Hi! The main difference between Eminence 15:s that concerns open baffle builders is the Qts value, which is suitably high on the alpha 15. That's why it is popular here.
Beta, gamma and delta models have lower Qts values, so they will need more compensation, by equalising or filtering, to not drop off too early (too lean bass).
Dunno if this was my first post - in that case, hi! I have been coming here now and then for a year or two, but haven't had anything to post about really. Want to build two pairs of OBs for the house, but there is always something else that happens...