Drop ceiling tile options?

the7trumpets

New member
I'm relatively new to this forum, but I have read enough to know many of you really understand what's really necessary to achieve the desired acoustics in a room through size/shape of the room, broadband absorbsion, bass traps, and diffusion. I hope you will forgive me for asking a question which is about a larger non-studio space, but most people who build or treat larger spaces simply don't have a clue about acoustics. :(

For several years I engineered in a medium sized ($95/hour) commercial studio and helped in a very substantial rebuild of thier control room and booths, so I am a very familiar with OC 703 and 705 (gosh I hate that glass fiber itch!), and concepts of sound isolation and treating of rooms.

Now I find myself in a different situation, and I hope you can offer some ideas.



The Situation

Some friends of mine are starting up a church in a former church building. The building was acoustically awful to begin with, and is even worse for the types of things they want to do. The music style will be a smattering of hiphop and rock so it will have live drums and will contain quite a bit of low end content. A lower RT60 time would not be a bad thing since there will be almost no completely acoustic content.



The Room and Plan

It's an A-frame room, approximately 50 feet wide, 58 feed deep, and the ceiling goes from 8 feet at the side to about 19 feet in the center. The ceiling is a drop ceiling.

My plan is to treat the wall behind the stage and the wall opposite it with 4" semi-rigid fiberglass or rockwool spaced 4" from the wall. Then I will put even deeper bass traps in the vertical corners and side walls next to the stage since that is the zone in the room where the low mid nodes are most objectionable. As you can immagine, the wooming low mids find thier way into all the mics making the problem even worse.



The Problem

My problem is with the ceiling. Currently the drop ceiling has fairly dense ceiling tiles coated with some sort of thick vinyl. The large flat surface which seems to reflect everything above about 250Hz is problematic so I'd like to replace it with absorbsion and diffusion, adjusting the ratio between diffusion and absorbsion to attain the desired reverb time.

Tearing it down and rebuilding a new ceiling is not really feasible for them because of budget considerations, so I've tried to find 2'x2' ceiling tiles that actually absorb and don't reflect even at oblique angles. So far, everything I've found seems questionable or really expensive. Do you have any suggestions?

Ideally I'd find something that looks descent and costs around $0.50/sq ft ($2/tile). It doesn't need to be all that thick or have a high absorbtion coefficient in the low mids since there is a fair ammount of R13 insulation above the ceiling, and putting more up there is fairly cheap. It cannot however reflect much mids or high end, especially at oblique angles.

I considered just cutting 1" OC703 2'x4' panels in half, but covering them with burlap and getting the grain to go straight without sagging seems quite difficult so if there were a pre-manufactured solution I would prefer that.

Also if you have any suggestions for 2'x2' ceiling tile diffusors that are fairly cheap, let me know. I'm not looking for anything as diffuse (or expensive) as ART diffusors or T-fusors, it just needs to be easily installable in a 2'x2' drop ceiling and break up the big reflection zones.



Thanks!
 
The trapping around the former altar could be excessive. This is a large space, I can imagine a big RT60, but with a drop ceiling--what is the flooring?--it could be worse. I wouldn't think the nodes are too horrible, and completely coating the space until it is dead, dead, dead--I don't see the point.

For the ceiling, just hang 4" sheets of fiberglass horizontally, suspended from the peak of the ceiling. Vertically works too, but doesn't look as cool :cool: I gather this is a low-pitch roof, so another row of such baffles on either side might be in order.
 
Thanks for the input. I hadn't thought of simply hanging absorbtion at the peak of the ceiling, but that may be just enough for the ceiling. In any case, it's easy to do that and then evaluate whether further absorbtion in the ceiling is necessary. I was just searching for a more 'invisible' solution that wouldn't give the interior an acoustically treated look.

Like you, I expected that the large space would mean that modes in the low mids would be less of a problem than a smaller room. However, when walking around the stage when program material is playing (live or through the system) I hear wide variations in low end and low mid resonances. I suspect it has something to do with the close length and width dimensions, and in general I have noticed more low mid annoyances in A-frame shaped rooms than in rectangular rooms.

The floor is that annoying commercial low-pile carpet, but you are right that the situation could be a whole lot worse than it is. And thanks for reminding me that making it completely dead would be bad. If too much absorbtion is put in it would 'feel' weird when you're in there. I'll probably reccomend they do it in stages to ensure that it doesn't become too dead, but that low end really needs to be tamed for what they want to do in there.
 
the7trumpets said:
solution that wouldn't give the interior an acoustically treated look.

You can make them look quite nice, like this:

http://www.acousticalsolutions.com/products/banners/alphasorb_baffles.asp

You should be able to roll-your-own for about half their price.

I suspect it has something to do with the close length and width dimensions, and in general I have noticed more low mid annoyances in A-frame shaped rooms than in rectangular rooms.

Sure. But there's a difference between treating a room for live sound and studio use. Given the distance between walls, the reflections will drop quite a lot in dB before they reach the mics. Unless you are primarily using distant micing techniques, I suspect this will be less of an issue, especially once you hang some panels.

Are you going to frame around the altar for a control room?

Oh yeah, and tear out that carpet :)
 
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