What channels are heard in a comercial theater??

The side arrays are playing the left rear and right rear tracks. IMAX soundtracks are 6 channels full range. No processor is used. The sixth channel is for a top screen speaker. This channel is unused in a DMR IMAX movie like The Dark Knight. The Sub bass track is summed from all 6 tracks 80Hz and down. It is possible that the theater you went to has some sort of processor between the IMAX feed and the side arrays. IMAX is retro fitting their systems into cineplexes. There will be variances between any two. If there is a speaker array on the back wall it is likely summed from the LR and RR tracks.

Assuming the movie soundtrack has only 5 channels, do those speakers on the side play information from the front channels or rear channels?

Side channels but they will probably do tricks with frequency response and phasing to make sure the sound field has broad consistent feel for listeners sitting in a variety of positions.

I'm not sure. It's either as other said, all the side channels playing at same time on sides, and/or matrix'd rears in a 6.1 track. Or, it could be some matrix of fronts spread to sides, but doubt it. I'd have to look into it, and any differences in IMAX vs. standard. My presumption is that the Steuspeed's position is mostly right. However, in the IMAX that I've been to, all the channels where "active" full range channels, with separate LFE, I believe. Could have been crossed over to 80hz from all channels, but not sure. Lol! I guess it could be anything really. I'm just presuming.
Yep, I will look into it, cause I want to know myself.
Perhaps with a few calls and some footwork, someone here can get to the bottom of the matter, and know exactly what's being steered where and processed how in these systems. I'm out of the loop myself, presently.

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Steuspeed....so, if a guy is sitting in row 7, he probably has three or four pairs of speakers on the side walls in front of him that's playing rear channel tracks. Amazing, because I could not localize where the info was coming from....just total imersion. In my home theater my seat is 30 feet from the screen and I am cosidering another pair of speakers about ten feet in front of me along the side walls for more room fill....and I was wondering what channel to assign to those speakers. I have extra sets of speakers and amps to give this a try.

My 5.1 config as of now I have:

1 sub

....all speakers below are full range
1 center
2 fronts L&R floor standing to the side of the screen.
2 front side axis L&R : (along the side wall eight feet in front of the main front speakers, mounted on the wall 5 ft off the floor...Y-connected from front channel.
2 surrounds mounted 10 ft off the floor on side walls 5 ft behind seating.

Proposed:

2 surrounds L&R 10 ft in front of seating, mounted 5 ft off the floor, Y-connected from surround channels.

...to make it a true 7.1 config...

2 surround back L&R 20 feet behind seating, mounted 10 ft above seating area, centered 10 feet apart. I have to re-read my manual to see if the rear surrounds in a 7.1 config are engaged on 5.1 material.

My system sounds really good as-is....I'm just trying to see if I can get better.

The Dark Knight in IMAX started all of this insanity.

To all of you, Steuspeed, Naked and Shadorne...thank you for your input, I really appreciate it....again, Audiogon has been a godsend for me in helping me put together my 2-channel and home theater systems.

...thanks again....mitch
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Mitch,

It looks like your processor has L&R surround outputs and LR & RR surround outputs. I would scrap those front side axis speakers. They don't seem to be in your photos? Anyway, hook up your side speakers to the surround outputs. Add the rear wall speakers and use the LR & RR outputs for those. Sounds like you have the positioning about right 2-3 feet above your head at the seated position. A few more in the back will be ok. Might tilt them down a bit. I see your bass speakers way back from the L & R. They should be in the same plane as the L & R for proper phase. You need to move those forward. That center speaker on the floor is bad bad bad. You need to get it up 2 or 3 feet. Try turning it on its side like I told you before. Hey, free experiment. I would also try pulling the L&R speaker sets forward about 1.5 foot in front of the screen and set your distance for the front speakers all at zero. Recalibrate your pink noise levels at the seated position. One other experiment to try is set the bass units together right behind the center speaker. IMAX discovered that multiple subs cancel out each other in large spaces. An IMAX sub bass has 8 18" drivers mounted in a slot . Imagine a doorless coat closet with 4 opposing drivers mounted on each side wall firing at each other. The 8 pistons push the air out the closet door in one acoustic wave front right at the audience. Your room could use some acoustic treatment. I am not sure where to start with that though. Tough room.