The red is usually positive in almost all audio equipment.
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Typically Red is HOT in an electrical circuit. In audio, Red is considered Hot and the Red from the amp should be connected to the red for the speaker, UNLESS your amp, or Pre-amp Inverts the Phase, then you want to connect the red to black and black to red to correct the inversion of phase from the upstream component.
It doesn't matter, so long as you connect positive on the amp to positive on the speaker and negative on the amp to negative on the speaker. Kind of like jumping a car battery, but less dangerous if you mess it up.
If you do mess them up, it can sound bad. I have no idea why. Since the signal is AC, it's negative voltage some of the time and positive voltage some of the time, so it shouldn't make any difference. But I have heard them connected wrong and for some reason it does sound terrible.
Since the signal contains positive and negative values, the speaker is SUPPPOSED to suck in some of the time and push out the other part anyway. Speakers don't just move from neutral/zero to some positive distance from the voice coil. They also move backwards just as much. That's my understanding anyway, based on the fact that the signal doesn't favor plus or minus (otherwise it would be a combination of DC and AC).
Picture a bass note of 40 Hz with no overtones. A pure, repeating cosine wave. While it's above 0 volts, it's pushing the speaker. While it's below it's pulling. If you were to switch polarity, all you'd be doing is inverting the waveform. So it's still pushing and pulling. The only difference is you start off in the opposite direction. So for 1/80th of a second at the beginning it would be different. And somehow this makes an audible difference!
There must be more to it...
Hook up an electric bass cab backwards and see exactly what I mean. I worked with a bass player who did exactly that and the cab sounded pretty crappy until we re-wired it back to the proper polarity..."el sucko wrongo a mundo"...lower output, weird sound, and all of his fellow musicians pointing at him and laughing (not really as he was/is a very good bass player).
What Achilles said, and to add to that: The thing you don't want to do is hook one speaker one way and the other speaker the other way. Then when one is pushing the other is pulling, hence "Out of phase."
Hooking both "black to black / red to red", is 100% the same as hooking both "black to red / black to red"
I believe you guys are making that stuff up.
Ha! We're still here. At least I am. Maybe you've all been replaced by duplicates...
I switched the red and black on my secondary stereo, a Marantz CD63SE, a Pioneer receiver, some old Infinity SM speakers, and some Monster cable. I played Beck's Sea Change. I couldn't tell the difference between black to black and black to red.
Not particularly conclusive, but if I had heard a difference in this system I would have assumed it would be even more apparent in my main system.
I was not able to switch the polarity on my bass amp; the speaker is connected by a plug.
I'm afraid my guitar amps' speaker connectors are too fragile to mess with.
So until I have the patience to try this on my main rig I remain convinced the "polarity" of this AC signal makes no difference.
Yes, I meant AC in the general sense of the signal in the speaker cable having positive and negative voltages, not in the sense of a power cable. This was my point initially, that since the signal in the speaker wires is AC, revolving around zero volts, that it doesn't matter which way it's plugged in red-to-black and black-to-red or red-to-red and black-to-black.
Sorry, I don't think I'm describing this well. And full disclosure: my degree was in electrical engineering, so I ought to be able to be clearer. Like most engineers, I need to draw a diagram to explain my point, which doesn't work well on a forum like this.
I have a long weekend coming up. I'll see if I can repeat the experiment on my better system then. I've only put this off because my Audio Magic speaker wires are thick and unwieldy and my binding posts are so close together on my speakers that I have to be careful red doesn't touch black. (I'm not skeptical about the impact of zero impedance!)