Reading the results like a technician
Channel test: both sides should be equally loud at the same volume setting. A dead side is usually cabling or balance; a quiet side is usually balance, amp channel or speaker positioning.
Layout probe: we read maxChannelCount from your audio pipeline — the maximum number of channels exposed to this browser audio context. It is a capability ceiling, not proof of your physical speaker layout. Confirm the mapping by listening to every offered channel. If it says 2.0 while you own a 5.1 system, check your OS sound settings before testing again.
Bass drop (150 → 20 Hz):the frequency where output disappears is your system's practical low end. Two caveats: rooms create bass nulls at specific spots (move your head half a meter and 60 Hz can reappear), and at very low frequencies you may feel output before you hear it — both are normal physics, not defects.
One channel down: a decision tree
A missing or weak channel has maybe five common causes, and they sort cleanly by cost: software settings are free to fix, cables cost a few dollars, amplifier channels and drivers cost real money. Work top-down and rule out the cheap explanations first.
- Both sides silent? Not a speaker problem. The OS is almost certainly routing audio to a different output device — an idle HDMI monitor with built-in speakers is the classic culprit. Fix the output selection in your sound settings, then come back.
- Center the balance slider.Every operating system has a per-device left/right balance control buried in its sound settings — on Windows under the output device's properties, on macOS under Sound → Output. Audio utilities, remote-desktop sessions and driver updates are all known to nudge it, and a balance sitting at 70/30 is indistinguishable by ear from a failing amplifier channel. Confirm it reads dead center before diagnosing anything downstream.
- Reseat the connector. A half-seated 3.5mm plug has a recognizable signature: vocals nearly vanish while instruments continue, the sound turns thin and phasey, or only one channel plays at all. A stereo TRS plug carries left on the tip, right on the ring and ground on the sleeve; seated a few millimeters short, the contacts land on the wrong bands. When ground floats, the amplifier reproduces the difference between the left and right signals — and because lead vocals are usually mixed to the center of the stereo image, identical in both channels, they cancel almost completely. This is the “karaoke effect,” and it is diagnostic: no blown driver produces it. Push the plug in until it clicks fully home, then rerun the left and right checks above. If the symptoms survive a fully seated plug, try a different cable before blaming the speakers — jack contacts wear and oxidize, and a frayed cable produces the same partial-contact behavior.
- Run the swap test. At the amplifier, exchange the left and right speaker cables. If the fault moves with the cable, the speaker (or the cable itself) is the problem; if it stays on the same side, the amplifier channel or the source is. The same isolation logic works without a screwdriver: run the same checks over Bluetooth, then over the wired jack, then into a pair of headphones on the headphone bench. Whatever the fault follows is what needs replacing.
- Check polarity if the sound is hollow.Both channels playing, but the mix sounds thin, bass is weaker than it should be and the center image is diffuse — that pattern points at one speaker wired with plus and minus reversed. The two cones then move in opposition, and low frequencies, which are largely shared between channels, partially cancel in the air. Nothing is damaged; verify that the amplifier's red terminal goes to the speaker's red terminal onboth sides, and use the phase check on the headphone bench to confirm the fix.
The honest surround story
A downmixed surround test file cannot fail, which is why it proves nothing. When a website plays a “7.1 test MP3” or a YouTube “5.1 channel check,” the browser decodes the file and hands it to the operating system's audio pipeline. If that pipeline is configured as stereo — the default on almost every computer — the OS folds all six or eight channels down into two before anything reaches your hardware. You hear “rear left” announced from your front-left speaker and conclude the test passed; it tested nothing, because the same downmix plays identically on a pair of earbuds. That is why this page reads maxChannelCount— the number of discrete channels your browser's audio context can actually address — and shows you the honest figure, usually 2, instead of playing a file that succeeds by definition. If you want the number to change, change the pipeline, not the file.
A real 5.1 or 7.1 check needs discrete channels surviving the whole path. Concretely: the OS output must be configured as 5.1/7.1, and the physical link must carry that many channels. HDMI does — up to eight channels of uncompressed PCM. Optical (S/PDIF) does not: it carries only two channels of PCM, and surround over optical requires a Dolby Digital or DTS bitstream, which a browser does not emit. The receiver end matters too: set it to a direct or straight mode rather than an upmixer (Dolby Surround, DTS Neural:X), because an upmixer will happily invent rear-channel content from a stereo feed and make a broken pipeline sound “fixed.” With all of that in place, reload this page — the layout probe should report 6 or 8 — and press each per-channel button in turn. Our full method is documented on how we test.
Bass expectations by hardware class
Typical low-frequency limits by hardware class — expectations drawn from how these designs usually behave, not lab measurements of your unit: laptop speakers roll off steeply somewhere around 200–300 Hz, small powered desktop speakers hold on to roughly 100–150 Hz, bookshelf speakers with 4–5 inch woofers commonly reach 60–80 Hz, and a system with a working subwoofer should stay clearly audible down to 30–40 Hz. If the bass drop on this page goes silent far earlier than your class predicts, suspect configuration before hardware: a crossover set too high, an OS “enhancement” filtering the lows, or a subwoofer level knob at minimum. Two physics caveats apply — rooms create standing-wave nulls, so moving your head half a meter can bring 60 Hz back, and near the bottom of the sweep you may feel pressure before you hear tone. A laptop that quits at 250 Hz is behaving exactly as designed, not failing.
Note that our sweep starts at 150 Hz, which is already below a typical laptop's comfortable range — faint output from the very first second is expected there and tells you nothing is wrong. The sweep earns its keep on hardware that claims real low-end: it finds the frequency where the claim stops being true.
Distortion, buzz and rattle at volume
“It sounds bad when loud” resolves into three distinct mechanisms, and the sweep separates them because each lives in a different part of the spectrum:
- Port chuffing— a breathy “whoosh” riding on deep notes, strongest in a narrow band near the bass-reflex port's tuning (often somewhere in the 40–80 Hz region on bookshelf designs) and worse with the port close to a wall. It is turbulent air, not damage. Pull the speaker out from the wall or trim the bass EQ a few dB.
- Clipping — a harsh, gritty edge that lands on everything, both channels equally, and appears as the volume approaches maximum. That is the amplifier running out of clean output, and backing the level off is the whole fix. If the same grit appears at moderate volume on one side only, stop suspecting the amp and start suspecting that driver.
- Buzz or rattle on bass notes — narrow-band and mechanical: a loose grille, a badge, cone damage, or something on the desk resonating. Use the bass sweep above to find the offending frequency, hold it there, then hunt the rattle with a hand on the cabinet and the desk. A rattle that follows your hand pressure is hardware you can tighten; one inside the cabinet on a speaker that has been dropped may be a rubbing voice coil.
- Muffled after cleaning / rain / pool day — water in the grille. Power the device down, let it dry thoroughly, then re-test here.
- Hiss that changes with the volume knob— noisy source or a cable picking up interference; if the hiss is constant regardless of volume, it's the powered speaker's own amp floor, which is a specification, not a fault.
When to suspect the amp or DAC instead of the driver
Drivers and electronics fail differently, and one swap usually tells them apart. A driver fault is local: it stays with the same physical speaker when you exchange cables, and it is usually frequency-localized — a buzzy midrange, a dead tweeter, distortion that only the woofer's range triggers. An amplifier or DAC fault follows the source: the same imbalance or grit shows up on whatever speakers you connect, and it tends to affect the whole band at once. A few specific tells: a one-sided level drop that survives both a cable swap and a centered balance slider points at the amp channel; crackling when you turn the volume knob is a dirty potentiometer in the analog stage; pops and dropouts that appear on every output — speakers, headphones, Bluetooth — are the DAC or its connection, and no speaker purchase will fix them. When in doubt, feed the suspect amplifier a known-good source and the suspect speaker a known-good amplifier before spending money on either.
Testing a home-theater setup properly
The honest path: set the OS and receiver to your real layout as described above, reload this page, and use the per-channel buttons to confirm each physical speaker answers to its name — the front-left tone should come from front-left, not a rear. Wrong mapping means swapped wires at the receiver's terminals or a wrong speaker assignment in its setup menu, and the per-channel tones will tell you exactly which pair to trace. For calibration beyond channel identity — levels, distances, room EQ — your receiver's built-in microphone routine does what a browser legitimately cannot.