Chris Whealy wrote:

The church I go to recently looked into getting a vertical line array
system, but it rapidly became apparent that our auditorium was too
small for such a speaker system.

That would be an economic choice, not a technical choice. Line arrays can be
made to work well in smaller rooms, but of course the line array would then
itself be smaller.

In order to be in the far field, the
audience should not be closer that 25 to 30 metres from the line
array.

Actually, there are problems with being too close to a line array of a given
size, but the problem can be solved by using a smaller array.

Our audience is only 15m away. Also, you need a fairly
large vertical height in which to hang the array, again, our building
could not accomodate such a system.

Again, the geometry of line arrays is scalable.

As great as they are, unless your building is acousically large, it
does not make much sense to use a line array. Alternatively, line
arrays are excellent for outdoor events.

I've seen line arrays used to great advantage indoors. I've sat reasonably
close to them when they were operating and they remained highly effective.

There are useful things that can be done with arrays and AFAIK only with
arrays - these people were early pioneers:

http://www.duran-audio.com/Products/Intellivox.htm

Here in the UK, I went to a "son et lumiere" style evening at Audley
End House last summer, where there was a symphony orchestra and
fireworks. There must have been 15,000 people there that evening and
on either side of the stage was a line array column. The sound from
quality was fantastic, with very little SPL variation over the entire
audience depth (about 500m).

Arrays can provide similar benefits in smaller spaces.

Take a look at http://www.l-acoustics.com/pdfproda/wavefront.zip for
more details on the theory behind line arrays.

Other sources:

http://www.meyersound.com/support/papers/steering/

http://www.eaw.com/products/DSA/

http://www.audiosystems.ch/live/jbl/...r_englisch.pdf