Noob - Sub help!

[spidrman]

First time for me to post here. Been reading as much as I can before asking but I can't find a specific answer to what I'm trying to do.

I'm just now starting on my HT room. It's 12' x 22.5' with 9' ceilings. I've been reading up on every kind of sub there is and thought I was going to build an infinite baffle sub into the ceiling with two 15 or 18 inch subs with the possibility of adding two more down the road. Unfortunately when I went in my attic I discovered that due to structural reasons, I can't do an IB where I want it. It would end up having to be about 1/3 the way into the room lengthwise and that just doesn't seem to be a proper location. If that wil work fine then I'l still go that route.

My alternative is to build a BIG box that would go under the screen. This box could be as large as 10' wide, 18 inches deep and 22 inches high (all outer dimensions). This is about 25 cubic feet of volume. I want two 15" subs more or less centered in this box facing forward. I'm looking for deeeeep bass.

I've pondered making this a single big sealed box. Splitting it into two sealed boxes. Two ported boxes. And even making it into a transmission line sub.

I'd like to do this on a budget of say $700 or less including an amp.

I'm just looking for suggestions. Point me in the right direction. Give me the pro's and cons of different setups. Tell me I'm nuts if I am.

Any suggestions would be great!!

[ThomasW]

What's the structural issue with the attic location?

[spidrman]

The front wall where the screen goes is an outside wall. Due to the way the house is built, there is a "wall" in the attic that I can't reasonably get to the other side of. It is about 7 feet in from the front wall in the theater room where the screen will be. If I could get to the other side of this wall I could still do the IB sub. Or I could do all the work from the bottom and have the sub's manifold hanging from the ceiling since the screen (and curtains) will hide it. But this would mean moving the screen farther from the front wall which I don't really want to do.

[ThomasW]

Several people have done installs from the bottom. Doing so just takes a little more planning than doing to the other way.

I don't understand why in your instance this would require having the IB hang down?

[spidrman]

The side view of the room/attic looks something like this:

                                |    \
                              W |     \
           ATTIC              A |      \  <-- Can't get inside there from above.
                              L |       \
                              L |        \
------------------------------------------
                                         |
                                       S |
                                       C |
                                       R |
                                       E |
                                       E |
                                       N |
                                         |
                                         |
------------------------------------------

The "wall" in the attic is built just like an interior wall. 16" spaced studs and it has some type of 1/2" thick insulation board nailed to it on one side. Even without the insulation, I would have to cut out at least one support to be able to get access to the space over the screen area in the front of the room and I'm not comfortable removing things that hold the roof up. Putting the IB on the accessible side of the wall in the attic would have it about 7 feet in front of the screen which from what I've read will give me phase issues.

[ThomasW]

Manifolds have been prefabricated then installed in sections from below without removing any structural elements. The drivers can also be installed from below if one plans correctly.

Test the performance at the 7' location per the instructions on the IB FAQ page. Who knows? It might work just fine.

[spidrman]

Cool ... I hadn't considered the "ship in a bottle" method of construction ...

One other question then. If I can get the location where I want it, It will basically be right over my screen and some curtains. Should I be concerned about the output at high levels making the curtains or screen flutter?

I'll be using my small 10" box sub to test the location I want (need to borrow a taller ladder) and will also test the other location as well.

[ThomasW]

The output level would need to be exceeding high to cause a screen to move.

I can blow a small towel off the opening of my floor mounted IB, doing so involves an output level so high it certainly wouldn't be used in any 'normal' listening situation.

[---k---]

The output level would need to be exceeding high to cause a screen to move.

I can blow a small towel off the opening of my floor mounted IB, doing so involves an output level so high it certainly wouldn't be used in any 'normal' listening situation.

Really, I could swear I've read about some people's bass making their pants flap.

[spidrman]

Well ... I think the IB is out ...

Well after climbing around in my attic some more and crawling around with a flashlight, it appears that doing an IB sub in the front of my theater room is not going to be possible. Here is a pic of the front of my house:



The upstairs room on the left is the theater room. The screen is going in front of the window. The area in the attic over the screen area is that tiny peaked roof. The clearance in there is not high enough for a manifold and that area is almost sealed off from the rest of the attic.

Here's a shot of the theater room from the inside (this project is just starting):



The screen is going to be flush with the front of the corner square "columns". Those are some old Jamo speakers that my wife had when I met her. They were fine in our old house in the family room for normal TV watching but they don't cut the mustard for home theater. I'm going to try putting the sub in the picture on a ladder and try a spot about 8 feet from the screen but I just don't think that being that close to the center of the room is going to work properly. So I may be back to making a big sealed sub with a pair of 15" subs for under the screen.

Any thoughts?

Thanks!!

[ThomasW]

Any thoughts?

Thanks!!

If possible pics or real drawings of the attic design would be handy