Stereo Test

Introduction

The DeviceHub Stereo Test is a free browser diagnostic for verifying stereo imaging with left, right, and center tones synthesized locally through the Web Audio API. Where a basic speaker click only proves “sound exists,” this page asks whether your playback path preserves a usable stereo field, hard-left energy, hard-right energy, and a coherent phantom center, before you trust music, games, or video edits that depend on placement. Producers checking a new interface, remote editors validating headphones on a travel laptop, gamers confirming positional cues still pan, and support agents diagnosing “everything sounds stuck in the middle” tickets get a structured listening sequence without installing room-calibration suites. The test is honest about browser limits: it exercises two-channel stereo via StereoPanner-style routing, not proprietary spatial codecs. Pair it with Headphone Test for earcup isolation drills and with Surround Sound Test when you want a best-effort orientation pass that still cannot promise true 5.1 unless the browser exposes multichannel output. Mixing engineers on hotel laptops, podcasters aligning remote guests’ monitoring, and QA testers validating HTML5 game audio buses use structured left/right/center sequences to catch mono collapses that a playlist might mask with dense arrangements. DeviceHub’s stereo page is deliberately plain: fewer gimmicks, clearer imaging verdicts.

What this tool does

The tool plays dedicated left-only, right-only, and center imaging tones at a volume you control, with clear mode labels so you know which pan position is active. Optional alternating patterns help reveal intermittent channel dropouts that a single short tone might miss. Results and status text document the active mode for support notes. Playback starts only after user gestures to satisfy autoplay policies. Stopping disconnects oscillators immediately. The focus is perceptual stereo health, do sides separate, does center feel balanced, does the image collapse under mono modes, rather than absolute SPL calibration or frequency response charts. Center mode is included because many “stereo broken” tickets are actually missing phantom-center energy from a failed driver or extreme balance. Alternating patterns double as endurance checks for Bluetooth buffers. Labels stay visible so remote screen-share helpers can coach users without guessing which button was pressed.

When to use it

Run the Stereo Test after replacing a headset cable, after enabling or disabling accessibility mono audio, when a DAW mix sounds oddly centered on one machine but fine on another, before a competitive match that relies on stereo footsteps, and when comparing USB audio interfaces against onboard Realtek outputs. Use it on shared PCs where another user may have flipped balance or mono settings. Prefer Left Right Speaker Test when the primary question is which physical speaker cone fires; prefer this page when the question is whether stereo imaging as a whole still makes sense across left, right, and center positions. Reach for it when a DAW’s mono-compatibility switch might have been left on, when a soundbar’s voice mode sums channels, when comparing wired versus LDAC/AAC paths on the same headphones, and when onboarding new editors so everyone hears what “hard left” should mean on the studio cans. Skip surround marketing language here, use Surround Sound Test when you want that framing with explicit caveats. Broadcast engineers validating commentary booth cans before a live show also run a thirty-second stereo sequence so talent hears hard pans correctly before going on air. Game audio designers use it as a quick sanity check that the OS did not flip into a communications-only Bluetooth profile mid-session.

How it works

On each Start action, an AudioContext resumes and an OscillatorNode feeds a GainNode into a StereoPannerNode (or equivalent channel gain split) with pan values near −1, +1, or 0. Equal-power panning laws mean a center tone can sound slightly quieter per ear than a hard-panned tone at the same oscillator gain, that is expected psychoacoustics, not necessarily a broken driver. Alternate modes schedule pan automation so listeners can keep eyes off the UI while still catching dropouts. The browser outputs a stereo MediaStreamAudioDestination or default destination tied to the OS device; if the OS downmixes to mono, pan changes collapse and the test correctly reports that collapsed experience. No microphone permission is involved. DeviceHub does not stream sample libraries, tones are synthesized in real time for offline-friendly use after first paint. Equal-power panning keeps perceived loudness more stable across the arc than linear pan laws, which is why center can feel different from a naive 50/50 amplitude split. If ChannelMergerNode paths are used instead of StereoPanner on some implementations, the perceptual goal remains identical: isolate or blend L/R under user control. Sample-rate conversions in the OS rarely destroy imaging, but aggressive “3D” enhancers do. Offline-cached pages still synthesize tones without network audio fetches after first load.

Step-by-step instructions

1. Set headphones or a known stereo speaker pair as the system default output and sit in a quiet enough space to hear soft imaging differences without raising volume to unsafe levels.
2. Open the Stereo Test, keep on-page volume modest, and click Left so energy should appear strongly on the left channel while the right stays silent or near-silent on a healthy stereo path.
3. Click Right and confirm the mirror image, noting any bleed that suggests open-back leakage, mono downmix, or a damaged cable rather than intentional crossfeed.
4. Click Center and listen for a phantom image between both ears or speakers; if center is missing on one side, re-check balance and physical driver health before blaming the web page.
5. Optionally run an alternating left-right pattern for several seconds to catch intermittent cuts that only appear after thermal or Bluetooth packet issues begin.
6. Stop playback when finished, then optionally compare the same sequence on a second output device to build a relative baseline for tickets or gear evaluation notes.

Common problems

Mono collapse is the most common “failure” and often comes from OS accessibility settings, conference-room soundbars in dialogue mode, or single-driver laptops, not from DeviceHub. Bluetooth codecs and hands-free profiles can narrow imaging compared with wired playback. Virtual surround plugins may smear hard pans into diffuse fields; disable them for this check. If center feels wrong but sides are fine, inspect balance sliders and earcup seal. HDMI ARC devices sometimes force TV processing that alters stereo width, compare against a direct headphone path when diagnosing. Single-driver Bluetooth wearables marketed as stereo may still present a mono sink to the OS, imaging tests then correctly sound mono. Browser extensions that inject audio processors can alter pans; try a clean profile. Docking through DisplayPort audio to a monitor with one speaker collapses the field regardless of pan automation. If center vanishes only on speakers, check polarity inversion between left and right amps that cancels correlated content.

Privacy explanation

Stereo tones are synthesized locally in your browser tab. DeviceHub does not record listening behavior, upload audio, or require microphone access for this test. You start and stop every tone manually. Closing the page ends the AudioContext; no background playback continues after you leave. Imaging diagnostics never require capturing your room. DeviceHub does not store which pan modes you tried. Close the tab to ensure the AudioContext is discarded and no oscillator remains scheduled. Support staff can ask users to describe what they hear without collecting audio uploads, preserving privacy while still diagnosing mono collapse over chat. If you record your own screen for a ticket, mute or omit unrelated desktop audio. DeviceHub does not fingerprint your DAC or store EDID-like audio capability maps from this page.