I assume this has something to do with impedance. Again, however, I cannot find this key information in Nexus 4's specification or the Google Play Store headset's. This can also be compatibility or software issue. But I read somewhere on the internet that unfortunately the mic volume and the earphone volume are not separately adjustable on Nexus 4. If that's not the case, please give me a guide as to how to do it. I am running factory 4.4 rom, rooted and GravityBox installed. If it has something to do with compatibility and/or impedance, please recommend a model (with mic) that works best with Nexus 4 which is not plugin when it comes to earphones. In terms of sound quality, I am not picky. To me, the iPhone headset isn't bad in sound quality. And I'd be totally satisfied if the sound quality is at the same level or close to a Sennheiser MX500.