Bob is correct in his assessment of the 722 over an 18. A single 722 over a sub lacks in the often overlooked but very important range of 90 to 300 Htz. I have found when using two 722's per side, the lower mids couple nicely and the problem is solved. The 70 degree horns splay nicely together and provide wide, even coverage for outdoor gigs.
Bottom line, if you are using one per side, the 725, or new 825 would be a choice I think you would be happy with.