Speaker test

Press Left while wearing headphones or sitting centered between your speakers. The sound should come only from your left side. If it comes from the right, the channels are swapped — on headphones check you are wearing them the right way (L and R are usually printed on the band or the ear cups); on speakers swap the cables at the amplifier or in your operating system balance settings.

Usually because the output is mono. Windows has a Mono audio accessibility switch, macOS has Play stereo audio as mono, and iOS and Android have a similar option under accessibility. Bluetooth headsets in hands-free (call) mode also drop to mono, and a single laptop or phone speaker cannot separate channels at all. Turn mono off, or test with headphones.

It plays the same noise to both speakers twice. In the in-phase version both speakers push and pull together, so the sound is solid and seems to come from a point between them. In the out-of-phase version the right channel is inverted, which sounds hollow, wide and thin in the bass. If the version labeled in-phase is the one that sounds hollow, one speaker has its + and − wires reversed.

The full sweep glides a pure tone from 20 Hz to 20 kHz so you can hear where your system starts and stops producing sound, and whether any note makes something rattle or buzz. The bass sweep covers 20 to 200 Hz for checking a subwoofer. Small laptop and phone speakers often produce almost nothing below 100 to 150 Hz, which is normal. The top end also depends on your ears: most adults stop hearing somewhere between 12 and 17 kHz.

At sensible volume, yes. Start with your device volume low and raise it gradually — pure tones can sound much louder than music at the same setting, and very high frequencies can be loud even when you can barely hear them. Avoid running the bass sweep at high volume through small speakers, which can damage them. Every sound stops the moment you press Stop.