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How to check used headphones
Headphones are the one category here where the fault you care about is one you have to hear rather than measure, and where the part that always fails — the pads — is also the part that decides whether they sound like they should.
The short answer
Test channel balance and driver rattle with a sine sweep before you listen to any music. Music hides both. Thirty seconds of test tones will tell you more than an hour of your favourite album.
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Hear the faults that music covers up
- Play a slow sine sweep from 20Hz to 20kHz at moderate volume and listen for buzzing. A damaged driver rattles at specific frequencies, usually low ones, and music almost never holds a single tone long enough for you to notice. A sweep does. Any buzz or fluttering that tracks the tone is a torn or displaced diaphragm, and it does not recover.
- Check channel balance with a mono test tone. Play a centred mono signal and listen with both cups on, then lift each one in turn. The two sides should be the same loudness and the same tone. A quieter or thinner side means an ageing driver or a partial connection, and on many closed designs it cannot be fixed economically.
- Press each earcup gently against your head and listen for changes. A crackle, a cut-out, or a shift in level when you apply pressure points at the cable entry or the internal joint rather than the driver. That is a repairable fault on a detachable-cable model and a significant one on a fixed-cable model.
- Flex the cable along its whole length, especially at both ends. With audio playing, run the cable slowly through your fingers and bend it near each connector. Intermittent crackle at the plug or at the cup entry is the most common headphone fault there is. On a detachable cable it costs almost nothing; on a fixed one it is a soldering job.
- Inspect the pads and work out what a replacement set costs for this exact model. Protein leather perishes, flakes and goes hard over a few years, and worn pads change the seal, which changes the bass response. This is normal wear rather than a defect, but it is a cost, and on some models an expensive one.
- Examine the headband and the yoke where the arms swivel. Plastic headband forks are the standard structural failure point, and a hairline crack there becomes a break. Look inside the hinge, not just at the outside, and extend the band fully to its stops.
- On wireless models, check the battery honestly. Ask how long it holds from a full charge under real use, and compare that to the original rating. Lithium cells in headphones are frequently glued in place and not user-replaceable, which turns a worn battery into a fixed expiry date on the product.
- On noise-cancelling models, test the cancellation and listen for hiss. Switch it on in a quiet room. Failing ANC produces an audible noise floor, a pressure sensation that does not settle, or wind-like artefacts. Then check they still work passively with it off, because that is what you will be left with.
The one nobody checks
Channel balance. It develops gradually, the brain compensates for it within a minute or two of listening, and by the time you are enjoying a track you have stopped noticing. A mono test tone removes every bit of that adaptation and makes an imbalance obvious instantly. Do it first, before you have listened to anything you like.
Note
Pads are a consumable and should be treated like tyres — worn pads on otherwise excellent headphones are a normal, expected cost rather than a reason to reject them. What matters is whether a genuine set is still made for that model. A pair whose pads are no longer available has a definite end date, however good it sounds today.
What to measure
Higher is better▲Higher is betterLower is better▼Lower is betterMust be zero∅Must be zeroMust match the spec=Must match the spec
What to listen for, and what it means
| Metric | Which way | What it tells you | Healthy looks like |
|---|---|---|---|
| Driver rattle on a sweep | Must be zero | Physical damage to the diaphragm. | None, anywhere in the sweep. This is the one fault that does not get better. |
| Channel balance | Must match the spec | Whether both drivers have aged together. | Identical level and tone on a mono signal. |
| Cable crackle when flexed | Must be zero | The most common headphone fault. | Silent through the whole length, especially at the plug. |
| Pad condition | Must match the spec | A consumable that changes the sound as it wears. | Supple and sealing. Flaking or hardened pads are a known cost, not a fault. |
| Headband and yoke integrity | Must be zero | The standard structural failure point. | No hairline cracks inside the forks. Extend the band fully to check. |
| Wireless runtime vs rating | Higher is better | Remaining life in a cell that is often glued in. | Close to the original figure. Far short is an expiry date. |
| ANC noise floor | Lower is better | Whether the cancellation circuit is healthy. | Quiet. Audible hiss or unsettled pressure means it is failing. |
| Parts availability | Higher is better | Whether normal wear is repairable at all. | Pads and cable sold separately. Models without them are disposable. |
Walk away if
Walk away if
- Any buzz or rattle during a sine sweep.
- One side quieter or thinner than the other.
- Crackle when the cable is flexed near either end.
- A hairline crack inside the headband fork.
- Glued-in battery with visibly reduced runtime.
- ANC that hisses or produces unsettled pressure.
- A model with no replacement pads available.
What each fault is worth
Bring the measurement, not the opinion. Name the fault, name the fix, name what the fix costs — that is a solvable problem with two acceptable answers, which is what makes it work.
| What you found | What it actually costs | What to ask for |
|---|---|---|
| Worn or flaking pads | Changed seal and changed bass. | The cost of a genuine replacement set for that model. |
| Fixed cable with intermittent crackle | A soldering repair. | A large discount, or walk if you cannot solder. |
| Driver rattle | Permanent damage. | Walk away. This is not a negotiation. |
| Reduced wireless runtime | A product with an expiry date. | Price as a wired pair if they work wired at all. |
| No replacement parts available | Normal wear becomes terminal. | Price as disposable, not as an investment. |
Ready to go looking?
Take the checklist with you, then browse what is listed. Everything on this page works just as well the other way round when you are the one selling.
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