Earl has recently posted the fourth chapter of his forthcoming book online. Earl looks at measurements from the point of view of the loudspeaker designer, rather than that of the marketing department. Most real-world measurements that give genuinely useful information will probably never be seen by us because they look awful compared to the oversmoothed on-axis curves that have been our steady diet for years now. Earl examines many different measurement techniques and topics.
Of enormous interest to me was the information on polar response, directivity index, and power response. As you will see, Wayne has been barking up the right tree all along with his emphasis on matching up the directivity indices. He's taking an acoustic solution, which is worlds better than relying on equalization alone because equalization cannot fix problems that are fundamentally acoustic.
In particular, take a look at Figure 4-6 and Figure 4-10. The first shows two very similar-looking on-axis response curves. The second is the power response curves for the same two speakers. As you will see, the problems introduced by inattention to directivity issues are huge, way beyond what a bit of digital EQ can begin to address.
Enjoy!
Duke