In reply to:
Is induced currents a bad thing concerning speaker cables?
Yes. It is unwanted current flow that will go through your speakers, and come out as noise, and NO speaker wires (and the signals inside of them) are rarely, if ever the CAUSE of induced voltage.
I think you asked something other than you meant, though.
The audio signals flowing through the speaker wires are very small. They also do not repeat the same cycles over and over again, so any magnetic fields and the voltage created by them created by them will be very random, very small, and will not result in a steady flow.
A 120 volt AC signal is really 169 volts when you measure the sine wave from peak to peak. The 120 volts is RMS, or Root Mean Square. This is the measurement used for any time varying signal's effective value: It is not an "Average" voltage and its mathematical relationship to peak voltage varies depending on the type of waveform. By definition, RMS Value, also called the effective or "heating" value of AC, is equivalent to a DC voltage that would provide the same amount of heat generation in a resistor as the AC voltage would if applied to that same resistor.
This 169 volt AC signal goes from 0 volts to just about 85 volts and back to 0 volts in the first 1/2 cycle, and then it goes down to -85 volts and back up to 0 volts in the next 1/2 cycle. It does this 60 times per second. Each time the voltage goes up, a small magnetic field builds up around the power cord. As the voltage goes down, the magnetic field collapses again. Then the signal goes to the negative side, and a magnetic field builds up with the lines of force going around the power cord in the opposite direction. As the voltage goes back up to 0 volts again, that field collapses, and the cycle repeats. Inside of that power cord, there is NO induced voltage. The up and down swing of the voltage matches the polarity swing of the magnetic fields building up and collapsing ( "fluxing" for you "Back To The Future" fans
). They tend to cancel each other out.
So how does this affect audio? It doesn't. UNLESS you lay your speaker wire inside of the magnetic field that is always building up and collapsing around the power cord. Why? That speaker wire is supposed to contain 100% pure audio signal. If you lay the speaker wire ALONG SIDE OF your power cord, those magnetic fields also surround the speaker wire. As those fields build up and collapse, they move the electrons in the speaker wire causing the unwanted current to show up as a 60HZ buzz coming out of your speakers when no music is playing. When music IS playing, these voltages can just plain out mess with the audio signals in the speaker wires by adding and subtracting voltage from the audio signal.
There are 3 ways to avoid this.
#1 -
always run you speaker wires
across, but not
next to your power cords. This way, the magnetic lines only "cut" into the speaker wire at a very small section, and they also do it perpedicular to the wire instead of parallel to it so no current is induced. (Any car buffs out there know that this also applies to spark plug wires as well for the exact same reason.)
#2 - Twist up the wire inside of the power cord, which "randomizes" the directions at which the fields are created (think helix). Doing so creates many small fields in many directions, and prevents them from causing any induced voltages large enough to matter.
#3 - Keep the speaker wires and power cords at least 6" apart - far enough to keep the magnetic fields away from the speaker wires altogether.
Oddly enough, it is the exact opposite use of magnetic fields that make the speakers work in the fist place, so go figure... Too much of a good thing, no?
