How deep a shadow box can you build?

Are you doing an AT screen as well certainly worth it if you are doing 3 ' out anyway then you have plenty of room, you would treat the wall itself not the fake wall but the actual wall with your Linacoustic or 701 or whatever you are using then you build your faux wall 3' out of just framing, and cover that with your Fidelio or GOM etc. and you hang your screen without anything behind it other than the black soundproofing on the actual wall. and you end up with something like this:

The biggest issue with a deep shadowbox is not having it interfere with the PJ shooting onto the screen. You may find that the shadobox may need to be a few inches larger than the screen perimeter to avoid this problem depending on where the PJ is mounted.

You can also frame up something closer (screen doesn't necessarily need to be mounted directly on the real room wall).

Bryan