[Prog Rock Man]

EDIT - I have a second theory on post 166, because of the following discussion (which can get very lively and has a lot of dross in it) and evidence found.
 
Here is why I think that the audiophile idea of headphone burn in, as in it is attributable to the headphone is nonsense and the actual reason as to why it appears to happen.

I have been collecting vintage headphones and overall I have 13 headphones, new and old. I tend to listen to one for a few days and then switch. I recently got a loan of so IEMs to try for the first time. I did not really take to them due to the lack of soundstage, comfort and lack of bass and treble. I was complementary about it sound, but thought that when I go back to my AKG K280 Parabolic full sized around ear four diver headphones, which I had been using prior to getting the IEMs, the K280s would sound spectacular. But they didn’t for a day or so.  Then they did. They returned to their spectacular sound.

Thinking back to various headphones and their supposed burn in, there are too many inconsistencies for there to be actual burn in. Some examples;

AKG K702. Supposedly  needs hundreds if not thousands of hours burn in. But they are very detailed and make little background noises easier to hear.  If you are not used to such detail then as you listen to music over the year, particularly albums you only listen to occasionally, you will keep noticing little details you have maybe not been able to hear before.  That is then attributed to the headphone, but it is not, it is you hearing something for the first time.

Sony DR4C. The 10,000 ohm headphone. Very difficult to drive and it took me a while to set the amp right for these to sound at their best. They are from the late 1970s and so are run in in as much as any minor mechanical changes to the driver have happened. But they got better as I got used to using them.

The AKG K280 Parabolic. As I said above I loved these from the start. I then tried IEMs which overall, I did not like as much. But when I went back to the K280s, because the change was so extreme, it took me a while to get used to them again. They have not changed, it was me.

Grado SR80s. They often sound a bit too bright at first, but quickly get to their dynamic attacking best. Moving on to something else afterwards can make that headphone sound dull.

AKG K44. Bought new my baby, cheapest cans, but remarkable in that I am always used to their sound and it has does not change one iota moving from one headphone to another or over a period of listening.

Sony DR5. They have always sounded bright and a bit thin. They were sold as hardly used, so may not have run in. But they sound unchanged in the time I have had them.

AKG K140. Vintage and going by marks they are well used. No change with them, but like the Sony DR4C they needed getting used to and sound a bit flat when I move to them from something more dynamic and bright.

All of the above changes are caused by me and my ears. The idea of burn in attributable to the headphones is not consistent and can be explained by changing from one headphone to another, or just getting used to each headphones sound; its dynamics, and particularly detail.

That is my reason why burn in does not happen as some audiophiles claim it does. All posts which say ‘that headphone needs burn in’ should actually read ‘that headphone needs getting used to’ or ‘that headphone does not suit your hearing, you can either try and get used to it, or get another pair.’

 

 

[Anaxilus]

Your psychoacoustic experience is not mutually exclusive to burn-in.  Burn-in doesn't negate psychoacoustics and psychoacoustics does not negate burn-in.  The fact you attribute the two to be the same means you lack an understanding of what burn-in is and why its done.  In fact, I had a recent experience where I believe burn-in made the phones sound worse than out of the box.  Read this:
 
 
Originally Posted by IpodHappy
 
As a physicist, I've spent a bit of time thinking about some of the factors which might impact audio performance of some of the IEMs. Here are my thoughts relating materials science with what might be happening. Please note that these hypotheses are not validated.
 
There are several changes which come from using your electronics:
1) With newer ceramic chip capacitors, there is some shifting of value under potential loading or aging due to instabilities in the dielectric materials. These capacitors are also not linear with voltage. I don't know what values are being used for current 2 or 3 driver cross overs or their body sizes, so I don't know if they are using the most recent dielectric materials. Older electrolytic capacitors with polymer dielectrics also changed during forming, a process through which the dipoles would align with the electric field potential.
2) With sufficient time, even at room temperature, Cu, eutectic and Pb-free solders (SbAgCu or SAC) will anneal, changing their electrical characteristics slightly. Plated Cu is especially susceptible (Cu traces on circuit boards). Vacancies are driven to the grain boundary surfaces, resulting is slight shifts of resistance, but no more than would occur due to standard strains (Cu foils are often used as strain gauges since the Cu resistance will shift under strain).
3) If enough current is passed through the electrical conductors, the electron wind bombarding the atoms will result in movement of the conductor atoms, again largely along grain boundaries, in an effect called electromigration. Hopefully, none of your electronics are designed so poorly as to experience this effect.
4) Epoxies rely on chemical bonding, called cross linking, during cure which results in densification and increased modulus (stiffening). During the manufacture of products using epoxies, there is often a push to reduce production time by reducing the time allocated for curing. This means there may be additional curing occurring in the field. How might this affect headphones? In a dynamic driver, the voice coil is often glued to the diaphragm with epoxy. As the epoxy continues to cure, the bond between the coil and diaphragm will strengthen, resulting in more energy transferred to the driver and less absorbed in viscoelastic deformation and internal friction. This would likely result in better high frequency energy transfer between the coil and driver, improving high frequency efficiency.
5) The molecular chains in rolled or cast plastic films (driver diaphragms) tend to align to the rolling direction or surface on which they are cast. This gives them a bit different modulus in plane compared to out of plane, and definitely impacts their coefficient of thermal expansion (CTE) in each of these orientations. Vibrations during speaker use create micro fatigue in these molecular chains, resulting in slight re-arrangement of the molecules. Usually, this results in a hardening of the material, caused work hardening. I would expect this to be a second order effect compared to the continued cross linking which might occur over extended time periods as mentioned in (5), but again would improve high frequency efficiency.
6) In designs with metal speaker diaphragms (some BA drivers), the metal will also experience work hardening with cyclical stresses. This would result in a slight hardening which would again tend to make the driver more efficient at reproducing high frequencies.
 
Just some thoughts.
 
Also search out dweavers measured tests on burn-in w/his Coppers.
 
Based on logic, science and my own long time experiences I absolutley believe in burn-in.  This debate is really pointless and boring.  Your phones are going to burn-in whether you like it or not just by use so whatever.  I also don't like to listen to phones or IEM's that require me to adjust my hearing to appreciate them.  There are many brands I don't like simply because I don't subscribe to that.  When I put on or take off my headphones I want as little discrepancy between what I hear from them and the real world as possible.
 
I'm finished w/ these silly discussions.

 

[kingtz]

Someone recently posted a FR curve of headphones before and after burn in, and there were minute, but clear differences. Unfortunately, the test was missing some controls and may or may not have been the most accurate. It'd be interesting to see if those changes are reproducible under more stringent and controlled experimental settings.
 
Also, the theory of the whole loosening of of the diaphragm after some usage makes sense to me. Unless, of course, headphones undergo factory burn in, then any more burn in thereafter will be moot.

 

[Roger Strummer]

The only measurements I've seen about burn in in headphones in particular was in Tyll's Headphone lab thread (here is the post). At least the initial measurements of burn in in the K701 seem to suggest, at least regarding frequency response, that the error of positioning of headphones is greater than the change of burn in if there is indeed one, which seems to say that big changes would be hard to encounter at least.
 
Also, due to that smallness, getting measurements doesn't seem to be as straightforward as one would hope, when Tyll returns that is probably one of the measurements that could be performed.

 

[Ypoknons]

If we could use a glass head for 300 hours, we wouldn't have to worry about positioning then would we? We could just keep them on the head all the time.

 

[Anaxilus]

If anyone actually does a more refined test I recommend using a NIB Ultrasone 2500 compared to a 3-500 hour one.  Biggest change I've heard in recent memory.  Of course that's in relative terms when I say 'Biggest'.  I say 2500 because its the only Titanium Ultrasone I have heard so far.  

 

[Prog Rock Man]

I accept that with speakers there can be some running in, but only to a very minor extent. The quoted !podHappy, which Anaxilus takes as proof, but is clearly a theory (hypothesis unvalidated) like mine shows no correlation between the described events happening and sound differences. At least my theory explains why we actually hear differences in sound.

 

[dexter3d]

I wonder, is there any headphone company which recommends 'burn-in'? If not, then consider if you are smarter than engineers who created your headphones..

 

[Prog Rock Man]

Some companies do offer 'burn in' services, such as Russ Andrews
 
http://www.russandrews.com/product.asp?lookup=1&region=UK&currency=GBP&pf_id=BURNIN&customer_id=PAA0281085510798ZLTBFKQLBZREKHZY
 
Only £15. Or you can send your cables to me and I will do it for £10........

 

[Anaxilus]

Quote:

I accept that with speakers there can be some running in, but only to a very minor extent. The quoted !podHappy, which Anaxilus takes as proof, but is clearly a theory (hypothesis unvalidated) like mine shows no correlation between the described events happening and sound differences. At least my theory explains why we actually hear differences in sound.

 
If that 'theory' doesn't explain how you can hear sound change you simply have little if any mechanical or scientific understanding.  You obviously completely ignored that your whole post is about psychoacoustics and not burn-in.  You thread is inaccurately labeled.  This is why I figured discussing the matter w/ you would prove pointless.  Enjoy your thread. 


 
Quote:

I wonder, is there any headphone company which recommends 'burn-in'? If not, then consider if you are smarter than engineers who created your headphones..

They do.  Good luck telling customers you are selling them preused headphones burned in for 100 hours.  Good luck telling the accountants and business managers that you can't sell these headphones right now because they need to sit on a lab bench for one week and burn-in rather than selling them at Best Buy right now.  Thinking the world is run by scientists and engineers is naive.  Some of you have no common sense.
 
Best wishes, enjoy the thread.

 

[Prog Rock Man]

 
Quote:

 
If that 'theory' doesn't explain how you can hear sound change you simply have little if any mechanical or scientific understanding.  You obviously completely ignored that your whole post is about psychoacoustics and not burn-in.  You thread is inaccurately labeled.  This is why I figured discussing the matter w/ you would prove pointless.  Enjoy your thread. 


 
 

I understand the mechanics, but there needs to be a proven link to sound changes. I know that my theory is all about psychoacoustics as that is my theory as to why we 'experience burn in'.
 
My view is that whilst there are some very minimal physical changes to a headphone, they do not properly explain why so many report burn in. Instead pyschoacoustics better explains burn in. Burn in that is attributed to the actual headphone is wrong.
 
We disagree, there is no need for you to get offensive about it.

 

[dexter3d]

Quote:

 

They do.  Good luck telling customers you are selling them preused headphones burned in for 100 hours.  Good luck telling the accountants and business managers that you can't sell these headphones right now because they need to sit on a lab bench for one week and burn-in rather than selling them at Best Buy right now.  Thinking the world is run by scientists and engineers is naive.  Some of you have no common sense.
 

If the sound really gets better, this would be an obvious choice for manufacturers, as headphone business is a lot about performance and about how they perform sonically against competition (with regard to e.g. cables, the story is quite different). Burn in doesn't cost much, it does not require any overseeing, and if headphones are constantly produced - there would be no 'lag' because of burn-in in production. And I agree - unfortunately, the world is not run by scientists - that's why we have so much BS here and everywhere
 
What I had in mind was a recommendation in a manual that your headphones will sound better after burn-in. This doesn't cost anything at all Does Sennheiser, AKG, Grado or any other manufacturer put such recommendation in their manuals? If not, why are they hiding such an important secret from you???? Or maybe they all are ignorant?

 

[Paganini Alfredo]

It sounds to me like what the OP is trying to say is that "burn in" is the same thing as "psychoacoustic" adjustment correct? Sounds like Anaxilus could use some common sense...

 

[yliu]

Quote:

6) In designs with metal speaker diaphragms (some BA drivers), the metal will also experience work hardening with cyclical stresses. This would result in a slight hardening which would again tend to make the driver more efficient at reproducing high frequencies.
 

 
Does that mean the Balanced armature IEM's will sound brighter after burn in??

 

[xnor]

I've posted a couple of measurements over the time, spread all over different threads, and all showed that the differences are smaller than those resulting from displacement, even if we're just talking about millimeters.
 
I've also seen pre and post burn-in impedance curves of headphones, and yes, of course the transducers change over time but not by much.
 
So I agree with Prog Rock Mans  theory.