Source: What To Be Aware Of When Using Headphones For Mixing : Ask.Audio
This has been my problem from time to time:
“And once again, while the perception of bass in the mix may vary from room to room, the perception of bass may also vary from phones to speakers. Without the feeling of the bass vibrations in the room and the listener’s body – absent in headphone monitoring, even with phones that have good bass extension – there may be a tendency to overdo low end EQ if mixing in phones, which can then sound muddy or boomy over speaker playback.”