Speaker placement for 2-ch AND 5-ch same room


I am building a dedicated room for my gear. I have reasonable architectural freedom, but not unlimited space. Right now we're looking at 15 x 21 x 9 or thereabouts.

I have suddenly realized that I have enough equipment to install two separate systems, one for 5-ch and one for 2-ch. I'm looking for advise as to how to position the speakers. The 2-ch mains are MartinLogan Odysseys; if we go with two systems, the 5-ch mains would be ML Scenarios with Cinema center. The screen is retractable and automated, so I could have the screen drop in front of the Odysseys and place the Scenarios outside of them and slightly in front. I think that putting the big Odysseys outside the Scenarios would start to put them too close to the sides of the room (screen is 92" diag = 7' 6" wide plus tensioning).

My priorities is 2-channel, but I got WAF by making the 5-ch movies work well.

Any other suggestions? Am I nuts?
blw
Haven't been to Rives' site yet (travelling this week, really busy) but I'll do that. Dropping the ceiling 3" would be no problem whatever - we'll just dig 3" less.

Where is there reading material about this? I know about the stuff at Cardas and the much more general stuff by Robert Harley. I'll definitely dig into the room sizing thing.

Anything else on speaker placement of those five front speakers (2 L, 2R, 1C)?
Try the book Sound Studio Construction on a Budget by F. Alton Everest. Good stuff. BTW, don't drop your ceiling yet, I was talking in generalities. I'll be happy to send you a spreadsheet on these calculations so you can test different dimensional impacts. Let me know if you are spreadsheet savvy and I'll work on it over the weekend to make it a bit less subjective and easier to use. Cheers.
If you're really looking for world class performance from your system, as you're obviously ready to plunk down sizeable cash for your gear(which is not even half the battle really), may I highly suggest having a professinal work all that out for you!!! There's simply far too many variables to consider, and too many factors that are involved in achieving a perfect balance between flat/even frequency response and the best anchor spots for all the speakers, from all the pertinent seating possitions. There's another long long list of variables to consider if one wishes to "do it right" as well...but that's getting off track here.
A quick answer for you is that you might try going back through all the past Stereophile Guide to Home Theater mags for the past 3 years or so, and find Russ Herschelmann's "Home Theater Architect" on going article, and read all of em!!! Other recommended reading is the stand-by, F. Alton Everest's "Master Handbook of Acoustics"
Also, you could check any other HT and Audio Mag for back articles on acoustics, room set up, bass vs. Space, speaker/seating suggestions, etc.
Anyway, I personally would need to see more of the particual room to make some more "hard" suggestions, calculations, and recommendations myself. Also, how flexible you are with seating and/speaker locations and layout will make a huge differnce as to the potential of the project, and what kind, if any, of a level of "EQ'ing would be needed for the HT system(yes, the dreadded Audiophile "bad word"...EQ).
This all may or may not be as much as you want to hear from your inquirey, but it's the truth.
Yes, you're on the right track with getting assistance to proper speaker(and seating) location for best sound, but it's just not that simple, to say "put them there or there, etc"...that from years of experience of doing 100's even 1000+ set-up's! There's a lot of fine tunning, trial and error, and knowledge that goes along with getting world class sonics out of any room/system!...make no mistake about it.
Anyway quick answers to your question really It isn't that simple to be true.
People Like R. Rives @ Rivesaudio.com have a website you can check out for some consulting ref's...might check them out. Also, if you're looking for a cheaper route than "Consultants", may I suggest attending one of Russ Herschelmann's anual seminars in San Francisco! Russ is probably the premier custom theater deisgner/acoustical engineer/consultant in the biz today, has worked on the largest jobs(including the I-Max at Disney World), and writes for Stereophile GHT, HT Mag, and AV Interiors on acoutics and HT related...definetly worth the $1000 or so to attend his work shop!
So be informed however, that simply reading it all won't replace experience, which you cannot expect to replace with some "head Knowledge"...cause there's no replacemnt for years of tried and true eperience and skill!

P.S., give some more details of your room/structure/possible obstacles and I can give some more solid suggestions

Chilidog91311@yahoo.com