When you are designing and building your home theater, and you want to go beyond just a basic room, you will need to take your room modes into consideration. Room modes (at a high level) are frequencies that reflect between parallel surfaces, and the low frequencies tend to be the ones that cause the trouble in your home theater. You can learn more about Room Modes here.
There are several different calculators out there, but the one that we use here, is ModeCalc, created by Ethan Winer and available from his site: RealTraps. Ethan also includes a nice Help section built into his calculator, so you will easily be able to use this for your room.
Using a calculator like this allows you to enter the dimensions of your room, and then the calculator will generate the modes of the room. Knowing the room modes will then allow you to design your acoustics plan, or even adjust a dimension (if you have the ability to move a wall/ceiling in your room).
From another article, you know that building a room that is a perfect cube (See Home Theater Dimensions) is not a good plan, and the reason is Room Modes. That cube will mean that you have the same frequency resonating in all three dimensions, so when anything is played at that frequency, it will sound like it has been amplified and “lengthened” compared to all other sounds.
So go download the calculator, and use the results to bring your home theater’s acoustic performance up to the next level.