Reversing Polarity -- Voodoo or Easy Tweak?

Herman...Agreed that terminology is commonly sloppy. However, "OUT" of phase means a shift of 180 degrees, which is the same thing as a polarity reversal.

Audiophiles like to worry a lot about the phase shift introduced by filters, as in a crossover network, but, as the phase shift increases beyond the break frequency, the amplitude decreases, so that phase becomes irrelevant.

If ONE speaker has + and - (it's polarity) reversed, then the system will be "out of phase".

Their polarities are reversed, they are not out of phase. However, this description (out of phase) is so deeply ingrained that I should just give up on it. As pointed out, Stereophile uses it as do many manufacturers. I had a Conrad Johnson CD player with a "phase" switch when it was really a polarity switch.

Herman...Agreed that terminology is commonly sloppy. However, "OUT" of phase means a shift of 180 degrees, which is the same thing as a polarity reversal.

No it's not. With a symetrical waveform it is impossible to tell by looking on a scope whether a signal is inverted or 180 degrees out of phase, but musical signals are asymetrical so there is a difference. The usual example is a kick drum that is struck once and then damped. The intial wave that strikes your ear is a compression followed by a rarefaction. If you reverse polarity then it is a rarefaction followed by a compression. This is a big difference. If there was a phase shift then you would still get compression then rarefaction but earlier or later than what it should be.



Waveform A is of equal but opposite polarity to B. They start at the same time but one starts out going positive and the other negative. Waveform C is 1/2 cycle(180 degrees) out of phase with A because it starts 1/2 cycle later. As Eldartford points out, there is no difference between B and C once they get started, but this is because they are symetrical.

Waveform D and E are also equal but opposite polarity while F is phase shifted from D. There is a big difference in E and F whereas B and C appear to be the same. The kick drum (point kd) on waveform D will initially push the speaker cone out while on E it will suck it in.

Some say this all makes no difference in sound, but they are different.

When I said "equal but opposite polarity" I meant equal amplitude but opposite polarity.

If the picture doesn't show up here is the link

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To be a total stickler for terminology, speakers CANNOT have their polarity reversed, since they are driven by AC, which has no + or - poles! Only DC has a + or - polarity. Speakers can have only an absolute phase inversion [both speakers have the wires reversed on the + and - terminals], out of phase [only ONE speaker wire will have the + and - terminals reversed...very bad indeed!], or have a phase shift. A phase shift occurs when different frequency ranges are shifted [delayed] by milliseconds. This can be due to crossovers, physical driver alignment, speaker wires, or the amplifier powering the speakers. Sort of like a prism splitting white light into the various frequencies of colored light...in effect, a rainbow. Again, not good. But phase shift is pretty much a fact of audiophile life. The amount of phase shifting will determine the coherency [or not] of the sound.

FYI, here's a neat trick to get raw drivers in phase when the terminals are not marked or marked incorrectly [it does happen!], or for car installations where multiple long concealed speaker wire runs can easily be installed out of phase. Take a "D" cell battery, and hold the speaker wires to the battery. Note whether the speaker cone moves out or in. I consider "out" to be the + terminal and "in" to be -, this being a good memory aid.