Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics.

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You will NOT see the same voltage across both sets.

Posted by Jon Risch (B) on June 2, 2007 at 21:19:07

In Reply to: You will see the same voltage across both sets. posted by clifff on June 1, 2007 at 06:48:34:

Yes, it would seem that you will see the same voltage at the ends of the two cables, but in reality, YOU WILL NOT. How much will this voltage differ?

By the amount that the impedance of the two different crossover sections differ vs. the finite impedance/resistance of the cables, and the amount of CURRENT flowing in each separate cable.

Due to the differing impedances of the two sections of a two-way crosover, the cable connected to the woofer section will see a lot of current at LF's, but very little at high frequencies, while the cable connected to the tweeter section will see some curent at HF's, but not very much at all for LF's.

This is due to the fact that the LF section will have a low impedance at LF's, but it will get higher and higher as the frequency goes up, while the HF section will have a low impedance at HF's, but it will get higher and higher as we go down in frequency.

I show this info, taken from a real speaker, at:
http://www.geocities.com/jonrisch/page9.htm

related pages are at:
http://www.geocities.com/jonrisch/biwiring.htm
http://www.geocities.com/jonrisch/biwiring2.htm
http://www.geocities.com/jonrisch/biwiring3.htm

So the people that argue that biwiring does nothing, because they are only thinking of voltages, are dead wrong, and really haven't given the matter much thought, or bothered to do some basic measurements.

The voltage differences will be on the order of fractions of a dB, with the yardstick being that a voltage difference that is 40 dB down from nominal will result in a 0.1 dB change in level. I have measured differences greater than that, and have provided evidence for sonic differences being relevant down to -90 dB below nominal, so there is a wide range of potential sonic differences that bi-wiring can be responsible for.


Jon Risch

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