Michael,
Keep in mind that the electronic slope will combine with the acoustical slope. Depending on how wide your baffle is, the Betsy will be rolling off somewhere on it's own. The Alpha could be doing any number of things. I'm aiming for a second order crossover at about 165 hz. To accomplish that, I have a first order crossover (single cap) on the Betsys (at line level) at right about that point (in combination with the baffle width), but on the woofers, I'm using the miniDSP with a 2nd order slope set much lower (maybe 80hz?), due to their rising response.
It really sounds like it isn't working for you, so there are three ways to approach it.
One is to measure. You can measure the system in whole and the drivers individually, both with and without the crossover. That'll give you an idea of what's happening. Of course, measuring is hard to get right, and you can misinform yourself that way too!
Second would be to run some models of the drivers on the baffle and see what it looks like. There are various software solutions, and I'm probably out-of-touch as to what the best free solutions are.
Third would be to experiment and see what happens. Try different slopes and crossover points. It does help to think about what you are doing a bit, especially regarding the fullrangers. You can end up working them too hard electrically to make up for acoustical problems. So, before you do any crazy EQing on them, I'd run through a bunch of different options on the woofers.
I did sort of a combination of 2 and 3, first looking at some simulations to see what was most likely happening, then playing with the miniDSP until it seemed to work out.
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
) I'm back. Well a couple of weeks ago I bought a pair of betsys and this weekend I was finally able to put them to use. 
