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# Headphone Burn-in - Page 5

Here's something that i am upto

It's basically a fixed amplitude detector. The test material has been to attached to a coil (76Ohm) which is constantly energised. The magnets are elctro-magnets configured to generate forced sine vibrations on the test material. The amplitude is calculated by the laser detector which can only detect a fixed amplitude. This system will be left operational for 100+ hours and the amplitude will be measured again (maximum value). This HAS to be done in STP at 100 hours things do get hot.

after this a sample will be cut out and it's value of Y and k measured, (as a ratio of the older values) hopefully if we get significant ratios this might prove that burn-in in fact is a physical process.

but then, i can only hope :)

Since you said that the laser detector can only detect a fixed amplitude, do you sweep through different amplitude values to get a sense of how much the sample material is oscillating?

So let's assume you see a change in amplitude over the 100 hours of testing. The real test to see if burn in is true would be to turn off the oscillations and let the whole system cool down. Once that happens then turn the machine on again and record the oscillation amplitude and compare.

I'd guess that it will be the same as the amplitude you measured initially.

My proposed experiment might not be valid with your system, because I'm not completely sure how it works from reading your description.

Interesting

Note: these are NOT real world values the system was subjected to over 1167mW way above what normal headphones handle.

Let me explain this, I'll take the original value to be 'x' and the new value to be 'y' the data here will be y/x only a ratio.

Data is not sufficient, ratio's are running in 10^(-4) which is beyond the least count of the system.

Amplitude (from diametric normal , sine wave 2.2Vp-p)

Original = 3.6678mm register value (RAW DATA not rounded off) 3X2220912**

New= 3.6677mm  register value (RAW DATA not rounded off)       3X2220953**

** raw register values from the APU not to be compared mathematically. these can also be due to temperature variations and even the limit of the accuracy of the system.

Conclusion: No Effect! woot! well, something but as for amplitude modifications at fixed frequency sine wave response was not changed after 97.6 Hours of exposure to energizing.

Ambient values:

Temperature : 25C---28.7C

Pressure: Standard value

Audio Isolation: up to -32dB soundproofing and damping

An objective and undeniable reason as to why the sound of headphones changes over the 1st month?

As one wears a pair on new headphones, the foam (or any other material) inside the pads usually become softer and more compressible, as a result, after some time of use the drivers of the headphones come closer to your ears. Would it be enough to change the reflections of the soundwaves on your ears and thus change the sound of one's headphones?

Edited by khaos974 - 4/17/11 at 5:50am
Quote:
Originally Posted by khaos974

An objective and undeniable reason as to why the sound of headphones changes over the 1st month?

As one wears a pair on new headphones, the foam (or any other material) inside the pads usual become softer and more compressible, as a result, after some time of use the drivers of the headphones come closer you your ear. Would it be  enough to change the reflections on the soundwaves on your ear and thus change the sound of one's headphones?

Yes, the positioning of headphones has a very large impact on how they sound, in just the way you've described. This is perhaps the only proven method by which large changes in headphones occur over reasonable periods of time. It's one of the reasons why any comparison of new versus old headphones may show differences, as this variable has never been controlled in any comparison I've seen.

Steve Guttenberg just published an article on his Cnet Audiophiliac blog today called, "Headphone 'burn-in': Fact or fantasy?", complete with a reference to Tyll's objective Inner Fidelity measurements of a K701 supposedly changing its sound over time. Conclusion: inconclusive. Comments?

Edited by grokit - 5/10/11 at 10:41pm

More or less it just seems to paraphrase Tyll's article.

Tyll himself states:

Quote:
Thanks for the mention, Steve.

As far as I'm concerned, the jury is still out as to whether there is a measurable break-in effect. Readers at InnerFidelity surmise some of the changes in my data may simply be from the headphone cushions "settling in" and moving slightly during the course of measurement. I'm currently running further tests on an already burned-in pair. I'll spill the beans here briefly: current test show this might be the case. I will be continuing to investigate. Further details will appear at InnerFidelity in coming weeks.

Suffice it to say, if there are measurable effects of headphone break-in, they are very, VERY small.

I have subjectively experienced break-in with the AKG K 701, and I do think I hear things change over time. I also think the greatest changes are psychological, however.

There ... that settles that, eh? :P

I do believe that pads may be the biggest source of change - but I'd also like to see measurements after the headphones haven't been playing for some hours (to cool down the coil/diaphragm).

That seems reasonable, hopefully that will come in the next round as it seems that Tyl will continue this line of research. It also seems like this could be yet another circular argument in the SS forum but I can definitely appreciate the John Grado quote, when he says that "All mechanical things need break-in." I've always thought that burn-in is a combination of the equipment breaking in, as well as our eardrums and brains adjusting their HRTF; I suppose this is the "psychological" part that Tyl is referring to but I think that it's physiological as well.

Edited by grokit - 5/11/11 at 2:44pm

Tyll and I are going to do some double blind testing to see if we can identify which 701 is "burned it" and which is not.  I am also going to suggest we try to make one headphone look like the other sonically by moving the ear cups around the dummy head, adjusting clamping tension, etc.  If we can make one graph look like the other this would suggest that we did not measure burn in.  If no matter what we do we cannot replicate the result other than using the burned in headphone, then this would suggest the possibility we measured the process.

Great stuff NA Blur! Looking forward to the results.

The family are away so I have been using my K702s for the first time in months and they do appear to have burned in again. They sounded shrill and brittle compared to the K271s but now have deepened and the bass appears fuller.

I think that there is evidence that small audible differences do occur with some headphones. It is not conclusive, so it may be my hearing or a combination of both.

it can be the dried out ear pads recovering

the increased weight explains the base response changing too you know

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