Headphones

Hello everyone, During the black Friday I bought the Fidelio X2HR. I read online that, before using new headphones, you have to do a "burn-in" for several hours. I connected the Fidelio to my DAC/AMP (a Fiio K9) and I left them there for several hours while a mix of music and pink noise was playing. However, since I'm used to my old 150 ohm headphones (superlux hd681 evo), I putted the volume almost at max level (low gain), to be precise the knob was a little over the 3 o'clock position. Now I'm using my new Fidelio but the details, the clarity and especially the highs seem worse than my old headphones, but maybe it's just my perception I can't tell for sure. I noticed that my Fidelio sounds better at lower volumes, the bass don't overshadow other instruments, however I still get the impression that they don't sound as good as my old ones. Will the sound of the Fidelio improve over time?is it just my impression and I just have to get use to the new headphones? Or should I return the Fidelio back?