[tranhieu]

Quote:

 AKGs manufacturing practices are far more likely to produce near-identical cans than not. 

May I have the statistics for the QC process? For some reason I cannot find anything in AKG's website.
 
Quote:

 
By the way, here is some data on speaker drivers breaking in over time (no shifting pads here):
http://www.vikash.info/audio/audax/

Again this test also does not conclude anything IMO. Only 6 samples available, and I don't get it why he used 30% tolerence for the test to begin with, which is a massively wide critical region for such hypothesis test. Plus what distribution is being used here? Parameters?
 
Statistical tests only work if they are carried out properly, with enough data and external factors being taken into account carefully. Otherwise they might even bring more misjudgement into the debate. 
 
Edit: if this test does not mean to be a statistical test, discard my comment above regarding the quality of the test.

 

[Head Injury]

Are the two K701 graphs on Inner Fidelity (the regular one and the one labeled Sample B) two different K701s?
 
If so, there are enough statistically significant differences in frequency response, distortion, and impulse response that one really can't say AKG produces near-identical headphones. At least compared to the differences measured in the first burn-in article.

 

[mikeaj]

Quote:

Again this test also does not conclude anything IMO. Only 6 samples available, and I don't get it why he used 30% tolerence for the test to begin with, which is a massively wide critical region for such hypothesis test. Plus what distribution is being used here? Parameters?
 
Statistical tests only work if they are carried out properly, with enough data and external factors being taken into account carefully. Otherwise they might even bring more misjudgement into the debate. 

 
Maybe I'm missing something here, but the comment on 30% tolerance does not have to do with a statistical test of significance or a hypothesis test, but rather about the samples deviating from the nominal manufacturer's values.  I don't think this was intended to be a statistical test or any kind of conclusive proof.  And there's a separate issue of the audibility of changes, even if changes do exist.
 
Anyway, if you look at the individual results for each of the six drivers, the trend from 0 hours towards lower Fs / Qms / Qes / Qts values and towards a higher Vas value (and in each case, the trend is towards the manufacturer's spec) do seem pretty unmistakable.  It's hard to claim that no change at all is happening over time.

 

[tranhieu]

 
Quote:

 
Maybe I'm missing something here, but the comment on 30% tolerance does not have to do with a statistical test of significance or a hypothesis test, but rather about the samples deviating from the nominal manufacturer's values.  I don't think this was intended to be a statistical test or any kind of conclusive proof.  And there's a separate issue of the audibility of changes, even if changes do exist.
 

Fine, I got confused by his 30% tolerance region. If that doesn't mean to be a hypothesis test (I still doubt it) I will take back my comment above. 
 

 
Anyway, if you look at the individual results for each of the six drivers, the trend from 0 hours towards lower Fs / Qms / Qes / Qts values and towards a higher Vas value (and in each case, the trend is towards the manufacturer's spec) do seem pretty unmistakable. It's hard to claim that no change at all is happening over time.

Again, relying solely on those numbers doesn't help at all. They might suggest something, and that's it. I would prefer not making any claim at this stage.
 

 

[poikkeus]

Tyll's article suggests something that I mentioned in my FAQ (noted below) - that it makes common sense that headphone engineers would design their better phones so they would, with use, come closer to an expected sound. (This addresses a common question why headphones often seem to sound, not worse, but better after breaking-in.) 
 
 
 
 

 

[ocswing]

Quote:

Certainly when I hear people say "night & day" differences, then either they have faulty equipment or faulty ears. I believe that the vast majority of the burn-in effect with cans and speakers is actually burn-in effect of the owner's ears. However, I have not seen conclusive proof that burn-in effect can never happen (with some speakers and cans) and I am certainly open minded enough to accept that for some speakers and cans it is a possibility.

So Tyll, I am not arguing against burn-in effect, even though I believe in balance that it is unlikely. Some real evidence of it's existence would have been useful, but for me, your poor methodology and your jumping to conclusion based on assumption, has done nothing to help clarify the situation.

Maybe I'm being a little harsh on you Tyll, at this point in time I'm not sure of your motivation so I'm not deliberately trying to rip you a new one. Maybe you have good intentions but even so, in this instance, the old saying comes to mind: "the road to hell ....."

G

 
From the other thread Tyll made this comment in one of his posts, "It's now become the common belief that you won't know what your headphones sound like until they're burned-in. That's balony. While I could tell the difference between the two cans, they weren't much different. When you open a box of headphones and have a listen, that's pretty much what they're going to sound like. Anyone who says, "OMG after burn-in my new cans are night-and-day better" is full of hoooeee."
 
Your viewpoints aren't as far apart as you might think.
 
 

 

[Shike]

So basically the findings are this:
 
You may be able to tell the difference between two cans after extended use - and this is assuming it's not a difference in tolerances.  We can't say all headphones will experience mechanical change or that all won't, it's a matter of degrees and "possibility" at this point.  Fair enough, the burn-in argument for headphone drivers warrants more examination with this test to say the least.
 
 
I think what's most important here though is being overlooked.  How many people have been advised to keep headphones they didn't like, and furthermore convinced that they would merely like this purchase by putting unnecessary wear on them into the thousands of hours?  I understand telling them to drop their old headphones in a box and shove them in a closet till they really give the new ones a fair shake (adjusting to the new sound and all that jazz) - but people may have been rather disingenuous here and in other places to say the least ESPECIALLY in the case of the K701.  Don't get me wrong, I love the AKG 7 series - it's a bit more punchy in the mid-bass than the K601's I own while still being pretty balanced, but in general the amount of misleading information here regarding the untold night and day potential of this phenomenon isn't cool.  I'm glad Tyll has at least called BS on that much.
 
Speaking of tolerances though, I've been able to tell multiple pair of low hour Grado headphones apart before.  One may say the QA/QC isn't up to the same standards, but differences in tolerances certainly do exist.

 

[Willakan]

Yes, people do tend to attribute rather more than a slight loss of harshness to the AKGs "burn in" period. You should not...nay!...must not listen until 300 hours, as until then there is no bass, the soundstage is nonexistent and the treble goes round in circles!
In one respect, I wish Tyll had completely disproved burn in, as then the idiots that claim "night and day" differences wouldn't have a leg to stand on (not that they have much to stand on at the moment, but every little helps)

 

[SpaceTimeMorph]

It would be interesting to see a blind test done pre/post burn-in.  I can't see how manufacturers tolerances for headphones would be necessarily smaller than a potential difference in burn-in effects.  My own experience has taught me there is a huge difference in manufacturing variability in everything from screws/bolts, resistors, centrifugal pumps, etc... I think the manufacturing tolerances definitely needs to be taken into account for further tests, although I understand that wasn't necessarily the intent of Tyll's article.
 
Also, there's this article on speaker burn-on.

 

[fubar3]

Say, how come the manufacturers do not burn-in their audio devices before shipment?  If a product is certified as being ready for your enjoyment, then one is more likely to prefer that one over "here is a headphone, I hope it works".  I suppose a sealed speaker enclosure which has been shipped in an aircraft might need air pressure equalization much like your ears or water bottle after a trip.  But headphones.. I don't have any theory to explain it.

 

[The Monkey]

I have long been unconvinced of the existence of burn-in.  However, Tyll's article and testing are forcing me to rethink this position.  While I am not yet convinced, I do find the results interesting.  I wish there were a larger sample size and more trials, etc. but I understand that this exercise was never meant to be a "clinical study."  Regardless, it is useful data and I think Tyll's conclusions acknowledge that there is more work to be done to get to the bottom of this issue.  Further, I'm confused by some of the posts I have seen questioning Tyll's possible motives.  Simply put, Tyll is one of this hobby's "good guys."
 
Finally, to me, one of the most important observations made by Tyll in the article is the following: "I'm absolutely convinced that, while break-in effects do exist, most people's expressions of headphones 'changing dramatically' as a result is mostly their head adjusting and getting used to the sound." 

 

[Currawong]

Quote:

So basically the findings are this:
 
You may be able to tell the difference between two cans after extended use - and this is assuming it's not a difference in tolerances.  We can't say all headphones will experience mechanical change or that all won't, it's a matter of degrees and "possibility" at this point.  Fair enough, the burn-in argument for headphone drivers warrants more examination with this test to say the least.

This what I understand too. Some people though, it seems, only want it to be absolutely true or absolutely not for all headphones and don't seem to be able to understand this.
 

 

[poikkeus]

Quote:

Say, how come the manufacturers do not burn-in their audio devices before shipment?  If a product is certified as being ready for your enjoyment, then one is more likely to prefer that one over "here is a headphone, I hope it works".  I suppose a sealed speaker enclosure which has been shipped in an aircraft might need air pressure equalization much like your ears or water bottle after a trip.  But headphones.. I don't have any theory to explain it.

Read my informative, semi-amusing blog under this post for a full, contextual explanation. If you're looking for a shorter text:
 
- It's possible that some headphone makers might feel that break-in differences are slight
- Some headphone makers, like Ultravox, include paperwork that some might hear a difference in sound after using phones for a few days, but the sound stabilizes over tine
- To quote my blog: "One can understand why corporate support would be less than enthusiastic in admitting that their $300+ headphones weren't 100% perfect on arrival."
 
Also, for clarity, it's probably not possible to burn in headphones. But headphone "break-in" is a distinct possibly. Read the attached blog for the difference.
 

 
 

 

[Rdr. Seraphim]

Re Tyll's motivation, what does it profit him anyway? Is he gonna start a Burn-in Business or something? (Yah, I can see that!) What does he have to gain by making such a claim? What's the fear in a little experiment that shows that there might be a difference with use? Don't most company's already provide a 30 - 60-day return policy anyways? 
 
Rather, what's the motivation for someone questioning someone's else's motives to begin with? We're not judging anyone, right? If on the other hand a tree bears bad fruit, well, there are plenty of fireplaces for that.  
 
Quote:

I have long been unconvinced of the existence of burn-in.  However, Tyll's article and testing are forcing me to rethink this position.  While I am not yet convinced, I do find the results interesting.  I wish there were a larger sample size and more trials, etc. but I understand that this exercise was never meant to be a "clinical study."  Regardless, it is useful data and I think Tyll's conclusions acknowledge that there is more work to be done to get to the bottom of this issue.  Further, I'm confused by some of the posts I have seen questioning Tyll's possible motives.  Simply put, Tyll is one of this hobby's "good guys."
 
Finally, to me, one of the most important observations made by Tyll in the article is the following: "I'm absolutely convinced that, while break-in effects do exist, most people's expressions of headphones 'changing dramatically' as a result is mostly their head adjusting and getting used to the sound." 

 

 

[ph0rk]

Quote:

I think what's most important here though is being overlooked.  How many people have been advised to keep headphones they didn't like, and furthermore convinced that they would merely like this purchase by putting unnecessary wear on them into the thousands of hours?  I understand telling them to drop their old headphones in a box and shove them in a closet till they really give the new ones a fair shake (adjusting to the new sound and all that jazz) - but people may have been rather disingenuous here and in other places to say the least ESPECIALLY in the case of the K701.  Don't get me wrong, I love the AKG 7 series - it's a bit more punchy in the mid-bass than the K601's I own while still being pretty balanced, but in general the amount of misleading information here regarding the untold night and day potential of this phenomenon isn't cool.  I'm glad Tyll has at least called BS on that much.

 
I have to agree - especially in light of the fact that most of the suggested burn-in periods place the new owner well outside the normal return window for the headphones, leaving them stuck with them.
 
I'd go so far as to say that if you can't stop hating them after a couple hours, they should probably get returned.
 
Further, the tolerances thing is pretty big with some headphones. I have a pair of Beyer DT250's I love, and went through three pairs to get a second pair that sounded similar. 
 
Otherwise, pretty much everything will break down over time, and use might accelerate that (and you might stretch headbands/compress earcups, etc).