It doesn't move much air like dynamic drivers.
Also, if anyone's interested, I don't have a preference for dynamic or BA, it entirely depends on the headphone. Having heard quite a few IEMs the EX600 and hf5 remains my favorites, both are fairly flat, yet they sound so different.
Impact is more a function of speed and focus than air volume alone which BA's have in spades. Plenty of BA's hit harder than either the HF5, ER4 or EX600 but not as general rule. If you move a lot of air slowly and unfocused, you will get little impact. F=M * A
Edited by Anaxilus - 1/12/12 at 7:32pm