How to run the phase test
- Sit in your usual listening spot, the same distance from both speakers, and set any balance control to the middle.
- Keep the volume low and press In phase. Both speakers play the same pink noise, and it should form one solid sound in the middle, between the speakers.
- Press Out of phase. The page now inverts the right channel, so its cone moves in whenever the left one moves out. The sound should lose its centre, spread wide or seem to wrap around your head, and get thinner in the bass.
- Press Alternate to switch between the two every 2.5 seconds. Hearing them back to back makes a small difference much easier to judge.
Reading the result
- In phase sounds solid and centred, Out of phase sounds vague and thin. Your speakers are wired correctly.
- It’s the other way round. One speaker is wired backwards, so the signal the page sends in phase reaches your ears out of phase. Rewire one speaker as described below.
- Both sound the same. Check on the left/right test that both speakers actually play, that you are sitting centred, and that nothing mixes the channels to mono. A soundbar or a single Bluetooth speaker can’t show the effect.
The difference is biggest in the bass. Low frequencies have long wavelengths, so the sound from the two speakers overlaps almost everywhere in the room: in phase it adds up, out of phase it cancels.
Fixing reversed speaker wires
Amplifier and speaker terminals are marked + and −, usually red for positive and black for negative. Speaker cable marks one of its two conductors so you can follow it from end to end. Yamaha’s wiring guide gives the common conventions, a red wire or the wire with writing on it for positive, and adds that makers use other markings too. It doesn’t matter which marking your cable uses, only that it lands on + at both ends of both cables.
- Switch the amplifier off before you touch any wire.
- Follow each cable from the amplifier to the speaker and check that the marked conductor goes to + at both ends.
- If one speaker’s wires are crossed, swap them at that speaker only.
- Switch back on and run the test again. In phase should now be the solid, centred one.
The battery check for a single speaker
When the terminals aren’t marked, or you want to check a speaker on its own, disconnect it from the amplifier and touch a 1.5 V AA battery across its terminals for a moment. Eminence, a driver maker, describes the rule: if the cone moves out, the terminal touching the battery’s + is the positive one. Watch the woofer, the largest cone; a tweeter barely moves. The listening test above has the final word, because it checks the whole chain as you actually hear it.
Subwoofers and other problems
A subwoofer’s phase switch or dial is a different adjustment: it lines the sub up with your main speakers around the crossover frequency. Set it with the subwoofer test. If one speaker sounds wrong rather than out of phase, with buzzing, rattling or missing treble, try the blown speaker test.