How does eq make it better than it was intended? Physical limitations? Why do you have insufficient bass and peaky treble? Not that there’s anything wrong with that.
If you look into head phone and speaker design there is a trade off for everything. So it really depends on the manufactures goals of what they're trying to accomplish. These are the physical limitations. EQ makes up for these physical limitations. Only manufacture that seems to got around this is DCA, by using their AMTS system. You would have insufficient bass and peaky treble depending on the totality of the design and FR.