[3aSig]

Hello everyone,

After years of reading about all the great projects on this forum, I've decided to jump off the deep end. I went out and bought myself an A-lens, decided to build a DIY curved screen, and, lastly, upgrade my low end bass.

To that end, I've decided to try and do a 4 x IB318 setup. My plan is to install the drivers as a line array in a converted closet (the soda fountain in the pictures below will be moved). My problem is that the closet is only about 7,000 L, about ½ the of the required 15,240L to get to 10x Vas. However, the closet connects to an unfinished basement through an opening that is 12" wide by 105" tall by 58" deep.

The reason for this small opening is that a wet bar was built into the closet area. I'm really hoping I don't need to demo the bar. I'd much rather just cover it with a curtain. Also, the ceiling in the closet is unfinished and opens (very narrowly) to the ceiling in the theater room. My question is, will the closet opening act as a vent (and mess everything up), or will I be able to get a true infinite baffle sound?

Thank you in advance for your response.

 

[Mike P.]

There's absolutely no reason to demo the bar. Whether you obtain the "ideal" 10x Vas or half of it, the output with the IB318's will be the same. You're good to go.

I'm not sure I understand where they will be mounted. In the first pic it shows 4 drivers. Are they mounted on a baffle that replaces the closet doors?

 

[3aSig]

Mike,

Thank you for responding so quickly. People like you make this forum what it is - which is great. To answer your question, I plan on removing the doors to the closet and building a new wall out of plywood or MDF, or a combination. I will mount the four drivers in that wall. Right now, I plan on doing a line array, but I may do a manifold to cancel some vibration.

Thanks again.

 

[ironglen]

Looks like a great project. I would think a couple manifolds would be preferable; perhaps someone else can give a definitive answer on the matter. Once you find out, document with lots of pics as IB installs are not common :T

 

[Mike P.]

If you're going to do a line array I would suggest using plywood, and make sure it's well braced.

 

[3aSig]

Thanks for the responses. I do plan on documenting the build. I just put the order in for 4 IB318's (2 Ohm). I hope they ship early. I plan on buying an EP4000 as the workhorse amp.

Until then, I get to do the dirty work and ready the closet. Any good plywood wall builds out there? If not, I'll just brace it and pray.

 

[aaron smithski]

You actually have a soda rack that houses 6 bag-in-the-box syrups for your house? That is hardcore! :T

 

[ironglen]

You actually have a soda rack that houses 6 bag-in-the-box syrups for your house? That is hardcore! :T

I was thinking the same thing! With a setup like that, you could host the HTS Holiday Regalia!!! :rofl:

 

[3aSig]

Ha. The soda fountain came with the house. It's a blessing (really fun) and a curse (a constant leaky sticky mess). I think it's rated for like 120 servings per hour. We do, maybe 5, per day. Anyway, I finally broke ground on the project and pulled the doors and trim. I can't do much more until the drivers get here, hopefully before 2013 rolls in. Sorry for the inverted pictures. I'm still in my forum infancy.

 

[ironglen]

Are you going with an array, or manifolds? Either way, you could be pretty creative with that panel, if so desired. I think even your driver layout is open since it is low freq based. My biggest concern would be protecting cones from unintended impact (kids, pets, careless people:whistling

 

[zacjones]

Looks great an IB should do very nicely in that space. You mentioned the closet opens up to the ceiling above the theater -- you mean like into the rafters above the drywall? That should be fine I'd think, but I can't really make it out in the pictures. As Mike mentioned 4-5x Vas is also OK for IB installs.

What's your plan for the center channel? Is this an AT screen you're building or are you going to place the center above or below the screen? If you're considering AT I'd recommend the reasonably priced and super nice Seymour xD screen material for your DIY screen with the center channel where you have your IB modeled. That'd leave you plenty of room below the center channel to either do a pair of manifolds or a nice long array of subs along the bottom under the screen. I think that'd look pretty sweet with the 4 driver horizontal array under the screen. I can still see my drivers pounding away some in my IB manifolds, but I do miss seing them showcased.

Looks like you wouldn't have any problem at all bracing the line array (which is by far the most critical issue to deal with in an IB array) with all that sturdy concrete on the floor and back wall to tie into. If you use wood for bracing just make sure you screw AND glue. I'd use simpson strong ties wherever I could as well. I vote for a visible line array below an AT screen unless you're concerned about stray feet kicking the drivers. Looks like it's off the beaten path though. Nice to see another IB build gaining some momentum!

 

[3aSig]

Ok everyone,

Thanks for all the encouragement and advice. I've made some significant progress in the room, but still don't have the drivers. Thanks to Amazon, my EP4000 is here. Too bad it's probably gonna sit around until after new years.

To answer a few questions, my overall plan is to build a 130" wide DIY curved AT screen (Seymour xD should have shipped today:T) that is placed 2 feet off the rear wall and masked with wall-to-wall curtains. Behind the false drapery will sit my mains, center, and the subwoofer array.

I plan on placing the subwoofer drivers in a 2x2 array, seated in two laminated ¾" sheets of Maple plywood (1.5" total thickness). This baffle will itself be mounted on the framed out wall constructed of double studded 2x6's with (yet to be added) wood bracing and anchored to the concrete floor/existing doorway framing. I'll then seal the whole thing with some sort of sealant (suggestions, as always, are welcome and appreciated).

The center channel will be placed in front of the subwoofers, centered between the four drivers. Please let me know if this is a bad idea. I figure the crossover point will be between 50-80hz and the subs won't really care if there's a center in front of them. It might only be problem if I upgrade to a full range, floor standing, center. And, even then, I doubt I'll hear (and definitely won't feel) a difference.

The closet opens to the drop ceiling in the basement/theater area (which Zac correctly assumed). In addition, the closet also opens to an unfinished portion of the basement, through an opening that is roughly 12" x 105." Thanks to Mike, I now know that these openings should not act as a "vented" enclosure.

If, after all this, the drivers are too ferocious, I'll try and secure the framing to the rear cinder block wall with some steel rods. Zac, on this subject, would you please explain which model of Simpson ties you recommend?

Thank you all again.

 

[zacjones]

Regarding fixation of the steel rods -- do you have access to the other side of the concrete wall? I think it'd be ideal to drill through the concrete, run some threaded rod through the wall and put nuts and washers on both sides to anchor. They make some simpson strong ties that look like they would work very well for this kind of thing, providing a 4x4 post anchor with threaded rod extending out the other side. You could then tie 4x4's into the strong ties, and you could do it again at the other end with the plywood, with the less complicated strong ties. But I'm not a professional -- I've just used some of the strong tie stuff mostly with wood and a couple times with concrete slabs in remodeling. I would consult some of the seasoned veterans over at the cult as many over there have built arrays and probably have some better insight and ideas. But nevertheless I'd recommend you take a stroll through the strong tie section at Lowe's or Home Depot and see if you get any ideas. I've seen some stuff that looks like it could be useful in this type of application. I don't know about using steel rod for support. It might work, but I'd think 4x4's would be fine, or if you want to use steel some type of corrugated tubing would be better, stiffer, and cheaper. Looking good!

How wide is that narrow opening to the drop ceiling? If it's really narrow and in the back of your mind you're wondering about complications, you could always block it off with a 2x4 or 2x6 and hit it with a can of spray foam insulation. But again, I'd measure the width of the vent, take a good picture of it, and ask Thomas over at the Cult about that one just to be sure. I'm still thinking it'd be fine though, especially if the "vent" is 12" and the entire drop ceiling is 12". If the "vent" is 4" and the area behind the vent is 12" deep, I'd be more concerned, and even though Mike is an excellent resource with a lot of experience, I'd try and get as much input as I could from as many knowledgeable folk as I could.

Framing's looking good. How did you anchor the bottom plate (flat 2x4's) to the floor? I'd make sure and sink some big concrete screws through those. I'm all about overkill, so I'd probably run some 4x4's to the back wall along the floor as well, tie them into the back wall, then sink in concrete screws everywhere.

Keep up the good work!.

 

[zacjones]

The center channel placement should be fine. Just make sure you get L/C/R that are designed for "on wall" use. I would also at least consider walling off the bar so the response from the L/R speakers would be the same, unless you're confident audyssey or some EQ can tame the differences behind an on wall speaker and a speaker 2' from the rear wall. Demoing the bar would give you more VAS and solve this issue. What mains have you chosen?