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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Bi Wiring?/co/Jon Risch posted by Ardy on March 24, 1999 at 20:08:16:
Ardy,Q is more or less correct with his power line analogy, as the distances and impedances involved scale closer to the power amp/speaker cable situatio than your battery and light bulbs. Most D cells or whatever, have a distinct output impedance, so the source voltage will drop at the batteries termianls, the short run of wire has the battery drop swamping the wire drops.
When you talk about the audio signal, it is compsoed of two parts, voltage and current. Dynamic (and other types) operate on the current passed through the voice coils in order to produce sound. Without the current,. there is no sound. If you look at the voltage in each cable, there are slight differences between what the woofer cable carries, and what the tweeter cable carries, due to the impedances of the cables themselves. These voltage changes are down around -48 dB from nominal (for a 14 gauge wire, approx. 10 feet long at drive levels of approx. 10W into 8 ohms), and represent IM distortion. Voltage fluctuations in the HF's can easily be two or three times that level, or 6 to 10 dB higher levels of IM distortion.
The current flow is very definitive, and the product of the voltage and the current, which is power, varies from the woofer cable to the tweeter cable.
See my web site, the specific page at:
http://members.xoom.com/Jon_Risch/page9.htmThere are two diagrams on this page, one is the single cable current flow through the wires, andnthe other shows the current flow through the separate bi-wired cables.
Note the distinctly different current flows in the two wires. Much more current is flowing at LF in the woofer cable than in the tweeter cable. This is due to the crossover input impedances, and is the reason that bi-wiring does do something.
Aside from the voltage drops, there are the magnetic fields to consider. By separating the LF currents from the HF currents, any tendency for the LF magnetic field to modualte the HF magnetic fields is reduced. How could a magnetic field of one frequency modulate another's? The cable effect commonly known erroneously as magnetostriction, or the action and reaction of the cable wires to transient magnetic fields causing the wires themselves to move, and hence intermodulate the signal, is responsible. High end cable manufacturers refer tot he resoancne, or lack of it, for there various cable designs,a nd this is where it comes into play.
Separate the LF and HF into flowing in two different cables, and the amount of this magnetically induced sign-song is also reduced. WHile this effect can still occur within each cable, it has been reduced by dividing the current load between them. Each bi-wire cable will now "sing" to it's own song that much less.
I would suggest you read the entire section on bi-wiring at my web site, and then if you have any questions, post them.
Jon Risch
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Follow Ups
- Re: Bi Wiring?/co/Jon Risch - Jon Risch 10:21:03 03/26/99 (0)
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