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
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 often occurring in less than a day.
Given this, it doesn't make much sense to talk about headphone "burn-in" - since nothing is burned in during headphone use. Seen this way, it's not possible to "burn-in" a pair of shoes.
The most widely accepted theory?
- The main theory postulates 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. For some users, the difference is said to be like "day and night," though most regard it as subtle, indeed.
- 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, which can affect the tone enormously.
I'm unaware of any research dealing with the break-in of electrostatic or orthdynamic headphones.
In most cases, break-in differences aren't as vast as some users claim. But break-in is important to consider if you're initially displeased with a pair of phones. Why not give your headphones some extra previewing time before announcing 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 truly sophisticated experiment has been performed comparing pre- and post- burn-in headphones. In fact, even unsophisticated experiments are rare (though a few come close).
Significance of break-in. Some skeptics may admit that a certain amount of break-in will occur with a set of headphones. However, there's considerably less consensus when it comes to the significance of these changes, whether between brands or matched phones.
"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 have been commonly observed with headphone use.
Perception and memory. One of the most convincing arguments against headphone break-in can be found, not in sound, but rather visual research. Research into cognitive neuroscience indicates that the memory plays an important role in our final interpretation. This is analogous to how witnesses can have varied memories of an event, even though each person initially experienced the same thing.
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 theory posits that headphone manufacture is essentially different from that of loudspeaker transducers, making the detection of break-in changes "unlikely."
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 relatively short-term psychological effects, and both are easily overridden by conscious reevaluation by the listener. Break-in, for many, seems to involve more permanent sonic changes.
Instability. No question, break-in seems to imply an instability that shouldn't be there - a potentially damning issue. Then again, you'd expect audio engineers to prototype and test their headphones before release, and factor variables into the design. Could that be the reason why break-in always sounds good?
Significance of break-in. Both sides of this debate have been challenged when it comes to documenting the existence of break-in, much less the significance of this change.
The most widely accepted theory?
- The main theory postulates 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. For some users, the difference is said to be like "day and night," though most regard it as subtle, indeed.
- 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, which can affect the tone enormously.
I'm unaware of any research dealing with the break-in of electrostatic or orthdynamic headphones.
In most cases, break-in differences aren't as vast as some users claim. But break-in is important to consider if you're initially displeased with a pair of phones. Why not give your headphones some extra previewing time before announcing 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 truly sophisticated experiment has been performed comparing pre- and post- burn-in headphones. In fact, even unsophisticated experiments are rare (though a few come close).
Significance of break-in. Some skeptics may admit that a certain amount of break-in will occur with a set of headphones. However, there's considerably less consensus when it comes to the significance of these changes, whether between brands or matched phones.
"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 have been commonly observed with headphone use.
Perception and memory. One of the most convincing arguments against headphone break-in can be found, not in sound, but rather visual research. Research into cognitive neuroscience indicates that the memory plays an important role in our final interpretation. This is analogous to how witnesses can have varied memories of an event, even though each person initially experienced the same thing.
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 theory posits that headphone manufacture is essentially different from that of loudspeaker transducers, making the detection of break-in changes "unlikely."
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 relatively short-term psychological effects, and both are easily overridden by conscious reevaluation by the listener. Break-in, for many, seems to involve more permanent sonic changes.
Instability. No question, break-in seems to imply an instability that shouldn't be there - a potentially damning issue. Then again, you'd expect audio engineers to prototype and test their headphones before release, and factor variables into the design. Could that be the reason why break-in always sounds good?
Significance of break-in. Both sides of this debate have been challenged when it comes to documenting the existence of break-in, much less the significance of this change.
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.
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 largely 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, and 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? Conversely, would it be sensible for AKG to even acknowledge a "change" that is so controversial and unproven?
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 break-in 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 - but not convincing to many.
Another option, which has been noted again and again, is that "break-in" may be correlated to volume. Underpowered headphones can sound wan; but with properly powered phones, treble and bass rise to their ideal level. Sometimes, finding that ideal level is what some mistake for "break-in."
4. NEW RESEARCH
Hard evidence of break-in with speakers. 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. In another study, two mid-range Audax speakers were measured over a comparable period of time. Specific readings showed differences between 18 and 64%. It should be noted, however, that no such evidence has been published relating to headphones.
Yet another study is more antagonistic to the idea of headphone break-in - but begrudgingly admits that break-in can probably be heard by some "golden eared" listeners. (It's ironic that the skeptical researcher doesn't validate the existence of golden-eared listeners in the first place.) That said, even veteran headphone users admit the changes, if noted, are often relatively small.
Hard evidence of break-in with speakers. 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. In another study, two mid-range Audax speakers were measured over a comparable period of time. Specific readings showed differences between 18 and 64%. It should be noted, however, that no such evidence has been published relating to headphones.
Yet another study is more antagonistic to the idea of headphone break-in - but begrudgingly admits that break-in can probably be heard by some "golden eared" listeners. (It's ironic that the skeptical researcher doesn't validate the existence of golden-eared listeners in the first place.) That said, even veteran headphone users admit the changes, if noted, are often relatively small.
5. WHAT DOES IT ALL MEAN?
It all may come down to a simple equation: Skeptics have never heard break-in, and believers think they have. And perception may play a greater role in headphone break-in than some may admit.
It all may come down to a simple equation: Skeptics have never heard break-in, and believers think they have. And perception may play a greater role in headphone break-in than some may admit.
