# Speaker Test: Left/Right Stereo and Headphone Check

> Check your speakers and headphones online: left, right and center channel tests, a 20 Hz–20 kHz frequency sweep and an in/out-of-phase polarity test.

Canonical page: https://controllertests.com/speaker-test/

Play sound on the left, right or both channels, sweep the full frequency range and check speaker polarity.

**Interactive tool:** this page hosts a free test that runs locally in the visitor's web browser (no install, no upload). To use it, open https://controllertests.com/speaker-test/ in a browser on the device that has the hardware attached.

## What the speaker test checks

Stereo audio carries two separate channels. The **Left** button sends sound only to the left channel and **Right** only to the right; **Center** sends the same sound to both, so it should seem to come from directly in front of you (or from the middle of your head on headphones). If Left plays from the right side, your channels are swapped. If Left and Right both play from both sides, something is mixing them to mono.

The **frequency sweep** glides smoothly from 20 Hz (very deep bass) to 20 kHz (an extremely high whistle). People are commonly described as hearing roughly 20 Hz to 20 kHz when young, with the upper limit falling with age — so not hearing the top of the sweep is normal. The sweep is also a quick way to hear rattles, buzzing or a frequency where the sound suddenly drops out. The **phase test** checks speaker polarity: if one speaker's wires are reversed, bass partly cancels out and the stereo image becomes vague.

## How to use the speaker test

1. Turn your system volume down, then set the slider here to a comfortable low level. Increase gradually.
2. Press **Left**, then **Right**. Each should play only from that side. Press **Center** and check that the sound seems centered.
3. Switch the signal to **pink noise** if a tone is hard to place — noise is easier to locate, especially on headphones.
4. Run the **frequency sweep** and listen for rattles, distortion or silent gaps.
5. Compare **In phase** and **Out of phase**. In phase should sound fuller and more focused.

## Fixing common problems

- **Left and right are swapped:** check that headphones are on the right way (look for L and R markings), swap the speaker cables or plugs, or check the left/right setting in your audio software.
- **Both buttons play from both sides:** turn off “Mono audio” in your device's accessibility settings, check the balance slider, and make sure the output isn't a single mono speaker.
- **Only one side plays at all:** reseat the plug fully — a half-inserted 3.5 mm jack often plays one channel — and try another cable or port.
- **In phase sounds hollow:** on wired passive speakers, swap the + and − wires on one speaker only, then test again.
- **Crackles or distortion:** lower the volume, then check cables, connectors and Bluetooth interference.

## Method and limits

All sound is generated in your browser with the Web Audio API — there are no audio files. Channel tests use a `StereoPannerNode` set fully left, fully right or centered; the phase test feeds identical pink noise to both channels, inverting one side for the out-of-phase version. The sweep is a sine wave whose frequency rises exponentially, so each octave takes the same time. The level meters show what the page sends to each channel, which confirms the routing inside the browser.

The page cannot hear what your speakers actually produce — it has no access to a microphone — so your ears do the judging. Bluetooth headphones and speakers also add delay (often a noticeable fraction of a second), which doesn't affect this test but can put audio out of sync with video and games. Surround systems may route center sound to a dedicated center speaker.

## Browser and device support

| Platform | Supported | Notes |
| --- | --- | --- |
| Chrome, Edge, Firefox (desktop) | Yes | Uses the selected system output device |
| Safari (macOS, iPadOS) | Yes | Sound starts after your first click or tap |
| iPhone (any browser) | Yes | Turn off silent mode; built-in speakers are stereo in landscape on most models |
| Android browsers | Yes | Some phones have a single speaker — use headphones for left/right |

## Frequently asked questions

### Why does the left channel play from both speakers?

Usually because something is mixing stereo to mono: an accessibility “Mono audio” setting, a single built-in speaker, a mono Bluetooth speaker, or audio-enhancement software. Turn those off and test again with headphones.

### How do I know my headphones are on the right way?

Press Left — the sound should come only from the ear cup marked L. If it comes from the right ear, you are wearing them reversed or the channels are swapped somewhere in the chain.

### Is the frequency sweep safe for my ears and speakers?

Yes at sensible volumes. Start low: high frequencies can sound piercing and very low ones can make small speakers rattle. Stop the sweep with the button or `Esc` at any time.

### Why can’t I hear the highest frequencies?

Sensitivity to high frequencies naturally declines with age, and many speakers and earbuds roll off near the top of the range. It is normal for the sweep to fade out well before 20 kHz.

### Does this work on phones?

Yes. Many phones only have stereo speakers in landscape, and some have a single speaker, so use headphones for a reliable left/right check. On iPhone, make sure silent mode is off.

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_Last updated: 2026-10-01_