Dan Clark Stealth's Pressure Relief Hole

[oberon]

I bought these Dan Clark Stealth headphones about two years ago and have been incredibly happy using them. I have to say, they're the best audio product I've ever purchased.
Recently, I've noticed that when I plug the pressure relief holes on the headphones, the sound image becomes solid, without the "silent" sound that Chinese users complained about before, and the listening experience is even more satisfying. If you have these headphones, you can give them a try.
I have a few theories. One is that this may be related to the clamping force, but I later plugged the hole with plasticine, and the sound image remains solid. Another hypothesis is that they've changed the back chamber structure of the headphones, perhaps altering the frequency response and the "reverberation," but I don't have a viable tool to verify this.

 

[oratory1990]

You'd mainly expect a difference in the bass - an opening in the back volume of the loudspeaker reduces the system's stiffness at low frequencies (the transition frequency is determined by the size of the back volume, and the length and diameter of the opening. Together they form a Helmholtz resonator)