Reversing Polarity -- Voodoo or Easy Tweak?

Cwlondon wrote:

what happens?
and why do some recommend?

changing the polarity on BOTH speakers.

Although the "polarity" in this case changes, it does so on both speakers, the polarity remains consistent so the signal remains "in phase".

This is reversing Absolute Polarity (I mistakenly referred to this as Absolute Phase in an earlier post). In my experience, when the signal is in correct Absolute Polarity, the sound is somewhat fuller, and more complete. The stereo image will remain focused and centered just as when the polarity is maintained plus to plus, and minus to minus.

It's interesting to note that one manufacturer of equipment I own refers to this as Absolute Polarity, and another manufacturer refers to this as Absolute Phase. No wonder there's confusion!

Regarding your statement about the necessity of a test disc to hear correct phase, I don't believe the use of one makes the listener a less-than-self-respecting audiophile any more than the use of a tape measure makes a less-than-self-respecting carpenter. Frankly, for someone new to the hobby, which we all were at one time, a test disc can be an extremely useful tool. Futhermore, the Phase track on the Stereophile Test CD is a quick and easy way to double check for correct polarity (phase) without uncertainty or guesswork.

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

[url]http://home.bellsouth.net/p/s/community.dll?ep=334&fileid=1630988&groupid=56202&folderid=203789&curRec=5&folderview=thumbs&ck=[/url]

Herman, your next to last post was great. Back in the early 70s I owned a pair of 3way Wharfedale loud speakers. The woofers were 12". The bass always seemed to be a little light, lacking authority. I had read somewhere to check the polarity of speakers and make sure the drivers were wired correctly, in reference to polarity, was to connect a 1.5V D cell battery, momentarily, across the speaker terminals + to +, - to -. If the speaker polarity was correct the speaker cones moved forward. On the Wharfedale's, the cones pulled back, just the opposite as they should have. I reversed the speaker cable leads on both speakers and the bass was improved.