Speaker and headphone test left, right, polarity and bass

How to test your speakers and headphones online

Test in this order: left and right first, then polarity, then bass, then a full sweep. Each step relies on the one before it. There is no point judging bass if one speaker is on the wrong side or wired backwards, because both faults change how the bass sounds.

The tool above has four parts. A recorded voice says "left", "right" or "both channels" from the matching side. A polarity test plays low-pass noise in phase and out of phase. A bass test offers a sweep from 20 to 200 Hz and single tones from 25 to 150 Hz. A full sweep runs from 20 to 20,000 Hz in 30 seconds.

Before you start, set the volume low, close other apps that play sound and sit where you normally listen. For speakers that means the usual chair, roughly the same distance from both. For headphones, check the L and R marks on the earcups and put them on the right way round, otherwise the test will report a fault that is really just how you are wearing them.

Left and right audio test: what the result means

A left and right audio test is passed when "left" comes only from the left, "right" only from the right, and "both channels" seems to come from the middle. Anything else points to a specific fault, and the voice makes it easy to tell which.

If the voice says "left" and you hear it on the right, the channels are swapped. If you hear "left" from both sides equally, the signal is being mixed to mono somewhere along the way. If one side is silent for both words, that speaker, earcup or cable is not getting a signal. If "both channels" sounds clearly off-centre, one side is louder than the other.

Left and right channels swapped or sound on one side: how to fix it

Swapped or missing channels are almost always a wiring or settings fault, not a broken speaker. Work from the simplest cause to the hardest and repeat the left and right test after each change.

• Headphones: check the L and R marks. Many people wear earbuds or headphones reversed without noticing until a stereo test.
• Speakers: follow each cable from the amplifier or computer. The output marked L should go to the speaker on your left as you face it.
• Settings: look for a balance slider and a mono audio switch in your computer's or phone's sound or accessibility settings. Mono audio is a real feature for people who hear better in one ear, and it makes every left and right test sound centred.
• Plugs: a 3.5 mm plug pushed in only part of the way often plays one side only or plays a thin, odd mix. Push it in fully and turn it slightly.
• Cables and adapters: swap in another cable. A cheap adapter or a damaged cable can drop a channel or turn stereo into mono.
• One side still silent with a known good cable: try the speaker or headphones on another device. If the fault follows them, the problem is in the speaker or earcup; if it stays with the device, it is in the output.

Once "left", "right" and "both channels" each come from the right place, move on to polarity. A pair can pass the left and right test perfectly and still be wired out of phase.

Speaker polarity test: in phase vs out of phase

A polarity test, often called a phase test, checks that both speakers push air in the same direction at the same moment. In phase, the low-pass noise should sound centred, solid and full. Out of phase, the same noise should sound diffuse, as if it came from nowhere in particular, with weaker bass. If your speakers sound fuller on the out-of-phase track than on the in-phase one, one speaker is wired backwards.

The reason is wave interference. When one speaker's wires are reversed, its cone moves out while the other moves in. At low frequencies the wavelength is several metres long compared with the gap between the speakers, so the two sounds largely cancel each other. The wavelength in air is the speed of sound divided by the frequency, with about 343 m/s at 20 °C: about 3.4 m at 100 Hz and about 17 m at 20 Hz. That is why reversed polarity hits the bass hardest and leaves the treble sounding fairly normal.

The test uses low-pass noise because noise covers a whole band at once and keeping it low puts it where cancellation is strongest. On headphones each ear has its own driver, so the out-of-phase track mostly sounds strangely placed; the test is most useful for a pair of speakers.

How to fix speakers that are out of phase

Reversed polarity is fixed by swapping the two wires on one speaker so that plus goes to plus and minus goes to minus at both ends. Turn the amplifier off before you touch the terminals.

• Look at the speaker terminals: plus is usually red, minus black. The amplifier outputs are marked the same way.
• Look at the cable: one of the two conductors is usually marked, by a stripe, ridges on the insulation, printed text or a different colour of metal. Use the marked conductor for plus on both ends of every cable.
• Check both speakers, not only the one you suspect. If both are reversed, they are in phase with each other and the test will pass; the fault you hear is elsewhere.
• Swap the wires on one speaker only, turn the amplifier back on at low volume and run the in-phase and out-of-phase tests again.
• If the in-phase track now sounds centred and full and the out-of-phase track sounds hollow, the pair is fixed.

With a subwoofer the same idea applies, but many subwoofers have a phase switch or control instead. Play the bass tones from your listening seat and set the control to whichever position gives fuller bass around the crossover frequency.

Bass test: how low can your speakers go?

A bass test shows the lowest tone your speakers or headphones can actually play. Start the 20–200 Hz sweep at a low volume and note the point where you first hear a clear tone; below that the speaker produces little or nothing. Then play the single tones from 25 to 150 Hz one by one to confirm the point and to listen for rattles.

Expect the bottom of the sweep to sound weaker than the top even on good equipment. The ear is less sensitive to deep tones: the international equal-loudness standard, ISO 226:2023, shows that very low and very high tones need far more sound pressure to sound as loud as mid tones. A speaker that plays 30 Hz at the same level as 100 Hz will still make 30 Hz seem quieter.

Around 20 Hz you reach the lower edge of human hearing. Sound below about 20 Hz is called infrasound, and at higher intensities very low tones are partly felt as vibration in the body rather than heard as a clear pitch. If the lowest tones feel more like a pressure or a hum than a note, that is normal.

The room also shapes bass strongly. Because bass wavelengths are metres long, the sound reflects off walls and floor and adds up in some spots and cancels in others. If one tone booms and the next one nearly vanishes, move your head or your chair half a metre and listen again before blaming the speaker.

Why phone and laptop speakers have no deep bass

Small speakers cannot move enough air at low frequencies, so a phone or laptop plays deep bass weakly or not at all. Bass needs large movements of air: a 50 Hz wave is about 7 m long, and a speaker a few millimetres across with almost no enclosure behind it cannot push the air hard enough to make it loud. Researchers working on microspeakers write that size restrictions pose increasing challenges to acoustic performance.

Many small speakers also lose the very top of the treble. The audio itself is not the limit: digital sound at 44.1 kHz can carry tones up to 22.05 kHz, and at 48 kHz up to 24 kHz. So if a bass tone or a very high tone is silent on your phone, that says nothing about your hearing or about the audio file. Try the same tone on headphones or on a proper speaker before you draw any conclusion.

Subwoofer test and the 80 Hz crossover

A subwoofer test checks that the subwoofer plays, that it joins the main speakers without a gap or a hump, and that nothing in the room rattles. The crossover is the frequency where bass is handed from the main speakers to the subwoofer. THX requires an 80 Hz crossover point in the setup menu of every THX Certified AV receiver, and 80 Hz is a common starting point for home cinema. It is not the ideal setting for every system; speakers that go deeper on their own may sound better with a lower one, and small satellites may need a higher one.

Play the single tones from 25 to 150 Hz in order from your seat. With a good setup they should seem roughly even in level, keeping in mind that the lowest ones will sound a little quieter to the ear. A clear dip near the crossover often means the subwoofer is out of phase with the main speakers; try its phase control. A big boom on one tone usually comes from the room or from the subwoofer's position, so try moving it along the wall.

Then run the 20–200 Hz sweep at a moderate volume and listen for buzzing from shelves, windows, picture frames and the subwoofer cabinet itself. A rattle that appears at the same frequency every time is mechanical. Find it by touching likely objects while the tone plays; the buzz stops when you hold the right one.

Frequency sweep test: rattles, buzzing and dead spots

A full frequency sweep, from 20 Hz to 20,000 Hz, runs through every pitch a speaker should play and shows where it rattles, buzzes, drops out or stops producing sound. Listen for a smooth tone that rises steadily. A sudden buzz, a crackle, a sharp drop in level or a gap where the tone almost disappears is worth a second listen.

Run the sweep once for each speaker by itself if you can, using the balance setting or by unplugging the other one. A fault in one speaker is much easier to hear without the second one covering it. Compare the two: a pair of identical speakers should sound nearly the same at every point of the sweep.

The top of the sweep has a second limit: your ears. The textbook range of human hearing is 20 Hz to 20,000 Hz, but it varies between people and narrows with age. In a study of 162 adults with normal standard hearing tests, everyone under 30 heard 16 kHz and about half heard 20 kHz; no one aged 51 to 60 heard 20 kHz, and no one aged 61 to 70 heard 18 kHz. If the sweep goes silent before it ends, the reason may be your speaker, your headphones or simply your age, and that last one is normal. The hearing frequency test on this site looks at this in detail; the tone generator lets you play any single frequency you want to check.

Headphone test: what to check on headphones and earbuds

A headphone test is mostly the left and right test plus the bass test. Make sure "left" plays only in the left earcup, "right" only in the right, and "both channels" sits in the middle of your head. If the centre drifts to one side, check the balance setting first, then the fit: an earbud that does not seal in the ear loses bass and level on that side.

Headphones usually reach deeper bass than any phone or laptop speaker, so the bass sweep is a good way to judge fit as well as quality. Seat each earbud or earcup properly and the low tones should become clearly stronger. If they do not, try another ear tip size or adjust the headband.

How loud should a speaker or headphone test be?

Quiet enough to talk over. Every test on this page works at a low or moderate level, and starting quietly protects both your hearing and your speakers. The WHO recommends keeping device volume at no more than 60 % of maximum, and its safe-listening standard with the ITU sets 80 dB for 40 hours a week for adults and 75 dB for children. At 90 dB the safe time drops to 4 hours a week.

Be careful with the lowest and highest tones. Because the ear is less sensitive at both ends, it is tempting to turn the volume up until a 25 Hz tone or the top of the sweep sounds loud, and by then far more energy is reaching your ears and the speaker than you feel. If you cannot hear a very high tone, do not turn it up to maximum: children and pets nearby may hear it clearly.

Speakers need the same care. Small speakers and tweeters are not built for long, loud, pure tones, so a continuous loud tone can overheat or damage them. Keep each test short, start quiet, raise the volume slowly and stop at once if you hear distortion.