Speaker Polarity & Phase Test
A polarity test plays the same sound twice: once with both channels in phase, once with one channel inverted. When wiring is correct, version A sounds full and centered and version B sounds thin, wide or "inside your head". If it is the other way round, one speaker is probably wired backwards.
Before you start
Turn your volume down before you start. Stop if anything is uncomfortable. Long exposure to loud or high-pitched sound can damage hearing.
These tests need JavaScript to make sound. The explanations below work without it.
Sound starts only when you press a button, at a low level with a soft fade-in. The level is capped in the code. Esc or the space bar stops it. On iPhone, turn off silent mode or web sound may stay muted. This is not a medical hearing test.
Polarity / phase test
Play both versions. Which one sounds fuller and more centered?
Press a button to play.
Which sounded fuller and centered?
How to fix speakers out of phase
- Turn the amplifier off.
- On each speaker and on the amplifier, find the + (often red) and − (often black) terminals.
- Make sure + goes to + and − goes to − on both speakers. Cables usually have a stripe or text on one wire to help.
- Turn on and run the test again.
Sit centered between the speakers, or use headphones. On headphones a polarity fault is rare, so the test mostly shows what out-of-phase sounds like.
Frequently asked questions
What does out of phase sound like?
Thin, with weak bass, and as if the sound is coming from everywhere or from inside your head instead of a clear point in the middle. Version B on this page lets you hear it on purpose.
Why does polarity matter?
When one speaker moves out while the other moves in, low frequencies partly cancel. You lose bass and the stereo image becomes vague. Fixing the wiring brings both back, and voices return to a clear spot in the middle.
Can headphones be out of phase?
It is rare but possible with a faulty cable, a repair or an adapter. If version A sounds thin and B sounds full on headphones, try another cable or device.
What if A and B sound the same?
You may be listening on a mono speaker or with mono audio on, in which case B can sound much quieter. Check that you hear two separate channels in the left/right test first.
Is phase the same as polarity?
Not exactly. Polarity means a signal flipped upside down; phase is about timing shifts. For speaker wiring, people often say "out of phase" when they mean reversed polarity, which is what this test checks.
Last updated: October 13, 2026