This is Part 1 of the Controlled burn-in with predictable results for headsphones .
Opinions on whether effects of burn in on various parts of the audio systems are real or placebo are divided. There is no denying we get accustomed to a particular sound signature and then tend to do quite well at distingushing listening through that device for differences in either other gear or various recordings.
The effects of out of the box vs burnt in headphones are not day and night differences as evidenced by quite a few objective measurements, that although they differ among themselves, were always the same for measuring the headphone »before« and »after« the burn in process. Variation of about 1 dB or so have been observed and although these are rather small, by any means they are not inaudible, particularly if the change occurs in the midrange where our hearing is the most sensitive.
Judging from frequency response alone, one might conclude everything is in order and the performance of that headphone would allow for accurate reproduction. There is a hidden defect that is very easy to overlook in the frequency response graph. Fundamental resonance. http://en.wikipedia.org/wiki/Resonance
That resonance may well be very well damped or in technical terms, it has low factor of quality, (in further text) Q. However, there is always a 180 degree ( or close to that in real life ) phase shift occuring at the resonant frequency. With sharp ( high ) Q resonance that shows up clearly in the frequency response graph as pronounced peak, the range of frequencies affected by phase shift is relatively small – exactly opposite is true for low Q resonnces that are hardly visible in the frequency response, but the phase response shows anomally spread over several octaves above and below the resonance frequency. Both conditions lead to audible colouration and in practice a mean condition between the two extremes in Q are most commonly used.
The best way to deal with this fundamental resonance present in any headphone ( or any other electroacoustical transducer for that matter ) is to place it above or below the frequency range of interest, in our case the commonly accepted range of hearing in humans of 16 Hz to 20000 Hz. However, only the costliest of principles and actual realization in designs commercially available meet or exceeed this criterion. Vast majority headphones exhibit its fundamental resonance within the audio band, generally between 16 and 150 Hz, with resonance nearing lower frequency limit of hearing with increasing price. Generally, you do get what you paid for.
The fundamental resonant frequency of ( dynamic headphone) transducer is determined by the mass of the moving element and stiffness of its suspension. The mass is fixed and we can not do anything about it – and we do not want lower the fundamental resonant frequency by increasing its mass, as this would have detrimental effect on high frequency response. So the only course left open is to decrease suspension stiffness by enough to at least lower the fundamental resonant frequency within the audible range where it is less likely to get excited - if not below and outside of audible range.
How can we do that? By burn in – with precise specified signals that under close control allow to safely achieve our goal in the end. To use an analogy in sports – if you want to win a medal at the Olympics, you start to train/exercise at your current level, ever increasing its intensity/quality until, hopefully, your performance will surpass anyone else's – NOT trying to match top performance athletes' at your first training after it occured to you you would like to listen to your country's hymn with the medal around your neck .
If you do not have it already, you will need to download signal generator SineGen .http://www.tucows.com/preview/502787 I also provide the Wikipedia links for sine wave http://en.wikipedia.org/wiki/Sine_wave, triangle wave http://en.wikipedia.org/wiki/Triangle_wave, square wave http://en.wikipedia.org/wiki/Square_wave, white noisehttp://en.wikipedia.org/wiki/White_noise and pink noise http://en.wikipedia.org/wiki/Pink_noise. Please read all the Wikipedia links as I would like you to understand exactly what we will be doing with our headphones.
I could have easily started advertising headphone burn in and charge for my service. That would give you a »fish« ( and me some coin ) - old chinese saying has it if you give the hungry man a fish, you would feed him for one day – if you teach him how to fish, you have fed him for life. I prefer to learn you how to "fish" for the good sound instead.
I would like to raise the understanding of most head-fiers to another, higher level. There are phrases commonly used on head-fi that make me frown each and every time I read them. I understand where they are originating from – from the comment you are making it is clear that you can hear quite OK, yet the vocabulary used, and precision of that vocabulary in particular, leaves much to be desired.
Head-fi.org has become a very important organization with great influence on the global basis – with the uprising of decent sounding portable gear, this has become great force to be reckoned with in the music/audio market of today, rivalling, if not already exceeding the sales for the home speaker based systems in total value – not to mention the music/software part of the bussines.
So, any education of new younger generations of music lovers and audiophilles alike we older guys are willing to share should reap a good crop in the future – educated choices made as a direct consequence of it should go a long way towards our common goal – perfect reproduction of a musical event. If you feel a bit intimidted by the slightly academic approach used – don't be. No grades will be given – but the more you will understand, the more you will be able to enjoy your music in the end. Not totally devoid of the budget involved, but always trying to get the most for your hard earned money.
In Part 2, the actual process of controlled burn in will be presented. It will be posted in a couple of days – to give you time to download things required and digest the info in Wikipedia links for them to be able to sink in. For me, to try to find the online generator that most closely approaches what I actually used in the end; if I fail, I will ask you to help, more heads know more and are also able to find more. To use sports analogy again, present SineGen will take you to the nationals, you would not be competitive at the Olympics level. Still, it would outperform any form of burn in by music of whatever genre.
As always - enjoy your music !