The issue of headphone "break-in" may seem obscure to many, but few headphone issues seem to win such attention. Bruised feelings and general frustration follow most any discussion, and polite discussions sometimes devolve into insults.
It's a complicated issue. This document has been drafted so that you can get all the arguments, pro and con. It's doubtful you'll find a more concentrated source of information on the subject anywhere else.
1. BURN-IN VS. BREAK-IN
2. THE ARGUMENTS
3. POINT/COUNTERPOINT
4. THE LATEST RESEARCH
5. WHAT DOES IT ALL MEAN?
1. BURN-IN VS. BREAK-IN
First, a bit of housekeeping. The terms "burn-in" and "break-in" are often used interchangeably, and most understand them to mean generally the same thing. A few skirmishes have been fought as a result of misunderstanding basic definitions, so maybe this is a good opportunity to avoid potential emotional bloodshed.
"Burn-in" is an electronic process wherein components like displays are kept on for long periods to detect potential flaws. On the other hand, "break-in" is a mechanical process requiring movement, much like breaking in a pair of shoes. This isn't to say that burn-in doesn't happen with headphones; rather, break-in is likely a less controversial factor. Break-in rarely means a radical change in sound profile; usually, it's more subtle, the main changes occurring in less than a day.
The most widely accepted theory?
- The main theory expostulates that, with use, the diaphragms of dynamic headphones become more flexible and vibrate more freely. It's analogous to the aforementioned example of breaking in a pair of shoes. The headphones achieve their tone with gradually fewer sonic faults, drawing closer to the designer's intentions. Meier Audio has different words for the same process: break-in "improves the mechanical properties of the suspension of the drivers and also tightens" the windings of the coil. With some headphones the difference is "day and night."
- A second theory has to do with a headphone's soft foam gradually conforming to the shape of one's head. Since the foam should already conform to the dimensions of your head from its very first use, this theory seems a stretch (so to speak). Aside from which, a head-speaker like the AKG K1000 - famous for its break-in - doesn't have any foam.
Some exceptions: The fixed-armature drivers in higher-end in-ear monitors operate differently than in dynamic headphones. As a result, you shouldn't notice break-in. You will, however, become increasingly expert at inserting the earpieces (or irritating your middle ear), which can affect the tone enormously.
I'm unaware of any research dealing with the break-in of electrostatic or orthdynamic headphones.
In many cases, break-in differences will not be as vast as some users claim. But break-in is important to consider if you're initially displeased with a phone. Give your headphones some time before making a final judgment.
2. THE ARGUMENTS
Opponents of this theory (and headphone break-in in general) urge skepticism. Among their most compelling arguments:
There's no "hard proof" for headphone break-in. In fact, nearly all the evidence is anecdotal. Surprisingly, not one modestly sophisticated experiment has been performed comparing pre- and post- burn-in headphones. While some technical articles have been written, they fall on both sides of the fence.
"Break-in" is actually placebo. "Placebo" is strictly a medical term referring to a specific body of research; it has no relevance to a discussion of headphones. "Expectation," however, may be a more reasonable psychological explanation. Accommodation - getting used to a headphone's sound - is another possibility. Both expectation and accommodation are commonly observed with headphone use.
Perceptual set and headphones. The well-supported (but less mentioned) concept perceptual set is may be the most sophisticated "psychological" explanation for break-in. Over time, the human mind simplifies complex perceptions into a kind of mental shorthand; it's a way our mind makes perception faster and easier. In stereophile terms, you can see it as a mental "pre-set."
Break-in suggests unstable components. The very concept of break-in suggests that headphone sound may be troublingly unstable. Wouldn't this suggest a significant product control issue?
Why is break-in always positive? With the wide variety of headphones (and ears), why do so many headphone listeners concur that the break-in change was positive? Logic seems to suggest that a number or listeners would find that certain phones would no longer be their taste - especially with fickle audiophiles.
Insufficient transducer mass. One involved theory posits that headphone manufacture is essentially different from that of loudspeaker transducers, making the detection of break-in changes "unlikely." Break-in changes can be detected in larger speakers, however.
Long-term auditory memory loss. Long-term auditory memory is generally thought to be the least of all the senses. It only stands to reason that suspected break-in effects should be relatively faint - or at least insufficient to rely on as hours turn to day, or even weeks.
Headphone pads fit better over time, making for a different sound. In a case where new and used K701s were suggested to have show sound differences, customer service suggested that, over time, improved fit may be a better solution than an unproven factor like "break-in."
3. POINT/COUNTERPOINT
Hard proof. It should be mentioned that, while proponents of break-in bear the burden of proof for their claims, opponents are equally without proof for their theories and counter-claims. And simply saying "we need more evidence" can be used by some to stonewall. It's not a compelling intellectual position.
Placebo, accommodation, and expectation. First, as noted, research on placebo cannot be generalized to a discussion of headphones. Moreover, accommodation and expectation are short-term psychological effects, and both are easily overridden by conscious reevaluation by the listener. For example, you can get used to the sound of a pair of slightly deficient earphones, but it's always possible to pause and recognize that the sound isn't very good. Break-in, on the other hand, seems to be more permanent.
Perceptual set is clearly involved in letting the human mind easily ignore some things while concentrating on others. But the mind's "preset" can be changed at will; break-in effects (with some unusual exceptions) become extremely stable.
Instability. No question, break-in seems to imply an instability that shouldn't be there - a potentially damning issue. On the other hand, shouldn't you expect the vibrating diaphragms in certain headphones to show at least some small sonic change over time, particularly just after initial use? It happens with other electronic components. More to the point, you'd expect audio engineers to prototype and test their headphones before release, and factor these effects into the design.
But tastes aren't uniform. A few listeners have complained that they prefer the pre-breakin
sound of their headphones.
Memory effects and headphones Visual memory is generally thought to be the strongest of the human senses. Auditory memory comes in a distant second, with the others rounding out the pack. However, when concentrating on specific details taken at a specific time, the reliability of visual memory can be expanded to almost the equal of visual memory. Aside from which, side-by-side break-in differences have been noted with the K701 and Denon D5000 phones, making memory unnecessary.
On the other hand, it's hard to explain sound changes in headphones observed by people who hadn't even been aware of break-in. It would be hard to say they were victims of "suggestion."
Used phonesIf break-in effects are simply "adjustment.", why don't people report break-in on their used headphones? So far, it hasn't happened - not once - in history. In addition, many users of new headphone don't didn't expect break-in. It just happened.
And there are a few other interesting issues:
Break-in, and headphone mass. It's interesting that there's little noticeable break-in with smaller headphones (like the iGrado or Sennheiser PX100 - but much more with larger phones (like the K701 and GS1000). In small phones, the metal "moving coil" in is less flexible; but larger phones offer more opportunity for movement and break-in. Break-in has actually been measured with full-sized speaker diaphragms. The larger the diaphragms, the more potential break-in. Also, there's no question that listeners with better headphones - and more sensitive systems - are better at differentiating sound.
Break-in of vintage headphones. A few owners of vintage phones - which had left in a closet and unused for years - were surprised at their inferior sound, noting annoying sonic flaws. However, after breaking them in again, the headphones regained their expected sound quality. Presumably, over time, the metal diaphragms tightened; over a few hours of break-in, the diaphragms regained their original flexibility, improving the sound.
Industry honesty. A cynic might suggest that vendors have everything to gain from customers getting used to their expensive headphones - equating break-in to a sales tool. But the very opposite might be the case. Manufacturers like Sennheiser say that their products sound great out of the box (which is true), but privately admit that they improve after break-in. Apparently, they're sensitive to the notion that their product might be less than 100% perfect on delivery.
Some find it curious that credible firms like Headroom, Headphone Solutions, and TTVJ concur in their support of headphone break-in - while unanimously rejecting that possibility for in-ear monitors (which have fixed armatures, which physically can't break in). Aside from having reputations for honesty, they're intimately knowledgeable about the products they vend. Then again, even a modest skeptic might conclude it's all an example of group-think with fewer facts than opinions.
Mixed messages. Ultrasone claims on on their website that their headphones require break-in, quoting between 4-16 hours, depending on the model. They also state that additional break-in will improve the sound even more. Grado has repeatedly supported the idea of break-in.
On the other hand, AKG and Sennheiser corporate headquarters in Europe seem to sending mixed messages. AKG's overseas corporate support sternly repeats (in standard, cut-and-paste feedback) that they "can neither confirm nor deny" the existence of headphone break-in." However, they counter that changes in sound may be the result of ear pad break-in. (Strangely, this is like substituting one kind of mechanical break-in for another.) Conversely, AKG U.S. support advises that their K701 headphones should get 300 hours of break-in. Sennheiser's official line is that premium headphones like the HD600 or HD650 sound great out of the box. Outside headquarters, however, they admit that several hours of break-in loosens the drivers and make the sound more fluid.
But in a way, it makes sense. One can understand why corporate support would be less than enthusiastic in admitting that their $300+ headphones weren't 100% perfect on arrival. Is a break-in of 300 hours - as reported with some AKGs - the kind of thing you want on your promotional material?
Proof, or the lack thereof. There's even a possibility that, say, break-in and perceptual set may be happening at the same time. Or that the right combination of ears, music, psychology, and hardware can show variability among listeners.
Sadly, most of the observational evidence supporting break-in is of a more general type: "I know it exists and don't need to prove it to anyone" or "The bass really opened up after 200 hours." Other reactions are more detailed and insistent.
Another option, which has been noted again and again, is that some of the differences many people presume is "break-in" relate to volume. When underpowered, good headphones may sound wan; but properly powered, treble and bass rise to their ideal level. Sometimes, finding that ideal level is what some mistake for "break-in."
Two studies are referenced in the Links section above, under "Hard evidence of break-in" and "Break-in validated."
Hard evidence of break-in. In one study, four new 10" speakers were broken in. Measurements indicated that the treble fell 20% after break-in - a uniform change of about 5hz.
Break-in validated. Two mid-range Audax speakers were measured over a comparable period of time. Specific readings showed differences between 18 and 64%.
Yet another study is extremely antagonistic to the idea of headphone break-in - but begrudgingly admits that break-in can probably be heard by some "golden eared" listeners. It is, then, not so much a better of whether break-in happens or not; the issue is the magnitude of the effect.
It all may come down to a simple equation: Skeptics have never heard break-in, and believers think they have.
There's a wide variety of headphones, cheap and expensive, made of different materials and conforming to varying tolerances, and attached to all sorts of amps and cables. Ears vary in their ability to discern sound. Expectation and belief may play their own roles. Even more confusing, small sound differences have been noted between batches of headphones. All of the above may be happening at the same time.
