In calculating cubic volume in order to determine how much sub you need, people often refer to "open" or "sealed" rooms, since if the subs aren't used near-field, they'll need to pressurize the whole volume.
My question is - what does it mean to be "sealed"?
I know that a 7'x12' opening would make almost any normal room "open".
I know an airtight room would be "sealed".
But what about a 3'x7' open doorway in a 12'x16' room?
How about a similar room, with a closed door, but with a 1" gap at the bottom?
What about nicely closed doors, but the room has forced air vents (incoming and return), and gaps through outlets and light fixtures, etc.?
So, how sealed does it need to be for the purposes of calculating cubic feet?