Originally Posted by kludgeaudio ➡️

This is kind of true but it is irrelevant to the operation of the speaker in the room. What determines how much air volume can get pushed out is actually the size of the cone multiplied by how far the cone can travel. So there are some fancy drivers out there that have a very long xmax and can move a lot of air from a small driver (those have other disadvantages although plenty of them are in use).

BUT.... to make this even more messy... that limits the total -level- that you can produce and not the low frequency corner. You can still build a speaker with small drivers that has a lot of low end extension... it just won't be able to be very loud without overloading. This isn't very common since most manufacturers want to sell speakers with plenty of headroom, but we do it for speakers intended for microphone testing, for instance.
--scott