Speaker Test
Play a tone through the left, right or both speakers to check that each side works.
Speaker Polarity Test
Play the same sound through both speakers in phase and out of phase to hear whether one speaker is wired + to −. In phase should sound fuller and centered; if Out of phase sounds fuller, one speaker is probably reversed.
Lower your volume before starting, especially with headphones. Nothing plays until you press a button.
Press In phase, Out of phase or Alternate, then compare how the two versions sound.
In phase should sound fuller, centered between the speakers.
Out of phase should sound thinner and spread out. If it goes almost silent, your sound is mixed to mono. If it sounds the same both ways, your device may be playing only one channel.
Signal
Stopped
Runs entirely in your browser. Test results, audio and video never leave your device.
How to check speaker polarity
- Turn off sound enhancements, spatial sound and virtual surround, set the volume low, and sit midway between your speakers.
- Press In phase and listen for a few seconds. The sound should be full and seem to come from a point midway between the speakers.
- Press Out of phase. With both speakers wired the same way, the sound typically gets thinner, with less bass, and seems spread out or to come from the sides.
- Press Alternate to switch between the two every 2 seconds. The highlighted box and the status line under the Volume slider show which version is playing.
- Compare them. If Out of phase sounds fuller and more centered than In phase, one speaker is probably wired + to − on a pair of full-range speakers; soundbars and subwoofer systems combine the bass, so Out of phase loses bass there whatever the wiring. Under Signal, choose Low tone to compare the bass on its own.
- To stop, press the highlighted button again or press Stop.
What is speaker polarity?
Speaker polarity is whether a speaker's cone moves out or in for the same signal, which depends on how its + and − wires are connected. Two speakers wired the same way are in phase: their cones move together. If one is wired backwards, they are out of phase, and their sound partly cancels, so the bass typically gets thinner and centered voices lose their focus.
What in phase and out of phase sound like
| What you have | In phase | Out of phase |
|---|---|---|
| Speakers wired correctly | Fuller bass, and a sound that seems to come from midway between the speakers | Thinner bass, and a sound that is spread out or seems to come from the sides |
| One speaker wired + to − | Thin and spread out | Fuller and centered: the two versions swap |
| Mono output | Normal, from the center | Quiet or almost silent, because the two channels cancel |
| A device playing only one channel | Normal | The same as In phase |
How to fix reversed speaker wires
- Turn off the amplifier or receiver before you touch the speaker wires.
- Check both speakers. The + terminal is usually red and − black. Speaker wire marks one of its two conductors with a stripe, ridge, text or copper color, and that conductor should go to + at both ends.
- On the speaker wired + to −, swap its two wires at either end. The test compares the speakers with each other, so it cannot tell you which one is reversed.
- Check that no loose strands touch the other terminal, turn the amplifier back on and test again. In phase should now sound fuller than Out of phase.
- Wireless speakers, soundbars and all-in-one speakers usually have no speaker wires to swap. Turn off their sound effects and test again; if Out of phase still sounds fuller, contact the maker.
Why both versions sound the same or cancel out
When your sound is mixed to mono, the flipped right channel cancels the left one, so Out of phase goes quiet. If it sounds the same both ways, your device may be playing only one channel. Each is a setting or a feature of the device, not a fault.
- Mono audio is on. Windows 11: Settings > Accessibility > Audio > Mono audio. Mac: System Settings > Accessibility > Audio, then the setting that plays stereo audio as mono. iPhone: Settings > Accessibility > Audio & Visual > Mono Audio.
- A Bluetooth headset is in hands-free (call) mode, which is mono. Close apps and tabs that use its microphone, or choose its stereo output in your sound settings.
- The device has one speaker, as some phones and small Bluetooth speakers do. It may mix both channels, so Out of phase goes quiet, or play only one, so both versions sound the same.
What this test can detect
- One speaker wired + to −: Out of phase sounds fuller and more centered than In phase.
- Speakers wired the same way: In phase sounds fuller, with the sound centered between them.
- Sound mixed to mono: Out of phase goes quiet or almost silent.
- Processing, or a device playing only one channel: both versions sound the same or almost the same.
How it works
The page plays one sound to both channels with the Web Audio API: unchanged on the left, and multiplied by +1 (In phase) or −1 (Out of phase) on the right, which flips its waveform. Pink noise is band-limited to about 80 Hz to 1 kHz; Low tone is a 100 Hz sine. Nothing is recorded or measured.
Each switch fades the right channel to 0 over 20 ms and back over 20 ms, so it does not click. Alternate switches every 2 seconds. Volume starts at 40%; at the top of the Volume slider, each channel peaks at about −9 dBFS or lower.
Limitations
- It compares the left speaker with the right, judged by ear, and does not measure phase. If both speakers are wired + to −, both versions sound normal, so the test cannot detect it.
- Sound processing (DSP), virtual surround and speaker placement can hide the difference, so turn off enhancements and surround modes, and sit midway between the speakers. Soundbars, 2.1 systems and subwoofers with bass management combine the bass of both channels, so Out of phase loses bass whatever the wiring.
- Stereo only: it cannot check the center, rear or subwoofer channels of a 5.1 or 7.1 system, or a subwoofer's phase setting. For subwoofer checks, use the Bass Test.
- Bluetooth adds a short delay, so in Alternate the sound can change a moment after the highlight. Playback stops when the tab is hidden, for example when you switch tabs, and on iPhone when the screen locks.
- Keep the volume moderate. Out of phase has less bass, and if you turn it up to make up for that, In phase is much louder when it comes back.
Frequently asked questions
Does it matter if speakers are out of phase?
Yes. Where the sound of the two speakers overlaps, a reversed speaker cancels part of the other's bass, so music typically sounds thin and voices that should be centered sound vague. The inverted version is an ordinary signal at the same level as the in-phase one; keep the volume moderate. Swapping the two wires on one speaker fixes it.
Can it tell which speaker is wired wrong?
No. It compares the two speakers with each other, so it can show that one is reversed but not which one. Check the terminals of both: the marked conductor of each wire should go to + at both ends.
Why does Out of phase go almost silent?
Because the sound is mixed to mono somewhere. A channel mixed with its flipped copy cancels out, so a mono audio setting, a Bluetooth headset in call mode or a single speaker that mixes both channels makes Out of phase fade away. That is a setting or a feature of the device, not a fault.
Is polarity the same as left and right?
No. Left and right is which channel a speaker plays; polarity is which way its cone moves for the same signal. Swapped channels still sound full and centered. To check left and right, use the Speaker Test, or the Headphone Test for headphones.
Why do I hear nothing?
Usually another output is selected, or something is muted. Choose your speakers as the output in your sound settings, and check the volume, the mute key and whether the tab is muted. On iPhone, the page asks to play through Silent mode where the browser allows it, and other audio may pause. If nothing plays, turn off Silent mode.