You haven't heard a great large Apogee sound until you hear a properly driven one in a large room. I would think that applies to all large dipoles.
Why should some speakers need a big room?
It's often said that some speakers need a big room to perform well. Couldn't you just turn down the volume? And if the speakers don't sound nice at low levels, isn't this a fault with the speakers?
(And I never heard any say a pair of headphones needed a big head...)
(And I never heard any say a pair of headphones needed a big head...)