need help designing a crossover for delta12LF and alpha8MR

[Guja]

I'm building a budget cab with 2xdelta12lf, one alpha8mr and a tweeter. Any sugestions how should it be crossed? Guess somewhere around 700-800 hz would be ok, and their sensitivities match, but how exactly, what types and what slopes would perform best?
Is it good to use low pass on midrange, or not, and what slope..
..also, is there any (cheap) tweeter with good dispersion pattern, and how should a crossover for it look like?
thx..

[Guja]

is it ok to use a crossover from fearfull designed for two twelves and 18sound midrange (called cheap but effective crossover)?

[billfitzmaurice]

Loudspeaker Design Software

Be forewarned that compared to crossovers designing a cab is child's play.