[Scott Sabin]

I recently uncovered the subject of IB subs, and am intrigued by all the gushing press on the quality of the sound, as well as the neatness of the packaging.

The only way this would work for me would be to use the "enclosed" furnace room. The back 7 feet of my basement is walled-off and unfinished to enclose the furnace, water heater, and provide shelving for storage. This room has about 1100 cu ft of volume, minus that taken up by the applicances, shelves, and other goods. Being a furnace room, I have vents installed at the top and bottom of the wall making the furnace room enclosure to provide combustion air to the gas appliances.

Would this wall work for an IB installation? Since the room isn't airtight, due to the vents, doorway (which can be closed), and airgaps at the top and bottom of the wall, this means the front and rear of the drivers can't be completely isolated. Is this a deal breaker, or is this a minor non-perfection? What details should I pay attention to in order to maximize the performance of the sub?

Thanks!

[ThomasW]

It should work fine. Take a look at the Cult FAQ page for additional info.

Minor openings betweens the adjacent rooms aren't a problem

[Wayne Ernst]

Scott,

I have a very similar setup, but a bit smaller. 320 s.f. for the furnace area/water heater area before deducting the area for these appliances. It's essentially the only area that I have to do an I.B.

I'll look into building the I.B. late this summer and then if it doesn't work out, I'll just patch up the drywall and move on.

[Scott Sabin]

I think I'll look into this a bit more, and keep everyone posted on how it goes. However, I'm not sure when I'll get to it - the base finishing work on the basement is not moving very fast, and I still have quite a task ahead of me before I get to purchasing HT equipment. However, I need to have the plan in place.

The wall that will be used for the IB will be my front wall for the theater. It is not a constant height as I have the main HVAC plenums coming through the top of this wall. Any advice on a where to locate the IB in the wall? It will have to be off-center since that is where the screen will be. Looking for advice on positioning it in both directions. I'm figuring I'll want 3 15" drivers. Thanks.

[ThomasW]

Probably a better idea to use 4 drivers for ease of wiring. Make a cube 18" on a side, or a rectange with 2 drivers on the long sides. There are multiple examples of these install shown in the IB gallery pages

[Scott Sabin]

Thomas,

I assume that is your 12-driver IB sub on those pages. WOW!

When you suggest going with 4 drivers because of ease of wiring, I assume you are saying that provides equal and friendlier amp loading from each driver (assuming 2 pairs hooked up in a serial/parallel fashion, providing an 8-ohm load) versus a 3 driver design? Is that right?

Also sounds like you are suggesting a manifold design. Do these types of IBs have inherent advantages over a flat, in-wall baffle? Is one or the other more forgiving of the vents and door leaks on this wall?

I haven't thought about the manifold design too much. I'm concerned that the added depth into the furnace room might limit where I can locate it. Also, the enlcosure, while simple, seems like more work than a flat baffle. Your thoughts? Thanks.

[ThomasW]

Scott,

Yeap the 12 Shiva IB is mine, I also have a smaller one with 4 Shivas.

There's no sonic benefit to using a manifold over a line of drivers. The primary advantage is having to cut just a single hole in the wall. A manifold is more work up front compared to a line array. A baffle for an array can just be a board of 1-1/2" thick material.

Yes the reason for using an even number of drivers is to keep a 4 or 8 ohm load.

[Scott Sabin]

Thanks for the info, Thomas. The more I look into this idea, the more I see your name. Seems like I have a true expert answering my questions, so thanks for taking the time to share your knowledge.

Currently, I only have the drywall up on the "closet" side, so at this point in time, there is no tear up involved. I'll have to look at which provides the most centered location option for me - manifold, or line array.

Is bracing required on a "flush mount" baffle? I'm thinking probably not with 1.5" MDF (2 pieces of 3/4" laminated). Does the recommendation for mdf/plywood mixture mainly apply to a manifold, or is it equally important for an array design?

I don't know why I'm even asking this last question from someone who has a 12-driver sub, but, here goes. I'm thinking about the Dayton 15" IB drivers. Would I be missing something with just 2, or would that be adequate for a 6000 cu ft rec room?

Thanks again.

[ThomasW]

Yeap I'd use 1-1/2" material for the baffle. Multiple drivers can develop quite a bit of force. I suggest 3/4" MDF glued to 3/4" OSB. Using OSB provides strength, something lacking with MDF. It also does a good job holding T-nuts for mounting the drivers.

The Dayton IB 15"s are good drivers. Given their relatively low cost (note that they're currently on sale for $100ea), I suggest buying 4. That way you're guaranteed you won't suffer from buyers remorse....

There are numerous benefits to multiple drivers other than higher output levels. Distortion is decreased since each driver is not being worked as hard. And there's plenty of 'headroom' for the various kinds of explosions on DVD soundtracks.

When you think about it $400 for drivers, isn't much for a sub that will humble most $5000+ 'box' subs........

[Scott Sabin]

OK, I was thinking the same thing. I've been working on this project for so long that when I'm done, I don't want to feel like I didn't go far enough on something! Using 4 also means (probably) using a manifold design, unless I decide I actually do like the look of the driver array taking up more the half the height of the wall.

Last question, and my plans will be complete. How much extra room should a box side for baffle be? These drivers are 15.125" in diameter. I'm thinking I'd want about an inch at least from the driver to the edge of the board. What's a good board width to use as well as driver spacing?

I'm very much looking forward to hearing this baby. Perhaps if I order the drivers, I'll get down into that basement and get working again!

Thanks again, Thomas.

[ThomasW]

I'd use make a cube with OD of 19" or 20". That would give an ID of 16"-17", with an opening into the room that same size.

If you go with a line array you could cover it with grill cloth.

[Kenneth Harden]

Hmmm, I have a three car garage below my room (evil grin)