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About this tool
Test speakers and headphones online: left/right channel check, stereo panning, 20 Hz to 20 kHz sweep, bass tones and phase test with a volume cap.
This speaker test generates every sound live with the Web Audio API instead of playing recorded files, so each test is exact and nothing is downloaded. Channel tests route chirps, pink noise or a 440 Hz tone through a stereo panner set fully left, centre or right; the panning sweep moves the sound smoothly between the speakers. The frequency sweep is a logarithmic sine glide from 20 Hz to 20 kHz (or a bass, mid or treble band) with the current frequency shown live. A tone generator holds any frequency for bass and rattle checks, and the phase test inverts the right channel to reveal reversed speaker wires. Output passes a limiter and is capped at −6 dBFS by default, or −12 dB in headphone mode.
Open Speaker Test on AltFTool — it loads instantly in your browser.
Set the Volume slider low (it starts at 50%, under a −6 dBFS cap), tick Headphone mode if you are wearing headphones, then raise your system volume gradually.
Under Left / right channel test pick Chirps, Pink noise or 440 Hz tone and press Left, Both or Right (or the ← ↓ → keys); Alternate L → R every 1.5 s switches sides for you.
In Frequency sweep choose a Range such as Full 20 Hz – 20 kHz and a 10, 20 or 30 s Duration, press Start sweep and watch the Now playing Hz readout; press K or Mark frequency where the tone appears or fades.
Use Tone generator & bass test presets (20–120 Hz) to check a subwoofer, then Phase test: In phase should sound centred and full, Out of phase hollow — if it is the other way round, a speaker is wired backwards.
Every tone, sweep and noise burst is synthesised in your browser, so frequencies are exact, there is no compression artefact, and the tests work offline once the page has loaded.
Output is capped at −6 dBFS (−12 dB in headphone mode), uses a squared volume curve and passes through a limiter. You must tick a box to allow full scale.
Live L/R output meters, a stereo position marker and a big frequency readout show exactly what is playing, so you can tell a speaker fault from a test you misheard.
Channel identification, panning, full-range and band sweeps, bass and treble presets, four waveforms and a polarity check, with keyboard shortcuts and your settings remembered.
| Speaker type | Usable low end | Bass presets to try |
|---|---|---|
| Phone or tablet speaker | 300–500 Hz | Mid presets only |
| Laptop speakers | 150–300 Hz | 120 Hz, 250 Hz |
| Earbuds and headphones | 20–40 Hz | 20, 30, 40 Hz |
| Bookshelf speakers | 45–70 Hz | 50, 60, 80 Hz |
| Floor-standing speakers | 30–45 Hz | 30, 40, 50 Hz |
| Subwoofer | 20–35 Hz | 20, 25, 30 Hz |
Figures are typical ranges, not specifications for any particular model. Room placement can raise or lower bass response considerably.
Press Left, then Right, under the channel test. Each plays only through that side using a stereo panner set fully to one channel. If the sound comes from the wrong speaker, the cables or the headphone orientation are swapped; if one side is silent, check the cable, balance setting and that speaker's power.
Human hearing spans roughly 20 Hz to 20 kHz. Small laptop and phone speakers usually start around 150–300 Hz, bookshelf speakers around 50–60 Hz, and a subwoofer can reach 20–30 Hz. Run the full sweep and mark where the tone becomes audible and where it fades to see your system's usable range.
Hearing above about 15–17 kHz declines naturally with age, so many adults cannot hear the top of the sweep even on good speakers. Some speakers and Bluetooth codecs also roll off high frequencies. Compare headphones and speakers: if both stop at the same point, the limit is probably your hearing.
Open the tone generator and play the 20 to 120 Hz presets, or run the Bass 20 – 200 Hz sweep. Listen for where the subwoofer takes over from the main speakers, and for buzzing panels or rattles. Keep the volume moderate: low tones carry a lot of energy for how loud they seem.
It plays the same signal through both speakers, first with matching polarity and then with the right channel inverted. In phase sounds focused and full; out of phase sounds diffuse with weak bass because the waves cancel. If the out-of-phase setting sounds better, one speaker's positive and negative wires are reversed.
At moderate levels, yes. This tool caps output at −6 dBFS, or −12 dB in headphone mode, and limits peaks, but your system volume still sets the final loudness. Start low, avoid long sustained high-frequency or sub-bass tones at high volume, and stop if a speaker distorts or rattles.
Check the balance slider in your operating system's sound settings first, then swap the speakers or earbuds to see whether the problem follows the device. Earwax, a damaged driver or a partially inserted 3.5 mm plug are common causes. A mono audio accessibility setting will make both sides sound identical.
Pink noise contains all audible frequencies with equal energy per octave, which sounds balanced to our ears rather than hissy like white noise. Because it covers the whole range at once, it makes channel identification, panning smoothness and phase differences easy to judge without a melody or a voice.
Yes, in any current mobile browser. Bluetooth adds latency, so the sound may lag the button by a fraction of a second, and some earbuds apply processing that colours the sweep. Turn off any spatial audio or mono mode on the device for an accurate left and right check.