I'm planning on adding a return vent in my media room to help vent the warm air from a newly installed ceiling-mounted projector. My system currently has two return vents (a 30x24 and a 12x12), and I figured adding another 12x12 return (or 18x12) won't adversely affect things. At least I keep reading that it's very difficult to oversize returns.
I've been doing research online and at Lowe's/HD to see exactly what I'll need to get, and the part I'm still unclear on is the boot or box (or whatever it's called), where the flexible duct terminates right behind the grille. Is there a name for this? Is it the same as a register box/boot? Or is it something different? All I could find were register boxes at Lowe's/HD, and nothing called a return box.