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Sealed vs Open Room - definition?

post #1 of 10
Thread Starter 
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?

Thanks,

Dan
post #2 of 10
I don't know of any hard-and-fast rule, so, IMO, I'd consider the size of the opening relative to the size of the room.
- A 1" gap or a set of FA vents is negligible.
- A regular doorway in an average-sized room could be a compromise, but one that a reasonably-powerful sub could/should be able to overcome. (IOW, no need for massive or multiple subs.)
- A similar sized doorway in a very large room would be even less of a compromise; vice-versa, more of a compromise.
- Et cetera.
post #3 of 10
A "sealed" room does not have to be airtight to behave acoustically the way we would expect a sealed room to behave, i.e providing large amounts of room gain as the frequency goes down. A room with a doorway will be virtually sealed if the door is closed even if there are air gaps. With the door open, it would behave something less than sealed, but should still provide most of the gain benefits of a sealed room. When you get into an opening that is large such as 12' wide, it is an open room.
post #4 of 10
Thread Starter 
Got it. Thanks. That's pretty much what I had expected, but began to doubt it based on the threads about people sealing things up so tightly.
post #5 of 10
Some ppl with a sealed room actually open their door when they are using their system.

In my room if I open my door I get a lot less rattling of objects in the room. Also with the door closed my door slams back and forth in the door jam creating an annoyance sometimes.
post #6 of 10
Indeed and to give you another example, in my basement , I finished sealing the HT room and putting two doors to divide in half and guess what...I get better performance with both doors opened!
So with room acoustics you never know is my rule...you have to try
post #7 of 10
Quote:
Originally Posted by flickhtguru View Post

Also with the door closed my door slams back and forth in the door jam creating an annoyance sometimes.

Try using weather stripping to prevent the rattling. That's what I do.
post #8 of 10
Quote:
Originally Posted by duc135 View Post

Try using weather stripping to prevent the rattling. That's what I do.

Me too, huge difference! I have 4 doors that rattled like crazy and now none at all, or close to it. This is a must IMO.
post #9 of 10
Quote:
Originally Posted by duc135 View Post

Try using weather stripping to prevent the rattling. That's what I do.

Yeah I'll do that eventually when I get to it lol. My room sux by the way for HT... Its a basement that the previous owners finished themselves. It has paneling walls and no insulation behind the paneling and it wasn't fit properly or not enough nails were used so the paneling rattles. Also there is a shelf "thingy" built into the room and in that area the only thing that seperates the living room from the furnace room is 2 pieces of peg board one on either side of the wall. But we are either moving or going to gut the basement and start over.
post #10 of 10
Quote:
Originally Posted by Luis Gabriel Gerena View Post

Indeed and to give you another example, in my basement , I finished sealing the HT room and putting two doors to divide in half and guess what...I get better performance with both doors opened!
So with room acoustics you never know is my rule...you have to try

Very true, room acoustics are weird. I had my sub in one front corner, I moved it to the other front corner and I gain 6db spl and without re-calibrating or re-EQing I would litterally blow pictures off the walls. I even kept the sub placed the same distance to the side and back walls as in the other corner.
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