Most woofers have rising response, and this tends to act in a complementary fashion to the falling response of the horn, unless there is a low-pass filter in the system. A low-pass filter can take the form of an electronic crossover or it can be an acoustic filter made by horn folds that reflect midrange energies within the horn instead of directing them towards the mouth. If you plan to crossover at 100Hz, this is of little importance. But if you want the option of higher-frequency output, then wave path and reflector geometries become significant.