Burn in. What does it actually do? And other various questions.

Have you checked MRael's AT page? This may answer some of your questions.

http://www.home.earthlink.net/~runni.../homepage.html

Hmm. Burn in is a little controversial. It might not exist. Of course, any physical system has some degree of instability and is subject to changes of varying magnitude and predictability. Still, the brain's perceptive systems are so adaptable that they may account for all the experiences that are called "burn in."

There was a famous psychological experiment where subjects wore inverting lenses 24/7. (They were mounted in a cast over the top of their heads so that cheating was ruled out.) At first, of course, the subjects stumbled about and had great difficulty doing even the simplest things. After a week or so, they became rather skilled at orienting themselves among the upside down visuals. After about a month, they saw everything right-side up. Their brains had made the adjustment complete. Moreover, when the lenses were removed, the poor subjects saw everything upside down again and had to make the adjustment once more in the other direction.

If our brains can do this much, you have to question whether any burn in effects could be detected even if they do exist.

*cringes*

Now I'm in for it.

Yes, zelkova is an elm variety native to Japan where it is well known from folklore and an important subject in art. It is particularly treasured for treatment as bonsai. My guess is that the awareness of this cultural fascination with that source of wood had more to do with its selection for headphones than any sonic properties.

I'm one of the people who feels that not only does speaker burn-in exist, but it is inherently logical. I'm quite a bit more suspicious of cable and electronics burn-in, though.

In terms of loudspeakers and headphones, you're talking about materials (the drivers) that empirically change their behavior after significant use -- it's actually measurable (I remember years ago reading an article where the physical driver behavior of loudspeakers were measured brand new vs. after substantial burn-in). The surrounds and flexures simply loosen up over time.

My experience with DIY amps has been that I don't ever notice any burn-in, so if it exists then it is undetectable by me at least. Also I recently built 2 pairs of the exact same DIY interconnect, the X-3 cable from www.tnt-audio.com. One I left burning in at work for a week non-stop, the other just sat on my dresser. Later I was able to compare both of them to each other and to my Straightwire Chorus. I could easily tell both of the DIY ones apart from my Straightwire Chorus, but I could not tell them apart from each other. The 100+ hours of burn-in had no discernable effect. I have no idea if headphones burn-in or not. My recently purchased brand-new HD580 sound nearly identical to my year old HD600. Close enough that burn-in is the the last thing I would worry about.

I have noticed that my mood and physical state (tired, sleepy, sick) does affect the sound. Much more so than I've ever noticed with burn-in.

Just to add another perspective to the conversation.. Burn in makes good sense from a mechanical perspective. If anyone here knows anything about high performance engines, you already know all about burn in (or 'break-in' as its usually called for engines, but the same thing). In an engine, the parts are under constant motion and stress. They are built to very specific requirements, but nothing will change the fact that manufacturing procedures are never going to be perfect. There will ALWAYS be small differences between each part.

For the first 600 miles or so of an engine, you are working with parts that are all different from each other. The piston rings don't match the cylinder, the crankshaft rods don't match the bearings. Nothing matches. But as you run the engine, heating it up, letting it cool down, going fast, going slow, the parts wear into each other. The rings expand and get worn down, until they exactly match the cylinder. The bearings expand and wear, until they exactly match the shaft rods. This process continues for a long time! 600 miles or so to reach 'normal performance' but they will keep getting better for the next 20,000 or more miles!

Headphones are the same. Lots of little moving things. coils, diaphrams, etc. None of them match, but with time, the parts will 'wear into' each other, and mold to one another. A wonderful thing.

Though there is something to be said for they psychology of it. Simply 'getting used' to it, causing your brain to adjust to match the new sound.

Perhaps its both, breaking in the phones, and yourself

peace,
phidauex

Well, the analogy with engines is perhaps a little misleading. In headphones, the parts mostly move in suspensions so that they don't touch each other. There isn't any friction to make them match each other better than the original manufacturing process was able to arrange. And where friction finishes the shaping of the parts in a system where exactly conforming shapes will contribute to the performance of the whole, break in is clearly an important beneficial contribution.

Definitely, headphones will have some kind of analogous changes with use (and even with age but without any use). However, in headphones, with no friction to speak of, with no changes in shape or mass in the parts, we are probably talking mostly about changes in the flexibility of the moving parts. You might expect them to become more flexible (flabby, if you don't like the idea) over time and with use. But, who knows, maybe some of them become more brittle.

So, phidauex, you do a good job of showing why engine break in is beneficial, but I still don't see an analogous reason for the undoubted changes in headphones to be beneficial. (With tubes, some burning in until they get to a relatively stable state would be just as beneficial in its way, and therefore more analogous with engine break in.)

Anyhow, with most of the reports of headphone burn in citing benefits, it makes me suspect that the bulk of the effect is at bottom accomodation of perception to a new experience.

*seeks cover under his desk*

As far as I know, most speaker driver will be tested with obvious change in statistics, such as resonant frequence, system damping, after a period of time of burning, let us say 100hours, after that, most of these statistics will come to be almost stable for a very long time, say 10 years. So that most manufacturers when designing their systems may have reference to those statistics with most duration, that is those after the first 100 hours, in order to make their products work in the optimized condition as long as possible. While for mass production, if they burn every of their products for such a long time, the cost may huge, so we need to burn it first to make it work in the designed condition. Of course, the obviousness of the improvement is decided by the nature of the materials.

I.M.O. same things might happen in the electric components,especially for those tubes but the change is some time too few to be detectable.

True, but it is precisely those "suspensions" (the surround on a loudspeaker, the flexure on a headphone) that change their physical behavior over time.

Because the materials from which surrounds and flexures are made behave differently after extended use than they do right out of production. With loudspeakers, the difference is often dramatic. I remember a dealer showing me this once years ago: he had demo models of an old model line that had been on the floor for months, as well as some of the same model brand new in a box. Both were approximately the same age. He unpacked one of the new one and had me physically move the woofers with my fingers. The difference in flexibility was apparent even using such imprecise measurement tools as my hands

Flexures are made by folds of material. They loosen up over time as they move. Again, as I stated above, I've actually seen this measured. So it's not just "perception."


Given that manufacturers of headphones are (we hope) aiming for the best long-term experience, and given that headphones do indeed sound different to some degree after "burn in," it follows that manufacturers would design their headphones so that they sound better after burn-in than before. So it seems entirely logical to me that most reports of burn-in cite benefits.

Tim,
all but one of the wooden AT headphones have been made from cherry wood from Japan's northernmost island of Hokkaido, the very first wood model ATH-W10VTG being the exception. Two wooden AT phones have been treated with a traditional dark red Japanese lacquer, the W11JPN and the W2002. There might be some kind of thin lacquer on my W100 as well, but it's not glossy or shiny, so I am not sure about it.

Break-in. It's real, it's dramatic, it's here to stay. This is was Ruach said in a post a couple of days ago: "I have just bought Matt's W100 and I did some basic comparisons between the 2 cans. Matt's W100 sounds a bit harsh with the bass response not as deep nor as tight as the one I have right now."

solomon said there had been a difference between a brand new and his older pair when he once compared them, and he feels his W100 still improves after more than six months of use.

JML has perceived obvious improvements during burn-in, and so have I - even after more than 300 hours - and so has Spad, with his W2002.

Wes,
You can run but you cannot hide. I admit that AT's claim of eternal improvement is hard to swallow, but after my experience with the W100, I'd have to say it's not only possible, it's likely. And I'd say Tim is right, it's probably the wood that plays a huge role in this. If the sound of a violin improves during centuries of use, why shouldn't a headphone's wooden enclosure become more flexible? Usually, a lot of burn-in effects are probably attributable to the drivers, MacDEF is absolutely right, but in the case of the ATs, the flexibility and the resonance behaviour of the wooden enclosures seem to be just as important.

Its pretty easy to understand that mechanically materials change with use (anyone here think that shoes don't break in?) but I've never bought the bit about the wood in the AT's being part of the break-in process. Not that it matters, of course. By the way, does an old violin sound different because of use or because of age?

i think that, while the properties of the wood of the enclosures may change slightly with use, it is much more likely age and humidity that will cause any notable acoustical changes. as the wood dries, it becomes more rigid and shrinks changing not only the stiffness of the enclosure but also the physical size. of course the opposite will happen as it absorbs moisture. it may be interesting to see if the woodies change seasonally as well as with break in.

other effects of break-in are most likely caused by fatigue in the drivers' materials. as the materials are flexed through more and more cycles, their mechanical properties change. this effect can easily be seen, to a much greater degree, when you continually bend a piece of wire. after awhile, it becomes brittle and finally breaks. the drivers are hopefully designed to avoid reaching this point of fatigue but that is basically what is happening.

MacDef,

Every point you make is quite reasonable. I had admitted that changes in flexibility of materials are extremely likely. It would be reasonable also that designers would take this into account so that the early performance would be less than the final, stable kind. In that case, however, I would expect to see in at least most owner's manuals some reference to that.

Does anyone own a pair of headphones where the manual says something like, "After considerable use the excellent sound of your purchase will improve. Please do not judge them by your first encounter?"

If there are no such warnings (and I have never encountered one), then I would doubt that the designers are taking the--admittedly reasonable--step of evaluating their products after long use. Or else their research has indicated that those changes are of such small magnitude and predictability that they are not worth taking into account.

*dashes out of harms way*

Wes,

i'm gonna offer my perspective on some of your (well thought out) points that macdef hasn't yet addressed:

the psycho acoustic effect of break/burn in really isn't given enough credit, but hey, it's stuff like this that makes me think the human brain is a lot more complicated than we can understand in this time and place.

i seem to recall a blurb in the sennheiser hd-580 literature that they should be given a few hours of break in (i don't feel like looking for it for a quote however). some speaker companies that include break-in sugestions in their manuals: psb, dynaudio, athena, and paradigm.

while i don't agree with your stance on break-in, i commend you on speaking your mind. i'm very comfortable with the possibility (and considering modern science, likeliness) that improvements i hear are imaginary.

*looking to see where Wes is hiding*

carlo.

Methinks the opposite, that the psychoacoustic effect of burn-in is given way too much credit. I don't listen to my equipment much during burn-in (except for occasional brief checks to see how it's doing). I eagerly await an explanation of how my perception of a device I am not listening to is subject to perceptual change. You have to listen to it to get used to it. If you don't, you don't. Yet I still hear changes over time.