Burning in Headphones ? WTF ?

[janengelbrecht]

I am saying that "break in" or "burn in" if it is a real phenomenon is just the materials being degraded over time and this is not desirable. The audiophools think they are doing something magic, then it stops, and they have a static situation after that.

I am asserting that if there is a real effect it does not stop when they want it too. Once they have reached their "perfect" performance after break in, then they have a short time to enjoy their perfect sound and should start breaking in another set immediately so they have another pair ready to use and throw when the current pair "breaks in" beyond  their preferred sound.

Audiophools just feel all warm and fuzzy inside thinking that their magic wands and incantations have an effect on the real world that us mere mortals can't do.

 

[Lightages]

Of course I am open to any new evidence. Show me some repeatable performance measurements before, after, and long term after burn in and I will change my behavior to match observed and real evidence. Anything else is just superstition and personal bias.

[Yago]

Suppose could ask Adam if they have measured it?
Can only say fek-off!

[Mark Hennessy]

As with most hi-fi folklore, there is a grain of truth about it. I've certainly heard (and measured objectively) burn-in of bass drivers, caused by the "spider" (the rear suspension - usually yellow in colour), which changes during the first use. Here's what one manufacturer says:

Do I need to 'burn-in' my Harbeths?
No: the only component part of a Harbeth loudspeaker that can change as a result of the exercise known as 'burning-in' is the resin-doped cloth suspension that centres the neck of the cone in the magnetic field - sometimes called the 'spider'. Under the microscope, once the resin has been worked, it crazes into millions of small interconnected islands. This process is irreversible and takes only a few hours - or less, with bass heavy music played rather louder than normal. After that, the drive unit can be considered fully aged, and the resonant frequency has settled at its final value and will stay at that value.The ferrofluid used in Harbeth tweeters will become appropriately viscous after a few minutes operation. Neither the coils, resistors, capacitors, cables no any other part of a Harbeth speaker has any short-term ageing mechanism.

The bass drivers I've observed that have noticeable "burn-in" are made by Audax. As well as showing a change from brand new, they are also quite temperature sensitive. This might be at least partially caused by the rubber surround as well as (or instead of) the spider, but whatever the mechanism, it's easy to discover by measuring Fs. I have seen this elsewhere, but the Audax drivers I'm thinking of exhibited it more than usual.

It's not impossible to imagine that similar mechanisms might exist in headphone drivers. However, there's no need to specially "burn in" following a specific procedure - if there was, it would be done in the factory. Doing this or not will have no impact on the lifetime of the units - it's not like running in an engine back in the old days.

Away from this, "burn-in" = "getting used to".

[Mark Hennessy]

Of course I am open to any new evidence. Show me some repeatable performance measurements before, after, and long term after burn in and I will change my behavior to match observed and real evidence. Anything else is just superstition and personal bias.

My experiences with 6 samples of the Audax AP100Z0 are about a quarter of the way down this page: http://www.markhennessy.co.uk/audax/background.htm

As I said above, I think these drivers are worse than most in this regard, but I have seen similar behaviour in other woofers.

[AndyC_772]

Of course I am open to any new evidence. Show me some repeatable performance measurements before, after, and long term after burn in and I will change my behavior to match observed and real evidence. Anything else is just superstition and personal bias.

How is it "superstition" or "personal bias" to suggest that, just maybe, the shape of a stiffness vs time graph might be asymptotic to some long-term value around which a speaker is designed?

[hs3]

Some documented measurements with loudspeaker drivers and the change in parameters:

http://vikash.info/audio/xls10/

http://vikash.info/audio/audax/break-in.asp

[janengelbrecht]

Of course I am open to any new evidence. Show me some repeatable performance measurements before, after, and long term after burn in and I will change my behavior to match observed and real evidence. Anything else is just superstition and personal bias.

How is it "superstition" or "personal bias" to suggest that, just maybe, the shape of a stiffness vs time graph might be asymptotic to some long-term value around which a speaker is designed?

You then think that a process suddenly stops ? As i see it it must mean that the headphones will rapidly become bad then They will then have a short period of time where they sound good after some burn in...and then quickly turn bad

Well nothing points in this direction....im happy to say that i in 20 years....been the happy owner of at leat 25 pair of high end headphones used in my music recording studio...never have observed anything like this
But of course..my ears are not objective....so give us some hard evidence....scientific data...then i propably could become a believer too <

And we are talking small units now..not big 8-12" hifi speakers

[AndyC_772]

You then think that a process suddenly stops ? As i see it it must mean that the headphones will rapidly become bad then

http://dictionary.reference.com/browse/asymptotic?s=t

[janengelbrecht]

You then think that a process suddenly stops ? As i see it it must mean that the headphones will rapidly become bad then

http://dictionary.reference.com/browse/asymptotic?s=t

Well manufactures with great ressources has studied all there is to study about the physics of loudspeakers used in headphones and they all say: there is no such thing as a need for a burn in period
So i tend to say that until hard evidence is at the table it is just believes - religion if you want
I admit you can make a hypothesis about it - and make an asymtotic curve that states it - but where is the science behind to support it ?

[Mark Hennessy]

Some documented measurements with loudspeaker drivers and the change in parameters:

http://vikash.info/audio/audax/break-in.asp

Same drive units I measured. Done independently, but at about the same time. In fact, Vikash and I were just 2 of many people measuring the same thing with these very drive units - as a result of Maplin selling them off cheaply some 10 years back there was a lot of people building with them. I link to a diyaudio.com thread from my webpage that has a lot more background.

So, there is plenty of evidence that driver suspension compliance can change during the first few hours of operation (and it changes with temperature - measure it for yourself!). And I've quoted a manufacturer that explains what is happening with the spider from new. Plenty of other manufacturers say similar things. Unlike many popular audio beliefs, this particular one is unusually far from religion.

[Biff383]

  I would just as soon burn in my own. It helps to know what's bad so you can truly appreciate what is good. This is the reason that I buy my pencils unsharpend.

[janengelbrecht]

Excuse me....some measurements from a big HiFi unit is used as arguments in a discussion about SMALL headphone units ? And data is only from ONE manufacturer ? Thats not science in my book

[Yago]

The only way to settle this is to ask PhotonicInduction to burn some headphones in with that cap of his! 

[Lightages]

Those woofer aging results look interesting and do point to something changing more rapidly at the start and tapering off. Of course this is evidence for a woofer changing and reaching a point of "broken in". This could be for a number of factors, like excess glue at the edge of the spider or surround cracking, or the doping used in the spider cracking, or something similar. It could also be from the voice coil changing shape from abuse from the testing. Maybe there were environmental conditions that changed too. So it is possible that a woofer changes its characteristics to a more stable one during a break in period. If this could be repeated for other woofers with controlled environmental conditions it would be more evidence.

The problem I see with the tests referred to above is that the woofers were tested at their limits with a signal they don't normally deal with. They were tested at "approximately xmax" which could mean beyond their rated excursion limits too. At this point all the tests seem to indicate is that you can change a woofer's characteristics by abusing them. I am not surprised.

The construction of headphones and the materials used are different than those of the woofers tested. The results of the woofer test might translate to headphones but it is not a sure thing. I also think that the testing of headphones at the edge of their capacities is just as likely to cause unwanted damage instead of improving them.

The correct test to see if headphones actually do change in characteristics under normal and non-abusive use is to put them on a binaural mic head and play music through them at correct levels and measure their response each ten hours for 3 months, and under controlled environmental conditions. Do this with ten pairs of headphones, the same model or not, and I would have much more confidence in the results.

[Yago]

Found a bit more on loudspeakers:
http://www.gr-research.com/burnin.htm

[janengelbrecht]

Those woofer aging results look interesting and do point to something changing more rapidly at the start and tapering off. Of course this is evidence for a woofer changing and reaching a point of "broken in". This could be for a number of factors, like excess glue at the edge of the spider or surround cracking, or the doping used in the spider cracking, or something similar. It could also be from the voice coil changing shape from abuse from the testing. Maybe there were environmental conditions that changed too. So it is possible that a woofer changes its characteristics to a more stable one during a break in period. If this could be repeated for other woofers with controlled environmental conditions it would be more evidence.

The problem I see with the tests referred to above is that the woofers were tested at their limits with a signal they don't normally deal with. They were tested at "approximately xmax" which could mean beyond their rated excursion limits too. At this point all the tests seem to indicate is that you can change a woofer's characteristics by abusing them. I am not surprised.

The construction of headphones and the materials used are different than those of the woofers tested. The results of the woofer test might translate to headphones but it is not a sure thing. I also think that the testing of headphones at the edge of their capacities is just as likely to cause unwanted damage instead of improving them.

The correct test to see if headphones actually do change in characteristics under normal and non-abusive use is to put them on a binaural mic head and play music through them at correct levels and measure their response each ten hours for 3 months, and under controlled environmental conditions. Do this with ten pairs of headphones, the same model or not, and I would have much more confidence in the results.

again: 

[Mark Hennessy]

The problem I see with the tests referred to above is that the woofers were tested at their limits with a signal they don't normally deal with. They were tested at "approximately xmax" which could mean beyond their rated excursion limits too. At this point all the tests seem to indicate is that you can change a woofer's characteristics by abusing them. I am not surprised.

Incorrect.

Xmax is maximum linear excursion. Beyond that, the displacement becomes non-linear - it looks like "soft clipping" if you measure it with a microphone. It comes about as a result of voice coil length and gap length. Knowing Xmax is useful when determining how much power at a given frequency you can put into the system, given the box you've designed for it.

Xmax is nothing whatsoever to do with mechanical excursion limits. These are much larger than Xmax - typically twice.

Running them at Xmax at 15Hz for a while is not testing them at their limits. The low frequency is chosen to ensure that hardly any electrical power is required to achieve that displacement, so there was no question of thermally overloading the voice coil. In normal use, they can be expected to be regularly pushed past Xmax - especially such small bass units (4").

The tests outlined are completely normal practice in the loudspeaker industry.

And I quoted from a loudspeaker drive unit designer in my first post - where one mechanism was explained (spider resin). I know several loudspeaker drive unit designers BTW - I'm an engineer, not an "audiofool" - but the quote I provided was already in the public domain, so there is no problem referencing it.

There is plenty more evidence out there if you search for it - I'm not going to be made to feel guilty for only providing a limited amount of data as I assume everyone can use a search engine. All I wanted to say is that this effect is real - unlike a lot of stuff claimed by audiophiles. How audible it is depends on a lot of factors - I'm not about to get into that. And it's the "grain of truth" that I referred to in my opening post - I'm not claiming that headphone drivers are (or are not) affected in the same way - but you can see how the link could be made.

[janengelbrecht]

Now i understand the problem....people hear of it in hifi loudspeakers and automatically thinks it also is an issue in small headphone units I see .... well then i can still tell my "friend" his scheme is fraud (Not really a friend just somebody im forced to be around now and then )

[dannyf]

people hear of it in hifi loudspeakers and automatically thinks it also is an issue in small headphone units I see

You are fighting a war of your imagination.

No one said that, ***automatically***. What people said is that those units will change over time, so it is entirely within reason, and science, to think there is a rationale behind burn-in. Whether it will actually produce an audiable change, being it an improvement or deterioration, is unknown.

.... well then i can still tell my "friend" his scheme is fraud

You are within your right to say anything to anyone - that's what freedom is all about.

Just remember, don't make your science into a religion, or your religion into a science.

And be a better reader next time.

[SL4P]

2c worth.

a) if they need burning in - they probably aren't that well made wrt tolerances/alignment etc.

b) the only thing that will perhaps improve (change the audio performance), will be the 'adhesive' boundaries between rigid components and moving/flex parts.

Not what I'd call a scientific process unless the goal is to separate naive buyers fro their money.
Good luck to him.

[Lightages]

The problem I see with the tests referred to above is that the woofers were tested at their limits with a signal they don't normally deal with. They were tested at "approximately xmax" which could mean beyond their rated excursion limits too. At this point all the tests seem to indicate is that you can change a woofer's characteristics by abusing them. I am not surprised.

Incorrect.

Xmax is maximum linear excursion. Beyond that, the displacement becomes non-linear - it looks like "soft clipping" if you measure it with a microphone. It comes about as a result of voice coil length and gap length. Knowing Xmax is useful when determining how much power at a given frequency you can put into the system, given the box you've designed for it.

Xmax is nothing whatsoever to do with mechanical excursion limits. These are much larger than Xmax - typically twice.

I stand corrected. Of course you are right. It has been a while since I dealt with speaker parameters and forgot this detail, my apologies.

Running them at Xmax at 15Hz for a while is not testing them at their limits. The low frequency is chosen to ensure that hardly any electrical power is required to achieve that displacement, so there was no question of thermally overloading the voice coil. In normal use, they can be expected to be regularly pushed past Xmax - especially such small bass units (4").

The tests outlined are completely normal practice in the loudspeaker industry.

Again you are right and I made another error on this fact. I was remembering xmax wrong and made me infer that the speakers were abused. I was wrong.

And I quoted from a loudspeaker drive unit designer in my first post - where one mechanism was explained (spider resin). I know several loudspeaker drive unit designers BTW - I'm an engineer, not an "audiofool" - but the quote I provided was already in the public domain, so there is no problem referencing it.

There is plenty more evidence out there if you search for it - I'm not going to be made to feel guilty for only providing a limited amount of data as I assume everyone can use a search engine. All I wanted to say is that this effect is real - unlike a lot of stuff claimed by audiophiles. How audible it is depends on a lot of factors - I'm not about to get into that. And it's the "grain of truth" that I referred to in my opening post - I'm not claiming that headphone drivers are (or are not) affected in the same way - but you can see how the link could be made.

I agree that spiders can change their characteristics and more likely if they use resins and fiberglass or other cloth. The resin fractures and flakes and changes the whole mess. I still contend that this is not a good practice and better materials exist to do this job without these variables. I was not calling you an audiphool, I was referring to the obvious woowoo people. Your examples do show how one mechanical system can change from use. I know you are not claiming that headphones are effected the same way and yes I can see how the uneducated could make a spurious link that does not exist. It does no good for the believers to not have their views challenged, because they start some kickstarter program and make solar freekin headphone conditioners and sell them to the unwashed as well.

My apologies for confusing xmax with my old memory of working on speaker designs.

[ConKbot]

If something is going to change its characteristics through this kind of "break in" procedure then it isn't suitable as any kind of long term use. The idea behind designing a voltage reference is that it is reproducible, reliable, and predictable. If the material changes properties durng use, then it is not very desirable.

People who think that voltage references or oscillators need a break in are fooling themselves. They need to ask themselves this question: If the components change so much during break in, how do they magically stop changing after this alleged break in period?

Another: If they change properties so drastically during break in, how long until they change beyond being "good" again or utterly fail from the same change in characteristics?

This isnt specifically directed at Lightages, ive seen plenty of good content from him, just in general, they are a good example though. Or even at this specific topic.
Lets see how some of these statements fare if we change it to something we know a bit more about


Its a mechanical thing, mechanical things do break in a bit after manufacture. If a knob on a power supply is really stiff when its bran new, what would you do? twist it back and forth a few times and see if it smooths out? And what if after a few rotations it loosens up and is fine. Will you worry about how long till it gets sloppy?

Is a 100-500 mile break in on an engine complete bs by the manufacturers when you'd expect (at least the long block) to last 150k-250k miles?

Yes, we get it, audiophile stuff is funny, and a very large portion of the high end stuff is utter BS.  Will a woofer or tweeter brand new from the factory be different in response after you run it at near full power with broadband noise for 100 hours?  I'd suspect so.   Will a headphone where the diaphragm is just a thin little mylar sheet change?  I'd be more dubious about that. 

Everyone is so quick to see anything remotely audiophile, and then they like to jump all over it, post a bunch of crap just so they can show how much smarter than the dumb audiophiles they are.  Without even considering there may be a small sliver of merit where the audiophile junk came from. 

Like seriously, I've always considered making a nice DAC + headphone amp as a project of my own, but I wouldnt even post it on this forum, let alone ask advice about design, because the anti-audiophool nutters would be the majority of the posters in the thread.

[dannyf]

Everyone is so quick to see anything remotely audiophile, and then they like to jump all over it, post a bunch of crap just so they can show how much smarter than the dumb audiophiles they are.

On that front, the audiophools and audiodicks are not that much apart: they all wanted to make a religion out of half-baked science to show off their supposedly "good knowledge".

What they forgot is that the moment they opened up their mouths, they had removed any doubts about their ignorance.

[Mark Hennessy]

<snip>

My apologies for confusing xmax with my old memory of working on speaker designs.

Thank you for replying; much appreciated

For what it's worth, the spiders do settle down pretty quickly from new, and they are pretty stable over many years. As loudspeakers age, problems tend to be more related to the surround - especially PVC and other plastics (e.g. several BBC designed bass drivers had terrible problems with this - easily proven with the "hair-drier test" - but this is going back 30 years or more). Rubber surrounds can change with age and they can be temperature sensitive, and of course, foam rots away. The surround (and how it's glued to the cone) makes more difference to the sound than one might imagine.

It's understandable that transducer design might seem rather unscientific to some electronics engineers. But that's the nature of the beast, and that's what makes it so very interesting