Evidence of Headphone Break-In? Page 2

The Break-In Data
Let's first take a look at the full spectrum data from 10Hz to 22kHz for the left and the right channel.


Fig. 1 Show the left channel frequency response differences over 90 hours. If there were no differences from one measurement to the next, the result would be a straight line. With the exception of the large spike at about 12500Hz all changes between measurements lies between +/- 1dB. This is a fairly small amount of change across the board.


Fig. 2 shows the right channel frequency response differences. Please note a few things:

  • Both graphs have the data normalized to zero at 300Hz. This frequency was chosen because the data shows little difference between data-sets occur in this area.
  • Both graphs show the low frequencies slowly rising in amplitude.
  • Both graphs show the largest differences occur from roughly 5kHz and up.
  • Both graphs show erratic behavior around the fundamental driver resonance at about 80Hz, and at between 800Hz and 2000Hz.
  • You'll have to look very carefully (we'll take a closer look in a minute) but in both graphs something discontinuous happens at the 20 hour mark (light blue line).
Let's start with a closer look at the highs:


Fig. 3 Shows frequency response between 3000Hz and 20000Hz for the left channel.


Fig. 4 Shows frequency response between 3000Hz and 20000Hz for the right channel.

In figures 3 and 4 the changes in the high frequencies trend in one direction with the exception of the 20 and 40 hour mark. My tendency is to believe these data could easily indicate slow changes in position. The problem is the 20 and 40 hour data shows what would indicate movement in a reversed direction, and then the 65 hour mark goes back in the original direction. I would expect gravity or the spring tension in the headband to cause changes to all move in the same direction over time.

Let's look at the low end of the scale.
Fig. 5 shows a close up view of the left channel FR differences over time in the range between 20Hz and 300Hz.


Fig. 6 shows a close up view of the right channel FR differences over time in the range between 20Hz and 300Hz.

The gradual slightly increasing bass response could certainly be the seal of the headphone getting slowly better over time as the cushions seat against the head. However, at the 20 and 40 hour mark significant changes occur at about 80Hz; this is the fundamental driver resonance point. I don't think these data could me made by position change; at this frequency, FR changes due to position are from the changes of the seal and are not very frequency selective. These changes can really only be attributed to something happening with the driver during the 20-40 hour time period. I'd say this may be evidence of driver break-in.

Here's a closer look at this frequency response area:


Fig. 7 shows a close up view of the left channel FR differences over time in the range between 60Hz and 180Hz.


Fig. 8 shows a close up view of the right channel FR differences over time in the range between 60Hz and 180Hz.

Here again we see the 20 hour curve doing something odd. You'll also notice that in both channels, the curve at 20 hours is similar shape, but larger in amplitude than the 65 hour curve. Indicating to me that something happens to the drive at around this point that changes it's character and then it settles into a new norm.

And then there's this stuff up around 1000Hz.


Fig. 9 shows a close up view of the left channel FR differences over time in the range between 800Hz and 2000Hz.


Fig. 10 shows a close up view of the right channel FR differences over time in the range between 800Hz and 2000Hz.

Something very different about the 20 hour curve, that's for sure.

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