Surround placement in a very large room (1 Viewer)

[Daniel J]

I am setting up a 6 channel sound system in a 80'(screen-back) x 33' Wide x 20' high room. Speakers will be flown from the ceiling.
What is the best position for my surround speakers? All the manuals I've read suggest side placement facing inward, does that carry over into a room of this size, or should I be trying some other positions?
Are there any books/websites that would help me?

 

[GaryM]

IMHO, it depends upon what you are doing in this large room.
In a typical smaller "Home Theater" room, there are a few seats and the audio "sweet spot" where you get perfect surround sound is a rather small area - and two surround speakers are sufficient. You could do something like this in the larger space, centering listener seating with the five speakers equi-distant from the seating, more or less in a circle, with the front speakers aimed directly at the listening area, and the two surround speakers aimed above ear level. Since you are suspending speakers, you would mount the RF, CF, and LF speakers above the screen in the top right corner, the center top, and the top left corner of the screen - this ties the dialogue to the screen.
If however, the idea behind the large room is to use a large venue projector, a very large screen, and multiple rows of seating, then a different approach is called for, one more similar to a commercial movie theater. In such a space you want to make the audio "sweet spot" as large as possible. The best way to do so is to use multiple surround speakers - I would suggest 4 identical surround speakers per side, mounted up high and aimed "off-axis" above the listener's ears. The 4 speakers can be connected in "Series/Parallel" fashion to each surround channel, and will represent the same load impedance as a single speaker.
There are other audio considerations in a large space, such as control of reverberation. Allow me to suggest that for such an installation, you either seek professional assistance, or study the acoustic techniques involved yourself before finishing plans for your theater.
You can start reading at the Dolby Laboratories site below:
http://www.dolby.com/ht/
Gary