Line arrays - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 20 Old 09-23-13, 09:27 PM Thread Starter
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Line arrays

Considering an IB subwoofer for my home theater.

Directly behind the theater's screen wall is a ~670ft^3 closet. I think I'm good to go on the 10xVas issue.

I would prefer to use a 4x line array to minimize intrusion into the closet, and I think the four drivers equipped with wire mesh grills would be add a real macho look to my theater.

In looking through the forum here, it appears that line arrays are not well regarded.

The screen wall is sheathed with 5/8 OSB and a layer of 5/8 drywall. Compared to standard construction, this wall is very solid.

Is there any reasonable way to use a line array, or should I bite the bullet, go with a manifold and live with the closet intrusion?
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post #2 of 20 Old 09-24-13, 08:12 AM
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Re: Line arrays

I have to preface this comment that I'm not coming from any type of experience background other than my engineering background, but a manifold would be much better due to the ability to oppose the drivers which would significantly reduce the amount of work you would need to do to keep everything inert and solid. A line array would need a lot of bracing to keep all that energy moving cones and air and not the wall (which even well-braced I would expect to move and vibrate to some extent).
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post #3 of 20 Old 09-25-13, 02:40 PM Thread Starter
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Re: Line arrays

OK. Here's what my theater look like in Sketchup with 4x15s and two manifolds.

Probably the weirdest thing here is the 2x4 running through the middle of the manifold output area. The wall is sheathed with a layer of 5/8 OSB, then 5/8 drywall. Structurally, I could probably get away with cutting out this 2x4, but would really rather not. Seems like the wrong thing to do given the nature of IB subwoofers.

Any comments?
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post #4 of 20 Old 09-25-13, 03:24 PM
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Re: Line arrays

I like the mockup! The big timber beams give it a very cool look

I believe you need to make sure that your manifold opening area is equal to or greater than the drivers' area. If your openings meet that even with the 2x4 there, you should be good. As for what effect it may have soundwise, I don't know. Regardless, I wouldn't take the 2x4 portion out; I would adjust the positioning or manifold size to get the proper openings rather than deal with potentially load bearing members.
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post #5 of 20 Old 09-25-13, 05:46 PM Thread Starter
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Re: Line arrays

The wall is not load bearing... I know that because I installed it myself.

I do need to make sure I'm OK with Sd... but that's easy. I've got room to make
the manifold taller and wider if need be.
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post #6 of 20 Old 09-26-13, 08:26 AM
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Re: Line arrays

Cool. Then the next thing I would ask is how you will install the drivers. You have the drivers inboard in the manifolds, but no detail whether installed from exterior space or installed into manifolds. If you are installing into the manifold, and don't want to cut out the 2x4s, I would do a sanity check that you have clearance to get the drivers in through the gap.

What are you doing to cover the manifold openings? Cloth grilles, perf metal sheeting?
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post #7 of 20 Old 09-26-13, 09:19 AM Thread Starter
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Re: Line arrays

Although not apparent from the photos, the intention is to load the drivers from the back side. The driver manufacturers don't seem to supply cut sheets, so the precise details of driver mounting will have to wait until the physical drivers are in hand.

The "infinite" baffle is an unfinished storage area. Appearances not particularly important. Probably just a metal grill to keep feet out of the drivers. One thing I have to pay attention to is the access door to this unfinished storage area is somewhat narrow. Hauling the manifolds into the storage area might be a problem. If push comes to shove, I can assemble the manifolds in the storage area.

I was planning on using 3/4 birch ply for the manifolds. I've seen some suggestions that this is insufficient. Given the relatively small size, and that the open end will be securely bolted to a very strong wall, more than 3/4 birch ply seems like overkill??

The plan is for the front (open end) side of the manifolds will be covered with the same material I'm using for the screen wall, which will likely not be "grille cloth". With the extreme air movement generated by the IB subwoofer, this could be a problem??
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post #8 of 20 Old 09-26-13, 09:22 AM Thread Starter
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Re: Line arrays

And one more thing...

It seems the my choice of drivers is AE or FiCar. Any other viable alternatives?

AE and FiCar prices about the same. Any opinions here?
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post #9 of 20 Old 09-26-13, 10:23 AM
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Re: Line arrays

I can only speak to the birch ply question. I don't know how that would be insufficient. 3/4" ply is extremely strong (even junky ply from Home Depot). What it comes to is structure layout. Big panels with no bracing, yeah, you would have a problem, and it would be mitigated less with adding another layer of ply than just properly bracing and building. You can glue bracing ribs on panels to increase rigidity.

If you can design to build then install manifolds without getting stuck in the door, I think you will have a better chance for success than building "on-site" in the storage area. Another alternative to going in through the door would be roughing out the drywall openings and sliding the manifolds through.

As for the screen wall - how close are the manifold openings to the screen? Others will have to chime in here, but I would give a swag that if the distance between your screen and the openings >= diagonal of one of the manifold openings, you are good.

Take a look at Prof.'s HT build with his horn fronts and sub. Granted this isn't apples to apples, but looks like his screen is butted right up to his fronts and sub.
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post #10 of 20 Old 09-26-13, 12:27 PM Thread Starter
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Re: Line arrays

BD55

Attached find a current picture of the theater. Not a great picture, but you can see its a bit more than a Sketchup rendering and its way to late to move manifolds through the walls.

Assembling the manifolds in the storage space is not such a bad thing. The worst part is access to the storage space requires a traversal of the wine cellar which is a no-no .

I am _not_ using an AT screen. IB Sub to screen distance is not the question. The IB Sub openings will be below the screen. I would like to cover up the IB sub openings. The wall behind the screen will be covered in fabric. I would like to hide the subs behind this fabric. I'm worried that this fabric won't be acoustically transparent enough with the extreme IB sub airflow.

And little more background about how I got to where I am... The original plan was to install two "in ceiling" off the shelf subs in the soffits that are just barely visible in the top of the picture. As I started to seriously consider this, several issues became apparent. (at the risk of offending an owner ) I looked at the in ceiling offerings and decided than in addition being lame, they're rather expensive. Also the soffits are within the acoustic envelope and are not heavily built. I'm concerned that the subs will rattle, or I will have to do a bunch of work to prevent rattling.

Looked into the IB Sub thing and I have a pretty good "infinite" baffle, but I didn't originally plan for an IB Sub... so I've some challenges.

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