Test: Burn In and Production Variations

A rare opportunity has come up to compare to units of the Audio Technica M-50 headphone, both in stock condition. One headphone has clocked hundreds of ours of, while the other is brand new from the box. For this test, both headphones are plugged in at the same time to both headphone outputs of the Grace m902 DAC/Amp.

Are the two any different? Is the difference significant enough?
Here is what I found:

  • The new unit significantly has a more closed and narrower soundstage.
  • The new unit presents more prominent treble.
  • The new unit presents a more forward vocal. I actually like this rendition better.
  • The new unit’s frequency extension is less smooth on both ends.
  • The new unit’s bass area is significantly less clear in texture.
  • The new unit’s bass punch is stronger.
  • Surprisingly, the new unit’s bass is not exactly more boomy than the old one.
  • The new unit has an inferior instrument separation.
  • Playing a test tone, the new unit is ~1dB louder than the old unit. (I used a 440Hz, 1kHz and a 4kHz continuous tone)

The difference is significant enough that I can tell immediately if I’m listening to the new unit or the old one, even without looking at the mark that I made in the cable to differentiate the two.

Now, the brand new M-50 was then put in for a several hundreds hour of burn in, and after a few weeks I went back and re-did the comparison.
This is what I found:

  • There is an improvement due to the burn in, with the new unit now being smoother and less constricted, having a better instrument separation. If the new unit was inferior in instrument separation, now it pretty much equals the new one.
  • However, the two headphones still sound slightly, yet noticeably different. The new unit has a more forward presentation. More forward mid and low treble, and punchier bass, where the old unit is noticeably more laid back. Playing some mild rock tunes, the new unit carries the energy of the music better, where the old unit sounded less focused and more laid back.

The difference is very interesting, and me and Hadi thinks that the different production batches account for more difference between the two headphones than the burn-in did. Although the burn-in makes the new headphone smoother and improves the technicalities slightly, the different production batch literally gives us two slightly different versions of the M-50 sound. I asked some other enthusiasts to listen to the two fully burned M-50s. Some people can notice the difference, and some other cannot. So clearly, we’re talking about very subtle things here. And yet the difference due to the burn-in is even more marginal than the production batch difference. Personally, it is very hard for me to note the difference, had I not have the second M-50 to compare with. I think this explains why a lot of people consider burn-in as more of a placebo effect. Yes there is a difference due to the burn in, but it’s very slight. And I do think that placebo plays a bigger role here than what actually happens physically with the drivers.

But of course the effect may be different from different headphone models. And since there is no way that I can do the same test on all the different headphones, anyone can still come up and claim that a 1,000 hours turns his headphone into a giant killer.

Test: Burn In and Production Variations
5 (100%) 2 votes

  • iyayy

    good to know there are somethings done to compare burnin result.

    im using an Audio-Technica ATH-W10VTG. the condition was very mint when i got it, can safely say it’s almost unused. (new leather condition)

    now here’s the interesting thing.
    when i got that headphone,
    it sounded almost the same to a 1.5yr old Audio Technica AD300.. in fact, the AD300 is slightly superior in some areas. comparison was done unamped.

    after clocking 1000hr on the headphone, the ad300 is definitely below the VTG in sound, again unamped comparison. On amping, the VTG left the AD300 years ahead.

    I am lucky to have a friend that owns a 13year old VTG as well. comparing my unit after 1000hr to his.. the difference in dynamic strength, body, separation, smoothness, etc is very evident. Even friends who are not familiar with both headphone can tell the difference in sound. Amping would only show more weakness on my vtg.
    Later I re-did a comparison after mine has clocked 2700 hr recently, and found that my VTG is closer to his VTG, compared to earlier. but it is still not as refined.

    U may well call it placebo effect.. or whatever. i also have a crossroad woody2 (1.7k hr) which sounded totally different than a brand new unit, my younger bro has a crossroad woody1 that sounds almost flat compared to a very very bassy new unit, a hippo VB which shares similar effect. so i chose to belive that burnin does have an effect, but varies on different headphone and drivers.

    of course the effect is varied depending on drivers; on FA eterna i didnt hear any improvement after 250hr; was up to 700hr before i sold it. of course this would not be valid for BA iems, but BA iems also takes about 10hr to settle down, initially all of them are very very harsh.

    • Thanks for sharing your comparison results, iyayy. Can't say anything much until after I've listened to the different headphones you mentioned. What's interesting is that, as in the case of my two ATH M-50s, production variations may also be causing the differences.

  • laon

    Finally… I’ve been waiting review like this to approve/disapprove Burn-in, still I do believe the upgrade differ from headphone to headphone, and some do show incredible change before and after burn-in, imo.

    Thanks Mike. 🙂

  • iyayy

    I also agree with the production variations as well. there are some that sounds better than what my memory recalls after claiming warranty, which is supposedly not valid because i should have been used to the smoother burned-in signature of the older ones. Seems like some manufacturer quietly improves their product.. eg, older senns vs new senns, or maybe they simply just acquired better skills or knowledge to assemble the cans to improve it. well as long as there is improvement, it is a good thing.

  • laon

    hmmm anyway to identify production batch?

    • @Laon: I'll try to look for it. Can't really see anything obvious though.

  • Kelvin

    Mike…this article needs a lot of cleaning up, man. Lots of confusing typos everywhere.

    • Thanks Kelvin. I too had that feeling when I wrote it. I'll try to re-edit some parts to make it more readable.

  • glac1er

    I've taken a listen to these 2 M50s that Mike reviewed, before and after burn-in. They sound a bit but noticeably different; it's easy to pick out the difference even if you do a blind test. If you can detect different sound between different cables, you are a lot more likely to detect the sound difference between the two M50s. I also think that the production variance is a much bigger factor to the difference between the two M50s than burn-in.

    Safe to say that I like the new unit (more bodied) version a lot, and a bit lukewarm to the slightly more clinical older unit. As the M50s are fairly neutral, I would call the newer M50 is neutral to a bit warm in the mids; on the other hand, the older M50 is neutral or even slightly cold in the mids.

    The difference is subtle, but it's noticeable and enough to make me say that I'm very likely to buy the more bodied M50 with my own money, but I'm not interested in the more sterile M50.

    I think this will be a big issue as every M50 owner is probably not listening to a completely similar sound.

  • Pingback: Suggest cans with budget of 15k()

  • olor1n

    Hi Mike, a few on Head-Fi are concluding that this article highlights the arrival of a newer but inferior version of the M50. I believe the intent is more to focus on the minuscule differences in production batches and the even more minute effect of burn in. Can you please clarify if you do indeed feel that AT have slipped an inferior into the market?

    • There is a slight loss in technicalities, yes. But overall me and Hadi prefers the newer version quite by a large margin. The midrange is more engaging — and that makes a lot of difference when listening to music. So I wouldn’t call the new one as “inferior”.

      • glac1er

        Without more samples, we can only speculate if the production variation is consistent and predictable. It might not just be due to the fact that one of them is a newer production.

        • True.

          It's funny how one little thing can make or break a headphone.

          A few weeks ago I took a friend to audition the M-50 at a local store. I suppose it was the "old" variants. Then a few days ago I happen to have my M-50 (the newer one), and I let him try it. His comments was "this M-50 is more engaging than what I remembered the last one to be".

          That was not an A-B situation, and over the course of several weeks. What's more, this guy is relatively new with headphones. Frankly I was surprised to hear how he was able to track down the difference with such accuracy, and over a period of several weeks.

          The difference must be more significant than I thought…

  • Jeremy

    Hi Mike,

    Do you have any information on the new colorfly? I have emailed the Colorful company and have received no reponse. The new player looks to set a new stardard in the DAP market. Thanks!

    • Jeremy, I've came across the Colorfly player a few months ago but has actually forgotten about it until you asked about it. I'm sending them an email. 🙂

  • Jeremy

    Thanks Mike

  • HiQualiT

    from what you said im liking the new batch, how would i go about making sure the one i order is the newer sound version?

    • Mike

      A few of my friends who bought M-50s recently has been getting the newer version consistently. The older version that I have in comparison was purchased some 2-3 years ago. I think it's safe to say that if you're buying from a store that has a lot of sales volume (Headroom comes to mind), the M-50 will probably be the newer batch.

      • HiQualiT

        thanks man, i also had the same idea, but didnt realize how old the old ones were, the headphone world just became known to me not even 2 weeks ago.

        • Mike

          Yes, I'm quite confident most of the big stores would probably have the newer version by now.

  • Jeff

    Hey Mike,
    Any recommended tips for the burn in process? Also, upon recabling my HD650s is there a need for burning in the cable? As I have not had the pleasure to listen to so many different setups I figure you would be able to enlighten me on the subject.

    All best,

    • Mike

      Hi Jeff,I personally just let it run with some music playing on medium volume. Some people use special methods for burning in, but seeing how little the burn in actually make a difference, I really don't think it matters how you burn it in.

  • Kcyoung3888

    I’m using the ATH-M50 with Fiio E7 DAC/Amp. I was entertaining the idea of upgrading the DAC/Amp. Will I have better result adding the E9 to my E7 or go with the Audinst HUD-MX1? Any comments will be helpful. Thanks!

    • Anonymous

      Hi Kcyoung, I think you can go with either the E7/E9, or the Audinst. Both have slightly different sounds, but should work just as well for the M-50.

  • himan360

    This is wonderfully done. However I’d like to see a frequency range chart that compares both the newer batch and the older ones on the same graph. That be terrific.. don’t you think?

    • Anonymous

      That’ll be terrific, but we just don’t have the facilities to do the graph. Sorry.

  • Pingback: O Famoso Burn-In « MIND THE HEADPHONE()

  • Diobrando


    I’ve bought a pair of Superlux 668-B.What sounds/files d’u suggest to play for an optimal burn-in?I wanna mantain the equilibrium amongst the frequencies.What is your burn-in playlist?
    Thx and keep it up. This site is a precious mine of audio stuff infos 🙂

    • Anonymous

      I know that some people have certain methods for burning in their headphones. In my experience however I can’t really tell the difference between a pink-noise burn in to a standard playlist burnin, and I’m pretty sure that nobody has done any tests comparing the effects of different songs for burning in a headphone. I don’t think you have to worry about it too much. Just let it run for about 12 hours and it should be good afterwards.

  • RayJuodas

    Enjoyed this article very much (as well as many others on
    this site), thank you!


    This might come as a surprise to many, but I have found that
    headphone ear pads play a major role in the perceived frequency spectrum and
    the sound signature of the headphone. I have had 3 pairs of ATH-M50 (1 Old one,
    2 brand new pairs) at one point and compared them carefully between themselves.
    There’s a slight difference between all of them on its own, probably because of
    different batches or manufacturing fluctuations, but the most obvious trend showed
    up when I switched the pads between the units, and it closely matches the one
    you describe: M50 with new pads sounds more “rubbery”, with more pronounced
    lower treble, a bit subdued mids and boomier bass (because of the aforementioned
    treble+mids trends), while the older pads make the sound fuller and not as
    extreme, I prefer the latter by a large margin, the sound is quite similar to
    my Dynaudio BM15 passive monitors, and I love that sound immensely. This is the
    full review of 7 closed cans I wrote a week ago or so, hope you’ll find it constructive
    and some probably will be stunned to some extend 🙂 Cheers!



    • Anonymous

      Thanks Ray,
      What you find totally makes sense. The pads are a big part of the acoustic space in headphones and any variations on the pads will alter the acoustic properties of the headphone.
      I’ve written somewhere (I think it was the Sennheiser HD580-600-650 article) that when the pads are softer (worn out) it makes the sound more forward and less dark. Likewise with the Grados, when you wash the bowl pads, they get softer and the treble is not as harsh as they are on brand new pads.
      That looks like a very good comparison you have on Head-Fi. Also nice to see that you included the Beyer DT231which a few readers have been asking me about.

  • Daniel_juke

    Hi Mike ,

    What would pair best with M-50 

    E7/E9 , E17 , E10 ,MX1 ,  HRT MS2

    • The E17 is currently very highly recommended from me. The HRT MS2 is very good but you need to add in an amplifier.

      • Daniel_juke

        Ok…If I go for the HRT MS2 route then , what would you suggest as  an  Amp for around 150$

        • For $150? Try the upcoming O2 amplifier from JDSLabs.

          • Daniel_juke


            Would you prefer ‘DAC’ of E17 over HRT MST2 ??

            • Daniel,
              The MS2 has the better DAC.

  • Alex

    I bought the m50s because i thought they would be more neutral and bass heavy than my grados. However, as of now (with only 4ish hours of burn in) i find that the m50s are even more forward and treble heavy than the grados, with little improvement over the grados in the bass. Can i expect this to improve?

  • To me the difference seemed to be with the ear pads used in 2010 models. The newer ones seem to have much class but at the same time they are more fatiguing. Also in newer pads I think that they used some sort of a liquid based substance which smells more or less like break oil to me. don’t know, just my guess

  • ZeDestructor

    Hello Mike.

    Recently My ATH-M50 headphones fell off my desk and snapped the headband (that is snapping one small piece that limited the swivelling of the earcup) so I had to get a new set of ATH-M50s.

    So I did, and this time I got the ATH-M50S. I immediately tested them and found a reduction in soundstage. Burn-in had no effect, but swapping in the drivers and inside padding from my ooold M50s (original release blue box, and yes, I blindly bought mine before any reviews were online) brought things back to normal.

    To me, it is clear that there were changes to the inside pads and/or drivers, while everything else remained the same.

    Either that or the batch my original was made with got *REALLY* lucky and had an epic set of drivers.

    Now to stretch that headband….

    Note, I used the same Shure SRH840 earpads, so earpad changes are not a factor in my test.

    P.S: The 3m straight cable feels loooooooong, but is much more flexible than the original straight cable, but hasn’t lost any of its durability going by the indentical thickness of the cladding.