Technically it is possible to tune any given driver to almost any range, but in reality most of the really goofy variations come down to being what I call 'engineering stunts'. The reason is simply that although it may produce a clear tne at a low frequency a typical smaller driver cannot generate a useful quantity of output at the low frequency extreme and so the design will be impractical.

So in practice you see low frequency extension typically (roughly) follows the radiating area of the low frequency drivers. Some bass systems DO use multiple smaller drivers to good effect, though.