How to use: Sit centered between your speakers (this test needs stereo speakers, not headphones, for meaningful bass results). Play both signals and compare: the correct wiring is whichever sounds fuller, bassier, and centered.
Test Signal
Correctly wired speakers: Signal A sounds fuller and centered, Signal B thin and diffuse. Reversed? One speaker's wires are swapped.
Bass weight
With the 110 Hz tone, in-phase speakers reinforce each other and the bass is strong. Out of phase, the waves cancel across the room and the tone nearly disappears at the listening position.
Center image
In phase, the sound forms a phantom image floating exactly between the speakers. Out of phase, it smears - the sound seems to come from everywhere and nowhere.
Fixing it
Swap the + and - wires on one speaker (at the amp or the speaker, not both). Then verify with our speaker balance test and a frequency sweep.
Speaker Phase FAQ
What does it mean when speakers are out of phase?
Out of phase means one speaker cone pushes while the other pulls, because the positive and negative wires are swapped on one speaker. The two speakers then partially cancel each other - especially in the bass, where both channels carry nearly identical signal. The result is thin, weak low end and a vague, hard-to-locate stereo image.
How does this phase test work?
The test plays the identical signal from both speakers twice: once normally (in phase) and once with one channel inverted (out of phase). If your speakers are wired correctly, the "in phase" version sounds fuller, bassier, and centered between the speakers, while "out of phase" sounds thin and diffuse. If it is the other way round, one of your speakers has swapped polarity.
How do I fix out-of-phase speakers?
Check the wiring at both the amplifier and the speaker terminals. Each speaker connects with a positive (usually red or marked) and negative (black) conductor - the positive amp terminal must reach the positive speaker terminal on both sides. Swap the two wires on ONE speaker (either end) and re-run this test.
Does phase matter for headphones?
Headphone drivers are wired at the factory, so phase problems are rare - but a damaged cable, bad solder joint, or faulty adapter can invert one side. On headphones an out-of-phase signal sounds strange and "inside-out": diffuse, hard to localize, with a hollow center. If the out-of-phase sample sounds more normal than the in-phase one, your headphones or cable have a wiring fault.
Why do I mainly lose bass when speakers are out of phase?
Cancellation requires the two sound waves to overlap while opposite. Bass wavelengths are several meters long, so the waves from both speakers stay aligned (and cancel) across your whole room. High frequencies have wavelengths of centimeters - tiny position changes break the alignment - so the treble survives while the bass disappears.