Michael,

It isn't particularly useful to the consumer, and even for an engineer
this information has little to do with the perceived performance of a
loudspeaker.

I would dispute that off-axis response is unimportant, and Arny gave some
good reasons. But here's my real motive for wanting to have a better idea of
what most speakers really do:

A lot of audiophiles treat their entire front wall with thin absorption,
like 1-inch 703 rigid fiberglass, because they are told that loudspeakers
radiate mids and highs out the rear so that's another point of first
reflections. I know intuitively, and by listening, that lows are much more
omnidirectional than mids and highs. But in order to determine how much
thickness is needed on the front wall - or if any absorption is even needed
there at all - I need to know at what frequency most speakers "cross over"
from sending out the front to radiating omnidirectionally. I don't even care
about the specific lobing patterns at higher frequencies, so much as the
frequency at which a basic change in directionality occurs.

I would test this myself but it's a huge pain in the butt to run a bunch of
really long wires outside, borrow a tall ladder to place a speaker on, put a
microphone on a long pole, and so forth. I mean, someone somewhere must have
already done this properly in an anechoic chamber!

--Ethan