Typically a false wall is built within the structure of an existing room. Then the AT screen is hung in front of it and speakers (and such) are contained within the cavity that has been created. What you have is a huge open pathway for the audio to escape, which really messes with the way the audio will perform overall. You also need to consider what type of speakers you want to use and their placement behind the screen area so that you can open up the drywall. That is, the entire point of an AT screen is to have speakers behind it somewhere, and there definitely shouldn't be sheetrock between the speaker and the next room. So, I would open up the drywall a fair bit if you want some decent speakers back there.
I've only done AT screens to this point in rooms using in-wall speakers. Sometimes, pretty high-end in-wall speakers.
But, I have a job coming up where I will have a false wall going into the room and full on floorstanding speakers behind it. I will be making the entire wall acoustically transparent.