Headphone burn-in: what changes, and what doesn't

What burn-in is supposed to do

New gear is said to sound tight, thin or harsh out of the box and to open up once it has played for long enough. The usual promises are looser bass, smoother treble and a wider soundstage, and the advice on how long to wait runs from a day of playing to several weeks.

That one claim holds two separate questions. Does the product change as it's used, and does your impression of it change? Both can happen. A measurement, or a blind comparison of the product against a record of how it sounded before, can tell them apart. Memory can't.

What happens inside a cone driver

A dynamic driver's cone hangs on a suspension: a flexible surround at its rim and, in a loudspeaker, a corrugated spider behind it. Those parts flex with every cycle of the music, and they get softer as they do. A softer suspension lowers the driver's resonance frequency, which changes the bass around that frequency.

Wolfgang Klippel's 2011 measurements of loudspeaker suspensions show the change in two stages. A fast break-in comes first: some manufacturers who track aging take their reference measurement after one hour of a power test, when most of the break-in is finished. A slow mechanical fatigue follows, and in some parts it keeps softening the suspension past 100 hours. The split differs from part to part. In one spider the paper tested, the break-in accounted for half of the total change and slow fatigue for the rest.

The paper models both stages by the mechanical work put through the suspension, so a driver played gently takes longer to get there than one on a power test. It measures loudspeaker parts. A headphone's dynamic driver has a surround too, but moves far less and takes far less power, and these measurements don't say how much of the effect carries over to it.

A headphone has one more part that changes with use. Ear pad foam compresses as it's worn, and because the pads set the seal and the distance between driver and ear, a compressed pad can change the bass and treble you hear.

Electronics, cables and planar drivers

Solid-state amplifiers and DACs have nothing to loosen. They do warm up, settling to their operating temperature over minutes each time they're switched on, and that happens every day whatever the hours on the clock. Vacuum tubes do change in early use: their operating current and gain drift over the first hours, which is why sellers who match tubes into pairs run them in first.

Cables have no known process that changes a conductor's resistance, capacitance or inductance through use at audio signal levels.

A planar magnetic driver has no surround or spider of the kind the suspension research measured. Its diaphragm is a thin film held under tension in a frame, and that research doesn't cover it.

How your hearing adjusts to new gear

The change in the listener is better documented. The ear adapts to what it has just heard. In a 2018 study by Piazza and colleagues, listeners heard one sound, such as an instrument or a voice, repeated five times, then judged a sound morphed halfway between it and a second one. The morph sounded more like the second sound, and the effect was there from the first trial.

That study ran over single sessions and doesn't measure weeks with a new headphone. It does show the direction of the effect: hearing a sound's character makes that character less noticeable in what follows. A headphone's tonal balance colors everything you play through it, so a treble lift that is obvious on day one can draw less attention later with the headphone unchanged. Driver changes and listener adaptation can happen at once, and a burn-in report on its own can't tell you which one you heard. The timbre page covers what that character is made of.

A burn-in schedule also has a practical cost. A few hundred hours at a few hours a day runs past many return windows, so judge a product while you can still send it back.

Testing burn-in on your own pair

You can't switch between a headphone and its younger self, so a before-and-after test needs a record of the before. Level matching matters most, because a slightly louder playback reads as fuller and more detailed.

1. Write down what you hear on three or four tracks you know well before the first long session: which instrument, which passage, too much or too little of what.
2. Use the headphone normally. Music at your usual level is fine.
3. Come back to the same tracks, from the same source, at the same volume setting, and compare against your notes.
4. Record a speaker instead of remembering it: a microphone on a stand, in a fixed spot, the same passage at the same volume before and after. Then compare the two files blind in the ABX test.
5. Compare two units of the same model blind, if you have them, one run in and one new, keeping in mind that some of any difference is unit-to-unit variation.

If a difference survives level matching and blind switching, it's real for your pair. If it doesn't, whatever changed is too small for you to hear.

Burn-in and the reviews on this site

Every review here follows at least two weeks of daily listening, typically four to eight weeks for flagship gear, before a score is committed, with level-matched comparisons and blind checks for small differences, as how we test sets out. So a verdict describes a product that has already had weeks of use, and none of our reviews credits a change in sound to burn-in.

The settling our reviews do describe is the listener's. The KBEAR KB02 review needed about a week of regular use before the fit stopped registering: after that, once inserted, the earphones "practically disappear". The review puts that week down to the ears adjusting.