Most of the line array stuff is pure hype. When discussing this issue recently, a friend of mine put it well when he said: "People seldom need the power density that a line array can provide, and almost never have a seating area that is the right shape to be covered by a line array. And you can't just stick a pair of them side by side to widen the coverage. Most projects can't fit a tall enough line array to have a broadband line array behaviour, so in the frequency range it would really help (80-250Hz) most of the line arrays used aren't line arrays at all."
Referring to the ad hype, he said:
"At least they generally haven't included the old Meyer B.S. that
promoted the idea that the sound could go out so far and then just drop off. Line arrays just keep going and going and going, except for excess atmospheric attenuation of course.
"I never hear that issue addressed when people claim 500'+ of coverage without significant level loss, maybe at 500Hz, but the 4khz will be sucked up by the air by the time you get that far away, and a good bit of 2khz too. The last time I actually used a line array it was a stack of 4x 203B/290's in a Giant Voice system. Even if you can get true line array behaviour and make the wavefront cylindrical rather than spherical, you can get the drop off in level down to -3dB/doubling of distance, but the excess atmospheric attentuation doesn't change, it's still something like -8dB/100ft @8kHz and -5dB/100ft @ 4kHz."
I think Barry McKinnon said it rather well...