Default [Q] HTC DX - Volume on Headphones too low? EU cap maybe?

Hey guys.

I bought a new HTC Desire X because I gave my old one to my sister. Everything works fine but when I play music, the Volume is too low and it gave me a warning too that I shouldnt listen too loud. When I put the Volume at the my new HTC DX on 100% its like 70% on the old one. I tested the same headphones (Sennheiser CX300), the same player and the same mp3 file. The old HTC is much louder.
SO does anyone know why this happens? Is there a way to solve.
My HTC Desire has Vodafon Branding (no vodafon intro though) and I bought in the EU.
So maybe someone knows a solution?