Stable center
The center tone should feel locked between the channels, not smeared or pulled sideways.
Imaging and polarity
Stereo Test
Start with Left, Center, Right, and Movement. The clearly labelled advanced section then lets you compare mono, stereo separation, and channel polarity.
Browser audio engine
Ready — choose a test
Interactive channel map
Tap the ear you want to hear
Local audio
Drag sound position
Position and movement
Advanced comparisons
These sounds are intentionally different. Use them to compare signal structure and polarity—not channel loudness.
Web Audio is unavailable in this browser. Try a current version of Chrome, Edge, Firefox, or Safari.
Listen for continuity
What a healthy stereo image sounds like
Even movement
The sweep should cross every position smoothly with no sudden dip around the middle.
Matched edges
Far left and far right should feel similarly loud and equally distant.
Advanced polarity check
Focused center vs diffuse phase
The Focused Center control uses matching channel polarity. Diffuse Phase reverses the right channel, making the image spread out and reducing bass when the channels mix acoustically or electronically.
IN PHASE
Solid and centered
Both channels move together. Centered content usually feels focused.
OUT OF PHASE
Thin and diffuse
The right channel is inverted. The center weakens, especially on speakers.
Compatibility
Mono vs stereo—and why compatibility matters
The Mono button sends the same tone to both channels; Stereo sends different tones left and right so independence is unmistakable. When stereo is later combined to mono, opposite-polarity information can cancel. That is why phase problems may sound wide on headphones but lose vocals or bass on a single speaker.
Need a simple channel confirmation first? Use the left right audio test. For physical speaker layouts, open the surround sound test.
Useful answers
Frequently asked questions
What should a stereo movement test sound like?
The tone should travel smoothly from left to center to right and back without jumping, disappearing, or becoming much louder on one side.
Why is the center not in the middle?
Check system balance, headphone fit, earbud seal, and speaker placement. On speakers, sit equally distant from both. Hearing differences can also shift the perceived center.
What is audio phase?
Phase describes timing and polarity relationships between signals. When one stereo side is polarity-inverted, centered content often becomes thin, diffuse, or outside the head because the channels partly cancel when combined.
What is the difference between pan and balance?
Panning places a source across a stereo field by changing the channel signals. Balance changes the overall level of the left and right output channels.
Can laptop speakers create a stereo image?
Yes, but their close spacing limits width. Sit centered and close enough to hear separation without blocking either speaker.