Reviewed 19 September 2026Quick answer: place two speakers in their normal listening positions, set the volume low and play In phase, then Out of phase, without moving anything. A stable center image and fuller low-frequency sound during the matching comparison can support a wiring check, but this browser test cannot identify which cable or component is reversed.
Stereo comparison
Compare in phase and out of phase
Start with the device volume low. Each button plays a quiet 200 Hz tone for three seconds through the currently selected stereo output.
Ready. Lower the volume before the first comparison.
No microphone access. The comparison does not inspect wiring or grade the result.
How the comparison works
Both buttons generate the same 200 Hz sine wave in the browser. The in-phase button sends matching waveforms to the left and right channels. The out-of-phase button reverses the right channel's polarity. It requests no microphone permission and does not listen to the room.
This is a controlled listening comparison, not a detector. Speaker distance, room reflections, device processing, Bluetooth links and the listening position can change the perceived difference.
How to compare a stereo speaker pair
- Turn the device volume down and confirm the browser is using the intended stereo output.
- Place both speakers where you normally use them and sit between them. Do not move the speakers between plays.
- Play In phase once at a quiet level, then play Out of phase at the same level.
- Listen for the location of the sound and the relative fullness around 200 Hz. Repeat each comparison once if the difference is unclear.
- Confirm any suspected cable problem with the equipment maker's instructions or a technician before changing connections.
What you may hear
In phase sounds centered and fuller
That is the expected comparison for many correctly connected stereo pairs from a centered position. It supports, but does not prove, matching polarity through the playback chain.
Out of phase sounds wider or less centered
That difference shows that the stereo output preserved the inverted channel. The exact effect depends on spacing, the room, the speakers and your position.
Out of phase becomes very quiet
The output may be mono or combining channels before playback, so matching signals with opposite polarity cancel. Check system mono-audio settings and the selected output.
Little or no difference
Try a centered listening position and verify that two separate channels are active with the left and right speaker test. A phone's single speaker or closely spaced drivers may not create a useful comparison.
Headphones and phone speakers have limits
Headphones present one channel directly to each ear, so the out-of-phase option may feel spatially different but does not reproduce the same acoustic cancellation as two speakers in a room. A phone may use one speaker, closely spaced stereo drivers or signal processing that reduces the distinction.
For basic routing, missing-channel or buzz checks, use the headphone test or the general speaker test. This page does not measure frequency response, delay, sound pressure or hearing.