Stereo Speaker & PhaseTester
Quickly and safely test left/right channel output and phase
of your audio equipment directly in your browser.
100% Safe Local Processing
This tool uses the Web Audio API to generate sound directly on your device. No audio data is ever sent to external servers, ensuring your privacy is completely protected.
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About Stereo Speaker Tester
The "Stereo Speaker Tester" is a utility tool that allows you to instantly check if the left/right (L/R) outputs of your earphones, headphones, PC speakers, or car audio are working correctly from your browser.
In addition to simple L/R checks, it features a "Phase Check" to ensure your speakers are wired correctly (+ and -). By playing an out-of-phase sound, you can detect unnatural sound spread or cancellation caused by wiring mistakes.
All audio is dynamically generated locally using the Web Audio API, so there is no need to install apps or download files. It consumes no data traffic and can be used safely and quickly.
How to Use
Check the Volume
Before starting the test, set the volume slider to an appropriate (low) level. This prevents sudden loud playback and protects your ears and equipment.
Check L/R Channels
Click the "LEFT (L)" or "RIGHT (R)" button to ensure sound is only coming from the specified speaker (or earphone). This helps check if the wiring is reversed.
Check Phase (Polarity)
Play "In-Phase" and "Out-of-Phase" alternately. If wired correctly, in-phase sound comes from the center, while out-of-phase sound spreads unnaturally. If out-of-phase sounds more natural, your wiring polarity might be reversed.
Audio Test Glossary
- Stereo
- A method of sound reproduction that creates an illusion of multi-directional audible perspective using two or more independent audio channels.
- Channel
- An audio signal path. In stereo audio, there are two channels: Left and Right, each assigned different sound components.
- Phase (In-Phase)
- The timing of sound wave waveforms. When the peaks and valleys of sound waves from the left and right speakers align perfectly, it is called "In-Phase".
- Out-of-Phase
- A state where the left and right speaker waveforms are inverted (180 degrees out of phase). The sounds cancel each other out in the air, creating an unnatural sensation where the center sound is missing. This happens when speaker + and - wires are connected in reverse.
- Panning
- The distribution of a sound signal into a new stereo or multi-channel sound field, positioning the sound image left, right, or center.
Frequently Asked Questions
- Q.Is this test tool safe? Is data sent to a server?
- Yes, it is completely safe. All test sounds are generated directly in your browser using the Web Audio API. No communication or data transmission with a server ever occurs.
- Q.Why does the "Out-of-Phase" sound strange?
- In out-of-phase playback, the waveforms of the left and right speakers are inverted. This causes the sounds to cancel each other out in the air, resulting in an unnatural sound with weak bass that feels like it wraps around your ears. This is the normal way out-of-phase audio sounds.
- Q.The out-of-phase sound feels more centered than the in-phase sound. Why?
- It is highly likely that your speakers or earphones are wired in reverse polarity (+ and - crossed). Please double-check the cable connections of your equipment.
- Q.Can I use this on my smartphone or Bluetooth earphones?
- Yes, it can be used to test any audio device, wired or wireless, as long as you are using a modern browser that supports the Web Audio API (such as iOS Safari or Chrome for Android).
- Q.What kind of sound is used for the test?
- The test uses dynamically generated "Pink Noise", which contains all frequency bands and makes phase differences and speaker characteristics easy for the human ear to distinguish.
Use Cases
New Speaker Setup Check
Use as a final check to ensure left/right channels and polarity (+/-) are connected correctly when wiring newly purchased amps or passive speakers.
Earphone/Headphone Wire Break Check
Useful for troubleshooting or checking for wire breaks when one side of your earphones produces no sound or sounds unnatural.
Audio Interface Routing Test
Diagnose if the routing settings between your PC and audio interface are correct, and if L/R panning is outputting accurately.
DIY Car Audio Wiring Test
When installing a car navigation system or car speakers yourself, use this to confirm the phase is not inverted (causing bass cancellation).
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