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Testing audiophile claims and myths

Discussion in 'Sound Science' started by prog rock man, May 3, 2010.
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  1. Phronesis
    To be fair, I should have said that it sounds like crap to me, but it’s plausible that it really does sound good to others. But when people say they had problems with the sound initially, and the sound got much better after burn in or changes to expensive cables, I do think they’re fooling themselves.

    We talk about expectation bias with DACs and amps, but I think it’s a real issue with headphones too.
    monsieurfromag3 likes this.
  2. WoodyLuvr
    When I brought home my new Audeze LCD-2s (circa 2012) I was enraptured... eight (8) hours later I was nearly in tears with agony and utter dismay. After burn-in, both driver and human head, the LCD-2s became more and more uncomfortable (too heavy, sweaty, and clampy) and they honestly did not sound much better than my B&O H6s (maybe due to their weaker, shallower bass???). I also found the imaging of the LCD-2s to be only ever-so-slightly better than the B&O H6s. I was very sad. Burn-in was surely to blame.

    I gifted them away in early summer 2017 as they were just gathering dust... I must admit they were a horrible impulse buy.
  3. Phronesis
    Sometimes, we can be initially impressed by a new and different sound, maybe with strong bass or highs, but over time the deviation from neutrality is perceived to be excessive and becomes annoying. Or as we listen to more tracks with a headphone, that may reveal problems that weren’t evident with our initial test tracks.

    The process of evaluating a headphone is a whole topic in itself, and I personally don’t find the process to be easy.
    Last edited: Jan 3, 2019
  4. KeithEmo
    Speaker drivers, which includes the drivers in headphones, are mechanical... and they have flexible suspension parts.
    Cone speakers usually have the roll shaped edge seal, which you can see, and a flat disc shaped suspension device attached further back, near the voice coil, called a spider.
    Dome tweeters, and many headphone drivers, have a single edge roll that acts as both seal and suspension.
    And, in planar tweeters and headphones, the membrane itself flexes near the edges to allow it to move forward and backward.
    This mechanism acts both as a seal for air and as part of the return spring that brings the diaphragm back to its center rest position after it stops moving.
    The resonant frequency of any moving mass, like that diaphragm, is determined by the moving mass, and by the strength of that spring force.
    (For a given mass, the less powerful the spring, the lower the resonant frequency.)
    In a speaker or headphone, the edge spring typically starts out a bit stiff, but softens a bit after being flexed back and forth for the first few hours.
    Then, once it's broken in, it remains pretty much the same over the life of the product.
    When you design a speaker or headphone, the design parameters you use for the driver are the ones it will have for most of its life (those are the ones on the spec sheet).
    So, for the first few hours, until the suspension softens up (breaks in), the suspension spring is a little too powerful, and so the driver parameters are a bit off.
    (Since the parameters are wrong for the first few hours, and correct after that, we assume that the sound after the speaker breaks in will be "right" or "what the designer intended".)

    The softening process can take anywhere from an hour or two to a day or two - and affects some drivers much more than others.
    (Although you can speed it up by playing test tones for a few hours it will happen by itself with normal use anyway.)

    This effect can be significant with some drivers and barely noticeable with others.
    It tends to be especially noticeable with ported speakers, where the cabinet tuning is specifically matched to the speaker's resonance, and a mismatch can cause noticeable shifts in bass response.
    However, other drivers can also exhibit a slight, and possibly noticeable, difference in sound over the first few hours.

  5. bfreedma

    I assume you’re about to post evidence supporting the above being audible. I’ve seen limited examples in larger drivers (woofers/subwoofers), but none for smaller drivers measured over hours or longer. Looking forward to seeing measurements.
  6. Phronesis
    To me, if some headphones need a few hours of burn in to sound their best, it doesn't make sense to me that manufacturers of expensive headphones wouldn't do the burn in themselves before boxing up the headphones, to avoid consumers and reviewers auditioning the headphones when they're sound is suboptimal due to lack of burn in.
    Killcomic likes this.
  7. bfreedma
    Exactly. Same with speakers. The manufacturers I’m familiar with spend enough time with the drivers/speakers in the QC process to account for whatever minimal mechanical break in may (or may not) occur.
  8. castleofargh Contributor
    I'd like to see evidence before conclusion from time to time.
    my own limited attempts at confirming audible change in headphones, left me with changes from the driver(and driver alone!!!!!!!!) that could just as well be the margin of error of my setup. but those experiments also gave me clear evidence that many things disregarded by audiophiles in casual listening "tests", do affect sound in an obvious way: pad compression, position on the head, volume change, memory flaws, new toy effect. anybody supporting the idea of audible burn-in on their headphones, please try at least to make us believe that you have accounted for those other variables before cherry picking burn-in as the cause of any and all impressions of change over time for no legitimate reason whatsoever.
    failure to do at least that will always have me believe that my interlocutor is clueless no matter what really happens to the headphone.
    gargani and Phronesis like this.
  9. bigshot
    I did a response test with tones side by side on a burned in and brand new set of Oppo PM-1s. I couldn't detect any difference. But I imagine high end cans with tighter tolerances are less likely to change.
  10. KeithEmo

    I've seen plenty of measurements showing how larger drivers change their parameters over the first few hours... sometimes significantly.
    And no speaker designer I know would take measurements without letting the driver run overnight first.
    (Obviously whether a given measured change will be audible depends on many factors.)
    Since the drivers in headphones operate according to the same mechanical principles, it seems reasonable to assume that they would be subject to similar effects.

    However, very few folks have bothered to attempt to perform any proper tests, and there seems to be little interest in doing so.
    (Even headphone manufacturers seem to disagree about whether the effect is sigificant or not.)

    Of the few tests run - there seem to have been a few that concluded that there are measurable differences - at least with some headphones.
    However, none were done with any significant number of different models, or with more than one or two test subjects.
    And, even then, the results of listening tests seem to have been inconclusive.
    Headphone sound is also affected by their fit, which changes slightly every time you put them on, and makes comparisons even more difficult.
    (It's also possible that, as with full size speaker drivers, different models may be affected quite differently.)

    Therefore, with a specific model of headphone, I wouldn't presume to know if there will be any sort of burn-in effects or not.
    If I were trying to take measurements, I would probably allow a headphone to burn in overnight, simply to eliminate the possibility that they might change.
    (If a change occurs after you take measurements, then your measurements will be wrong; but, if no change occurs, then no harm done.)



    Since the construction of headphones varies considerably...
    I suggest that anyone requiring a specific answer test the particular model they are interested in...
    (Personally I don't care enough to bother.)

  11. Phronesis
    ^ Seems reasonable to give headphones burn-in time just in case the sound changes, but doesn't seem reasonable to conclude that the sound changed due to burn-in unless there's evidence which supports that conclusion and rules out other factors. Audiophiles typically never have such evidence, yet the belief in burn-in is rampant. Most people trust their ears way too much.
    gargani likes this.
  12. hifip
    Anyone with any queries, take a look at the pro audio world. There lies your answers. The people who make the music we love so much don’t buy into any of the BS like the hi-fi world does.
  13. nickosiris
    Yup. In my humble opinion it's possible to be entirely correct and toe-curlingly obnoxious at the same time.
  14. bfreedma

    Here we go again - you make a claim then refuse to support it beyond posting that "you've seen plenty of measurements", none of which you can produce. And that you "don't care enough to bother". So essentially, your original post seems to be forum trolling (since you don't have supporting evidence and don't care enough to bother).

    What makes this a bit more interesting is that your organization builds and sells speakers. Does Emotiva "burn in" their speakers or not? If so, then there must be a reason and you would presumably have the data to support it - both for initial burn in and long term use. A simple set of pre and post burn in FR graphs would be a great start. Adding a CSD waterfall would be even better.

    Since you claim this phenomenon is "especially noticeable with ported speakers" and your company produces ported speakers, you surely must have supporting data...
    Last edited: Jan 3, 2019
    taffy2207 and sonitus mirus like this.
  15. Killcomic
    To be honest, mine sounded really bad too when I burnt them in the oven for 8 hours.
    gargani likes this.
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