This app tackles the problem by testing your own hearing using the devices as you would use them and compensates accordingly (so it takes into account how your own ears are hearing with a specific device). It is also useful to test your ears individually to see how they differ (pity the app does not do the ears individually to also compensate with differences between each ear.
In the attached image the app shows the difference for settings between my left and right ear (I use one earbud at a time to listen to podcasts).
See https://play.google.com/store/apps/details?id=eu.javeo.android.neutralizer
