said to just use as fat a wire as possible, and forget the bi-wire. It all just sounds like a way for monster cable to make more money.

[boom3]

Classic bi-wiring requires a crossover with seperate inputs to the woofer and tweeter sections. A seperate cable is run from the amplifier to the appropriate input. Some speakers are set up for this with a jumper between the high and low sections to allow use of one cable.

I agree that it's snake oil, as are all exotic cables, regardless of brand. The best approach is to use an appropriate gage of ordinary, household wire, in one cable set, and be done with it. In my case I use 14 gage low-voltage outdoor lighting wire for runs up to 50 feet. With speakers as sensitive as my Corns, the gage of the wire becomes less critical, but 14 gage is the right combo of wire size and compatibility with the terminals on either end, via bannana plugs.

[dragonfyr]

Don't blame Monster for this nonsense!

After all, Monster had already developed their magical 'frequency balanced' cable where their educated electrons know which conductor to traverse!

...While the rest of us have had to rely on a silly thing called a crossover for all these years!

But I wonder...if you used the Monster 'frequency balanced' cable to bi-wire, would the electrons get confused by having so many choices to make? And would the transients suffer if they can't decide fast enough!? And if some of the dumber electrons can't decide fast enough will this result in a big electron traffic jam, and....oh dear! the potential ramifications are truely frightening!

If you insist on wanting to toy with something interesting, consider an extreme slope active crossover (or digital Xover) with time delay and bi-amplification.

[Mick Bell]

I tried bi-wiring just to see what all the fuss was about. Turned out it's about NOTHING. I couldn't tell one particle of difference.

Mick

[tofu]

i tried by wiring as well on my old rf-3's.

couldnt tell any difference either

[cmdridq]

"It all just sounds like a way for monster cable to make more money."

I think you're starting to understand bi-wiring pretty well.

[jheis]

It doesn't.

[J.4knee]

Yeah I will chime in too it is pure witches brew. It is a marketing gimmick.

[WMcD]

I think it has no advantages. This is just a tweeking fad without technical merit. Apparently the market demanded it and so Klipsch Inc., which had some relation with Monster Wire at the time, put in the extra terminals. Maybe it was Monster rather than "the market."

I believe there was technical misconception behind the tweek. It was that somehow the bass frequencies and the treble frequencies interact in the wire. This is not true. If it was true, channel 2 and channel 3, etc., in TV cable distribution systems would interact and interfere. Of course that does not happen.

To answer another question, in biwiring there is, in fact a filtering effect. Current at treble frequencies does only flow in the the pair connected to the treble crossover. Current at bass frequencies does only flow in the pair connected to the bass crossover.

So, you ask the age old question of engineering, "How does it know?"

We normally think of the bass, low pass filter, of not passing through high frequencies. And the treble, high pass filter of not passing through low frequecies. This is in fact correct.

These designs, though, also do not absorb frequencies outside their pass through range. I.e. the low pass filter has a high impedance to high frequencies. So current at high frequencies does not flow in the wire pair. The same is true of the high pass.

This makes sense in that there is a treble and bass driver (say each having an 8 ohm impedance) essentially connected in parallel to the amp through the respective crossover filters. Yet the overall system impedance is not 4 ohms. This is because the inputs to the respective filters turn on and off in their respective frequency range.

I used to take a harder line on what I consider technically worthless tweeks. Now I feel that if they are not expensive, it can be fun to fool around. I do cringe went someone spends a lot of money and announces remarkable results. This makes others follow in the footpaths and find the same placibo effect.

I understand that "placibo" in Latin means "I make you happy."

Best,

Gil

Best,

Gil

[dragonfyr]

Gil, with what you have said, have you had an opportunity to examine the Nyquist plots for various conductors either independently or in combination with the 'remaining' load. Such a detailed complex impedance mapping, along with the other correlative information provided by this view might indeed provide insight in to why certain total loads respond differently with of each source as opposed to simply looking at the 'nominal' impedance.

My gut feeling is that there is much to be found that might very well correspond to some perceived differences. It just might bring the two camps a bit closer together (although I would still not anticipate that the cables, provided the resistance is low, would make that great of a total difference...)

[WMcD]

No, I've never seen a Nyquest plot for wire alone, or in combination with the speaker load. (Why do I think you're testing me? Smile.)

I did do some quick calculations based on the Nyquest plot for the K-Horn input load which appeared in the Hyster review.

There is some interesting stuff to be inferred. You can see the effect of the drivers and crossovers. E.g. the woofer gets fairly resistive for most of plot in its frequency range. The mid comes on with much higher overall impedance with a big circle due to the autotransformer. Then the tweeter has a smaller circle showing lower impedance.

Of course the J values go plus and minus at various frequencies. You can use the normal equations to compute what amount of lumped inductance in the plus, or lumped capacitance in the negative, it would take to create these J values. They are substantial in the extreme cases. the extreme cases being the top and bottom of the circles.

We also have the resistive component (the right hand portion of the plot), which needs no back calculation to find a lumped equivalent.

On the other hand, we have wire runs with attendant capacity and inductance and resistance. People correctly say that wire has such qualities. But then they fail to compare them to the speaker load equivalents.

In all cases the speaker load impedances (resistive or reactive) are orders of magnitude greater than the wire. This is why E.E. types scoff at the notion that wire can have much effect on anything.

If you want, we can collaborate on cranking some numbers.

Gil

[Duke Spinner]

Same for Damping factor ...

high numbers look great ...

untill you figger in the speaker voice coil ...

[dragonfyr]

With regards to cables being a determining criterion for a system, I agree that if their resistance is sufficiently low, and with allowances for a few valid exceptions, the cables are negligible as regards the total response of the system.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

More significant would be the Nyquist response of the speakers. But in any regards, if one is going to evaluate a particular system response, both the cables and speakers should be evaluated as a total unit constituting the actual load.

But if there are differences in response, I suspect that these differences would be apparent in the complete impedance plot indicating a detailed frequency dependent reactance view as well as the correlation within several simultaneous domains that the Nyquist provides, and any actual differences would be able to be seen here.

A classic example of this is the interaction between the total source and load interaction as the Source (amp) too has a complex impedance. And, for instance the combining of an amplifier that is capacitive in the first few octaves would not be as suited to driving low frequencies as that of an amplifier that is inductive at the low frequencies.

What I am suggesting is the power of these measurements to add to the understanding of both from the component as well as the system view, for both design and regarding an increased correlation between measurements and listening.

Simplistic flat static measurements such as nominal impedance and its treatment of the time and frequency variant differential behavior as if is a constant provides some useful guidelines, but falls well short of explaining its complex behavior.

With the increase in the availability of the tools to provide both Nyquist and Heyser spirals and transfer functions of components and systems, these become increasing desirable tools for both design and analysis.

And it is my desire to begin acquiring these for the primary Heritage and Reference speakers, as well as other significant acoustic measurements for the general use by those with a need for them.

Oh, and Duke, I agree with your general assessment, but with significant exceptions! With traditional dynamic drivers this is generally true, assuming a relatively greater acoustic cone loading (damping). But in other driver types, and in dynamic drivers in configurations such as bass reflex or infinite baffle when approaching tunings near their free air resonance, as the acoustic loading (damping) decreases, the electro-mechanical damping increases in significance. So it is of value to define our frame of reference, as what is negligible in one circumstance may not be negligible in another!

[Petrol]

bi-wire - how does it work?

As far as I am concerned, it works great for the manufacturer, store & salesman who all seem to have found a way to increase sales without having to have gone to the trouble of finding new customers...marketing victory.

as for, "...Apparently the market demanded it and so Klipsch Inc., which had some relation with Monster Wire at the time, put in the extra terminals..."

I have to admit my ignorance here, I was under the impression that the "extra-terminal" were provided for Bi-Amping?