Evidence of Headphone Break-In? Page 3

Ed. Note: This page has been edited. Original page had improper scale on THD data.)

Total Harmonic Distortion + noise Differences
Let's look at differences in Total Harmonic distortion. These are differences over time in %THD+noise at the 100dB setting.


Fig. 11 shows the difference over time for the left channel THD+noise at 100dB vs. frequency.


Fig. 12 shows the difference over time for the right channel THD+noise at 100dB vs. frequency.

Some expanded views:
(Note: glitch on THD curve at 205Hz is measurement artifact.)


Fig. 13 shows the difference over time for the left channel THD+noise at 100dB compared to the frequency response differences between 10Hz and 250Hz.


Fig. 14 shows the difference over time for the right channel THD+noise at 100dB compared to the frequency response differences between 10Hz and 250Hz.

There appears to be a strong relationship between the FR and THD data around the primary driver resonances centered around 80Hz-85Hz. Again, if there is evedence of break-in, this is probably it.

Notice the features between 35Hz and 50Hz on the THD curves. Total guess here, but at this low frequency we might be seeing the diaphragm material breaking-in and changing its resistance to bending at the excursion extremes. No change in the FR data to go along with it though.

Now note the feature at around 185Hz on both THD charts. This look like it may be something happening at the second harmonic of the primary driver resonance. There are very small changes in the FR data at these points, but they're small and difficult to identify as related.

Now for a look at the squirrely stuff between 1kHz and 2kHz.


Fig. 15 shows the difference over time for the left channel THD+noise at 100dB compared to the frequency response differences between 400Hz and 3000Hz.


Fig. 16 shows the difference over time for the right channel THD+noise at 100dB compared to the frequency response differences between 400Hz and 3000Hz.

Here I see little correlation between FR and THD data, other than the 20 hour curve does seem to be the odd man out.

I also measured the difference in impedance


Fig. 15 shows the difference over time for the left channel impedance.

Here you can see the generally moving trend with time, and the exception of the data set at the 20 hour mark (light blue).

Summary Did I show break-in exists? No. There are too many variables still. Was it simply movement? I don't know. If I did it again to another brand new pair would I get the same results? I don't know. If I did it to an already broken in pair would I get the same results? I don't know.

What I do know is that during the course of these measurements some things changed. While the data showed only very small differences, the data was clearly above the noise, and a general trend observable. The data also showed a discontinuity around the 20 hour mark in both the FR and THD data. While, it seems to me, much of the change observed could easily be due to movement, especially in the frequencies above 5kHz, some changes seem more likely due to break-in. In particular, the changes in frequency response around the fundamental resonance of the driver at 80Hz, and in %THD+noise at the same frequency and at around 40Hz.

There were also things I have no idea about: the changes in FR and THD at around 1100Hz seems quite confused; the THD wiggle at 180Hz may be a second harmonic mode of the primary driver resonance, but there's little in the FR data to support anything.

The full measurement spreadsheets for the entire test is here.

Alrighty then, time for some fun, let's give away a pair of broken-in Quincy Jones Q701s. Within the next month or two, I will be willing to set the chamber and test system aside again for another four day experiment. Between now and the time I publish the next article, I will be reading the comments here. The comment I find most enjoyable (could be technical ... could just be funny) will win a Q701.

Have fun!

ARTICLE CONTENTS
Share | |

X
Enter your InnerFidelity username.
Enter the password that accompanies your username.
Loading