Anyone running 9 or 10 speakers in their HT setup?

I run a IMAX theater so I can tell you exactly what they are doing. It sounds like you were in a smaller joint venture theater (Regal or AMC), because a traditional stand alone IMAX does not use multiple arrays of speakers. Typically they use 6 Full range speakers that are IDENTICAL and ONE huge subwoofer dead center screen. Mine has 8 18" drivers and you can walk inside it. IMAX found that multiple subwoofers actually cancel each other out. The six speaker locations are L-C-R LR RR and Top Screen. Top screen is rarely used. It works well for rocket launches. Some movies have no top screen content at all. The source is is either 6 channel 35mm analog mag tape or 6 channel digital files. All tracks are full range, and there is NO processor. The sub bass track is summed off all 6 channels. All amps are also IDENTICAL except for wattage. Older theaters use modified Bryston amps. All drivers have electronic crossovers. Each 4 way speaker is quad amped. The new theaters are using class D amps. I can't recall the make. I think they sound more digital though. The speakers are custom designed, but they use Electro Voice and JBL drivers. To me they sound like big boxes with horns. Dynamic, you bet. Hi-fi, not so much.

So basically they have been doing a variation of 5.1 for 40 years now. I doubt all those speaker arrays were running for Batman. Those arrays came with Dolby surround. I could be wrong. Not all theaters have the sound system supplied by IMAX. That is an additional cost.

If you add side or rear channels it will make your surround more seamless. Matching amps and speakers are key. Proper speaker placement, acoustic treatment and set-up will make your system sing. I see these basic concepts ignored over and over by pros and joes.

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I LOVE THIS FORUM!!

Thank you Steuspeed! Invaluable info. Yes it was at a joint venture theater. The full sized IMAX theater here in Los Angeles is at the Univ of Southern Calif Museum of Science and Industry. I've never heard of them showing a comercial film there....I've seen several nature-type doucmentaries there over the years. Nothing in those documentaries to challenge the sound system like the Batman soundtrack though.
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You need to see Batman at the REAL IMAX. Multiple scenes are shot in real IMAX and will fill the entires IMAX screen. This is a first for a Hollywood style film. I would be interested in your feedback between the two venues.

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The IMAX screen I saw was six stories high. You could tell when the IMAX shots were on the screen.....the on-screen image filled the entire screen. The 35 mm portions of the movie of course were letterbox style, still outstanding though. Even though the aspect ratios changed periodically during the movie...it was done seamlessly. My buddy didn't even notice that the aspect ratios went back and forth.
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How much bigger is the screen at a real IMAX theater?

That sounds like a big retrofit. Some JV theaters don't have that kind of ceiling height. You would have to go on-line and check screen dimensions. The Boeing IMAX in Seattle is 62' x 82', so you may have seen all there is to see. I have 79' dome. We are not running Hollywood movies.