I've gone and read the JBL reference. I'm getting a bit lost in terminology. Am I using the the phrase correctly if when I say a speaker is directive I mean that the off-axis response is poor? The JBL paper seems to use it to mean the opposite. Also what do 'directivity factor' and DI mean? They are the labels on the vertical axis of graph 1B.

Graph 4B seems to show horizontal lobing. Is this a separate effect than the vertical comb filtering you describe in your whitepaper?

-Josh