Please be advised that the release of '''Android v5.0''' ('''Lollipop''') improved the Volume and clarity of the Nexus 5, somewhat. However, there is a more powerful improvement available, just follow the link (http://www.androidrootz.com/2013/12/volume-boost-sound-mod-for-nexus-5.html). For this to work, you will require Root Access and an Unlocked Bootloader.
When you test drive this with a good Headphone, it will BLOW your MIND, and your ear as well.
Dogg