Mainly the bass. It sounded very flabby and boomy. Overall sound is grainy. This is open box and using my iPhone. Right now I have them plugged into the Geek Pulse for burn in and it sounds better. I'm comparing it against the ED8 and the SE is brighter, clearer, forward vocals. I'm guessing bass will improve on both but the SE's bass isn't so bad now comparing it to the ED8. Still not complaining at the price paid for either.