I used to use my iPad to stream music to my Kanto Yumi wireless speakers and my headphones. One day, I noticed the music felt...off. I couldn't put my finger on it, but it was lifeless, dull and flat. I checked to see if I accidentally turned on Apple's EQ settings, but it was disabled.
I thought it was the speakers, so I reset everything back to factory settings. Then I listened over EarPods and Dirac HD Player, and it was also dull.
Finally, after a month of this, I dug through the iPad's menus. I had inadvertently turned music playback to mono! So I'm satisfied with leaving my setup alone, lest I ruin it with tweaking.