Iphone 6 sound quality

Hey guys!

Right now im sitting with my iphone 6 with the latest version 8.4 and listening to some music in my bose qc15 headphones. The problem I started to notice some months ago is that the sound quality is poor while im using headset. But when I plug the headset in to my old iphone 5s the quality is much better. The sound is not as warm as either my macbook air or my old iphones and when I am listening to music such as house it sound even worse, especially during the drop. At first I thought is was something wrong with my phone but now when i just got my second iphone 6 I still have the same problem. I wonder if it's just how the iphone 6 sounds when listening through headphones or if there may be any settings I can change to make it sound better?

Thanks in advance!