First home theater room - Advice on room dimensions

Discussion in 'Archived Threads 2001-2004' started by Chris S, Jan 31, 2002.

  1. Chris S

    Chris S Cinematographer

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    My wife and I have finally found a home and it looks like there will be an extra room which I have been given permission [​IMG] to turn into a home theater. The room is 10' x 13' with a vaulted ceiling that is about 11-12 feet high. I was wondering what your thoughts where on these dimensions. I thought they sounded pretty good, not optimal but pretty good. My other alternative is a room that is 11x10, but from what I understand that room would generate to many "null" points(?). Later tonight I will post some diagrams of the room to show the actual layout of the closet, doors, and window.
    O'yea I will be using a 41 inch widescreen RPTV in the room with floor standing Paradigm speakers. If you need a more information on my gear check out my website for the complete list.
    Chris S.
     
  2. Chris S

    Chris S Cinematographer

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    Okay here are a couple cut aways from what the room looks like. The first image is how I think I would probably layout the room. The second is just a profile to show the shape of the vaulted ceiling.
    [​IMG]
    [​IMG]
    I suppose my next concern would probably be acoustics since the only absorbing materials in the room will be a curtain and the couch. Is anyone using acoustic panels? Does it really improve the sound of the room by a great deal? Any other suggestions are greatly appreciated.
    Thanks,
    Chris S.
     
  3. Eric Huffstutler

    Eric Huffstutler Screenwriter

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    I too am interested in finding out the answer to your question but do know that DOLBY suggests that the room be twice as long as wide to get the optimal surround effect.

    Anyone... what would be the minimal lenght x width ratio to achive proper surround sound without null or crossover points?
     
  4. Chad Anson

    Chad Anson Second Unit

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  5. Chris S

    Chris S Cinematographer

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    Well after reading just about every article I could find I think that I have come to only one conclusion. As long as you don't have a perfectly square room (width, length, and height) you should be okay. I found a lot of contradictory opinions about the perfect room size, but everyone agreed that a prefect square was definitely not a favorable configuration.
    However if one does have a room like this there are a lot of things that can be done to break up the walls so that they aren't exactly so parallel and so square. The one I liked the most was to add thin columns to the surrounding walls. When done well it can really make the room look nice. Here is an example of one of the nicest that I have seen. I suppose if they are insulated properly they will probably work really well as acoustic panels.
    Chris S.
     
  6. Chad Anson

    Chad Anson Second Unit

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    Chris,

    I agree with your conclusion. It's also a view shared by Dennis Erskine, a very highly regarded home theater designer that frequents avsforum.com. One thing to keep in mind about columns, build the room (including drywall, etc.) and then add the columns.
     
  7. Jacques C

    Jacques C Stunt Coordinator

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    Chris,

    I threw your room and speaker layout into a modeling program quick, and surprisingly the sloped ceiling does a pretty good job of breaking up room modes. You have a slight null at 30Hz and another at ~75Hz. The one at 75Hz is worse and is probably 10dB or so. Not bad at all.

    Not sure from what you said how "live" your room is.

    I don't have web space to post the images but I will email them to you.

    Jacques
     
  8. Chris S

    Chris S Cinematographer

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    Wow Jacques thank you! These images are great. For everyone else who is intereted I have placed them on my server. They are:
    30Hz-3D
    30Hz-contour
    75Hz-contour
    I've never used one of these programs before so if you could provide a short explanation as to what we're looking at here it would be great. Thanks again for the charts [​IMG]
    Chris S.
     
  9. Jacques C

    Jacques C Stunt Coordinator

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    Hey Chris,
    That is the output from a program I picked up a couple weeks ago called CARA (check it out at www.rhintek.com). What you see in the three charts (one is 3D, the other two are essentially top-don filled contour plots) are the frequency response of the room with the room and speaker layout given as in Chris' diagram. The slice looked at is at constant height 3 ft off the floor - the approximate listening height for a seated person.
    "L1" is the location of the listener in the simulation.
    As it turned out 30 and 75 Hz are the worst spots for bass nulls at that spot. The program calculates from 5-20000 Hz, but it is impossible to export all of that data. The room response isn't too bad, though. All rooms will have nulls to one degree or another - those are less than the room I am designing. ;-)
    If interested, the program is designed to:
    1. Predict for how "live" your room is depending on the materials used. You can define your own material types, if needed.
    2. Optimize speaker locations. You can create custom profiles for your own speakers (it has some already).
    3. Solve the room for frequency response at listening level, time response, and a few other things. Can handle odd room shapes - octagonal, L-shaped, etc.
    Considering I am in the planning stages of building an HT room, this was $50 well spent. If there is one disadvantage to the program, it is *very* computation intensive. As you increase the maximum reflection order the computation times go up exponentially - for that room a 4th order would take ~10 minutes, 5th order 10 hours, 6th order 2 days, etc. That was a 4th order run.
    Its a fun toy. ;-) It has given me some peace of mind with the room I am designing. I think for odd shaped rooms it becomes a godsend when trying to figure out acoustics - I haven't heard of anything else that can handle odd room shapes.
    Take care.
    Jacques
     

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