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Burn in time, myth or fact???

Discussion in 'Sound Science' started by sonoman, Jan 9, 2006.
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  1. castleofargh Contributor
    a lot of things affect this frequency response, and burn in is without a doubt not the cause of what we see. this is measurement malpractice in effect, not burn in. the low end is nonsense, even a failed seal probably wouldn't wobble like that. IDK if it's picking up noise(seems too regular for that), or if it's a messed up measurement setting that can do this? if I had to guess, I'd bet on having the device is on the desk, and he hit the desk with his hand while recording? depending on the output levels, just clicking the mouse to start the sweep could be enough(REW offers to set a delay between when we click and the actual start of the sweep, he probably could use that). but then again, trying to measure down to 2hz with an IMM-6 is brave. with the roll off, there is no way to get the necessary dynamic to avoid measuring noise in a quiet room while avoiding to distort the midrange by pushing it too loud.
    in any case the low end is obviously BS, the rest could be a change from placing the IEM 1 millimeters deeper.

    something as small and critical as trying to measure driver burn in, needs a test organized for it, not just sloppy measurements a few days apart. for starters, tips should be removed entirely when the objective is to measure variations. they're too much of a joker variable. and the IEM shouldn't move at all during the process, or it needs to have a sure way to position it exactly the same way for each take. the upper mids and trebles are reasonably close for typical FR measurements, a sign that he did try to get a similar position(maybe by measuring and moving until the result was close to the original?(that would defeat the purpose for this specific test thought). but it's nowhere close enough for when trying to demonstrate something like a variation over time. which based on my own experience with a bunch of IEMs, generally doesn't register on FR graphs aside from getting a clogged damper(filter) with dust and earwax. or if a change does show up, in my measurements it was so small I couldn't clearly isolate it from typical measurement variations(you measure twice in a row without changing anything or waiting and still you get some super tiny changes when zooming in on the FR, that's the sort of changes I measured for IEM burn in the few times I tried so far).
    up late likes this.
  2. bigshot
    Well, we can still dream, can't we?
  3. dhruvmeena96

    I was not even telling about ultra low frequency....see near 5kHz.

    And it was confirmed that the depth of insertion and other factors were tried to be kept same....

    I wrote

    " if it has to get burn advantage, it will get it within the first 50hr, if not, then we are wasting time".

    I also didn't use to believe in burn in but after seeing old data, it is correct.
    And I also wrote, new drivers don't get effected by burning.
  4. bigshot
    He should have not touched it while he was doing the burn in. The way it's hooked up can have an effect on the response. How did he explain the fact that the two charts were made at radically different volume levels?

    He should probably try this test again and not change anything until the burn in is completed. He's introduced too many chances for things to change for reasons completely unrelated to burn in.
    Last edited: Jun 7, 2018
  5. dhruvmeena96
    I will check that
  6. castleofargh Contributor
    if all it took to validate burn in was to grab a mic push an IEM down a tube before and after to record a sweep, I wouldn't be so suspicious about burn in testimonies as I've done that myself a bunch of times over the last years. the only clear correlation I found on the FR is that the more I control my experience between measurements, the fewer variations I could record. to the point where I haven't been able to record a clear change in any of the last new IEMs I could get my hands on(admittedly mostly BA drivers). on the last new headphone I got, just five minutes withe the pads under pressure from the natural clamping on the cheapo "dummy head" I have, was enough to significantly alter the FR, making my measures irrelevant when it comes to driver burn in and of course, strongly suggesting what has been proved many times over, that placement on the head and pads changing shape, texture(from sweat, wear, whatever), are usually the biggest measurable change on a headphone. so even people who weren't delusional about their subjective impressions and memories of the first sound, usually blame driver burn in for stuff it didn't do.

    obviously me measuring a few IEMs and finding no clear evidence of change from the driver, doesn't mean some other IEMs won't change over time. but it certainly made me more demanding when it comes to what I would consider evidence of burn in. and even more so for what I would consider evidence of audible change caused by burn in.
    it also stopped me from assuming that every piece of evidence I saw for speakers could just be applied as is on headphones and IEMs. when you think about it, many variables are different, materials, shapes, sizes, weights, force applied on the material. the excursion goes nowhere as far as it would of a reasonably large speaker. so the flexing reaches a smaller angle, don't you think that alone warrants caution about drawing conclusions on headphone and IEM based on speaker data?

    otherwise, no reason to take my previous post personally, I think. I quoted your post because it contained the graphs. but you're not the one who measured this as far as I know.
    up late and dhruvmeena96 like this.
  7. thisisnotaboutagirl
    I think some headphones need it more than others. I've heard about headphones becoming a bit more efficient to drive after a few months and this is accounting for new pads.
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