what crossover orders can be mixed/used together and what are the subjective outcomes

i want to use 500hz 1st order between evm15ls in 90 hz straight horns to le5's (in 300 hz edgarhorns) ...now the problem !....crossing to altec 806/811's ( at 5k 1st order) sounds harsh.

If i cross 2nd or 3rd order to the altec to roll it off more quickly what happens to phase with regard to the other drivers

don't really understand phase issues so have probably just made myself look foolish...oh well!

must i run the whole rig in 2nd or 3rd order if i am to protect the compression drivers?

cheers

gary

p.s my p.c can't seem to read the crossover document properly .pity i expect the answers are in there somewhere!