Stereo Test
Check that your speakers or headphones really play in stereo: a chime in the left channel, the right channel and the centre, a sound that pans across, notes that bounce side to side, a balance control to find the true centre and a phase check for wiring faults. The speaker icons light up with each channel.
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Channels
Stereo image
Set your system volume to about half, then press Left.
How to test stereo sound
- Turn your system volume to about half. Sit centred between the speakers, or put headphones on the right way round (L on the left ear).
- Press Left, then Right. Each should come only from that side; answer the question that appears for an explanation.
- Press Centre. With good stereo the sound seems to come from the middle, between the speakers.
- Press Pan left to right and Ping-pong notes. The sound should travel smoothly across with no hole in the middle.
- If the centre leans to one side, press Balance tone and move the balance slider until it sits in the middle. The number shows how far your setup is off.
What the results mean
Read the results like this:
- Left and right each from one side, centre in the middle: stereo works.
- Left and right both from everywhere: the output is mono. The mono test confirms it and shows how to switch Mono Audio off.
- Left plays on the right: the channels are swapped, usually speakers on the wrong sides or headphones worn backwards.
- Centre leans to one side: the system balance is off, one speaker is louder, or you are sitting off-centre. The balance tone tells you by how much.
- In phase sounds wide and vague, out of phase sounds focused: one speaker is wired with plus and minus reversed. Swap the two wires on one speaker.
Speakers vs headphones
On headphones, left and right are completely separate, so a left-only sound is in your left ear only. On speakers, both ears hear both speakers, so the effect is softer: left comes from the left speaker's direction rather than only one ear. That is why the centre sound appears to float between the speakers, a "phantom centre". If it does not, the speakers are not at the same distance or one is louder.
For speakers, place them at an equal distance from you, about as far apart as you sit from them, forming a triangle. Point them slightly towards your head. For a deeper check of headphones, including bass and polarity, use the headphone test.
Phones and laptops
Most phones only play stereo when held sideways, with the earpiece working as the second speaker; in portrait many sum to mono. Small laptops have two speakers close together, so the stereo effect is narrow, and some send both channels to one speaker. A single Bluetooth speaker is almost always mono unless it is paired with a second one. None of these are faults; they are limits of the device.
Common problems and fixes
Sound only comes from one side
Check the balance in system settings (Windows: Settings > System > Sound > device > Left and Right; Mac: System Settings > Sound > Balance). Push the plug fully in. Try other headphones to see whether the fault is the device or the computer.
Left and right are swapped
Swap the speakers or the cables, or wear the headphones the other way round. Some sound drivers have a channel swap option.
Both sides play everything
Mono Audio is on, or the device is mono. Turn it off in the accessibility settings and check with the mono test.
No sound at all
Click on the page first (browsers block sound until you interact), raise the volume slider and the system volume, and check the right output device is selected.
Frequently asked questions
How do I test if my speakers are stereo?
What is a stereo test?
What does out of phase mean?
Why does the centre sound not come from the middle?
Can I use the stereo test on a phone?
Is the stereo test safe for my speakers?
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