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Headphone Polarity Check

Find out whether one of your channels is wired backwards, by ear.

Which version sounded solid and centred, between your ears?

How this test works

Two versions of the same low tone are played. In version A both channels carry the identical signal; in version B one channel is inverted. In a correctly wired system A sums in the middle and sounds solid and centred, while B cancels there — losing the centre image, thinning the bass, and seeming to come from outside your head rather than between your ears. If B is the one that sounds solid, then the signals had to be flipped to sum correctly, which means one of your channels is already inverted somewhere in the chain. The tone is low-mid content because cancellation between channels is most audible where the wavelength is long relative to the distance between your ears.

What the results mean

A sounded solid
Correct. The two channels are in phase with each other.
B sounded solid
One channel is wired backwards. You lose the centre of the image and most of the bass.
No difference
The test could not reach your ears as intended — most often a mono output somewhere in the chain.
Absolute polarity
Reported as not testable. Only the relationship between the two channels can be heard.

Common problems and fixes

Both versions sound the same
Something is summing to mono — a single Bluetooth speaker, or the mono audio accessibility setting. Try wired headphones with mono audio switched off.
The difference is very subtle
Expected on speakers. Room reflections fill in the cancellation. Headphones make it unmistakable because each ear hears only its own channel.
B sounds solid — what do I do?
Check the speaker wire polarity at both ends, red to red and black to black. A single swapped pair is the usual cause and takes seconds to fix.

Frequently asked questions

What does out-of-phase sound like?

Hollow and diffuse, with no clear centre and noticeably less bass. On headphones it seems to come from outside your head rather than between your ears, which is the easiest way to recognise it.

Can this detect absolute polarity?

No, and nothing that works by listening can. Inverting both channels together is indistinguishable from inverting neither — only the relationship between the two channels produces an audible effect.

Does polarity actually matter?

Between channels, yes and substantially: opposite polarity destroys the centre image and cancels bass, which is most of what you notice about a stereo system. Absolute polarity is a much subtler question and is inaudible in most material.

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