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Church acoustics
Over the last 6 - 10 months I've posted a few questions about improving the
acoustic performance of a church. It seems that funds are now available, and that the work can proceed. The room is approximately 40' x 55'. Currently there are brick walls on 3 sides, 20 -40 ft assymetrically sloping pine board ceiling, floor is covered with thin carpet. The room is 95% used for band style worship, (drums elec bass, amplified guitar, 4-8 vocal mics). The problem is excessive reverb time reducing speech intelligibility and making the music muddy. The plan is to construct 2" x 4' x 8' 703 panels covered with fabric. These panels will be mounted to the walls, with a 2" spacing between panel and wall. The panels will cover approximately 40% of the brick wall area. Is the material used to cover the panels important? It has been suggested to me by the church people that they may want to cover them with the same carpet as the walls. Will this be a problem? Do you see any other problems with the overall plan? Thanks for your time -- John Cafarella End Of the Road Studio Melbourne, Australia |
#2
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Church acoustics
John,
The plan is to construct 2" x 4' x 8' 703 panels covered with fabric. That all sounds good. But you might consider making some of the panels twice as thick, and putting those on the walls near the corners. That would help reduce the low end mud a little more. In fact, even better is to built thick panels just for the corners, and mount them straddling the corners at a 45 degree angle. they may want to cover them with the same carpet as the walls. That should be fine. The fiberglass will just extend the carpet's absorption to a lower frequency. --Ethan |
#3
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Church acoustics
"John Cafarella" wrote in message ... The problem is excessive reverb time reducing speech intelligibility and making the music muddy. The plan is to construct 2" x 4' x 8' 703 panels covered with fabric. First, a caveat - I'm not an expert in this field, but I have done some of this kind of work, and I have had some acoustical physics coursework in college (100 years ago). It seems to me that what you propose is designed for high-frequency absorption, but I'm afraid that the lower frequencies may be causing the bulk of your trouble, and I don't think your solution will address this. I've seen similar attempts at solving intelligibility problems that only made things worse by absorbing useful high frequencies while leaving the lows bouncing around the room, still masking everything above them. I would recommend adding some dispersion to your plan. You can make wall units that look the same as the others, but have acoustically invisible (or nearly so) fabric on the front, with a convex hard surface behind. The curved surface will reflect the lower frequency waves back in a scattered pattern which will allow them to decay more naturally in open space without reflecting off of opposite walls creating standing waves. Or you could simply make all of your panels curved, making them a high-frequency absorber and low-frequency diffuser in one. Of course, since you say you are building "703" panels, and I don't know what those are, perhaps they are already curved and you already have this covered. Bill Balmer |
#4
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Church acoustics
"Ethan Winer" ethan at ethanwiner dot com wrote in message
... John, The plan is to construct 2" x 4' x 8' 703 panels covered with fabric. That all sounds good. But you might consider making some of the panels twice as thick, and putting those on the walls near the corners. That would help reduce the low end mud a little more. In fact, even better is to built thick panels just for the corners, and mount them straddling the corners at a 45 degree angle. they may want to cover them with the same carpet as the walls. That should be fine. The fiberglass will just extend the carpet's absorption to a lower frequency. --Ethan Ethan, Good thought about the double thickness panels. I hadn't given this much thought as my research seemed to indicate bass buildup in corners is not so much of a concern in a large room as it is in a small room such as a control room. It's largely academic anyway as there are doors in EVERY corner of the room, so that's not practical. The closest I can get is adjacent to doors on only two walls. Would this still be worthwhile? If these panels are 4" thick, they should be 4" off the wall, correct? One other thought, will the performance of two 4' x 4' panels (not butted up against each other) be less than the perfomance of a single 8' x 4' panel. I ask because in some positions the spaced smaller panels may work better aesthetically. -- John Cafarella End Of the Road Studio Melbourne, Australia |
#5
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Church acoustics
John,
my research seemed to indicate bass buildup in corners is not so much of a concern in a large room as it is in a small room such as a control room. Large rooms are often very boomy, and have an excessive reverb time at low frequencies. If all that matters is speech intelligibility, then you don't have to worry about low frequencies. But if you EVER plan to play music in there you should definitely aim to reduce the reverb time at low frequencies too. It's largely academic anyway as there are doors in EVERY corner You can also use the corners formed at the top of the walls where they meet the ceiling. If that's not practical, then do as you suggest and just put the double-thick panels as close to the corners as you can. And again, spacing the panels away from the wall extends their absorption to lower frequencies. The ideal air gap is approximately equal to the thickness of the panel. will the performance of two 4' x 4' panels (not butted up against each other) be less than the perfomance of a single 8' x 4' panel. Cutting the panels in half will actually be a little better. If you have X amount of material to cover the walls, then you're always better off distributing it evenly. That is, alternating panels - for example, in a checkerboard pattern - is always better than covering large areas. --Ethan |
#6
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Church acoustics
"John Cafarella" wrote in message ... Feel free to correct me if I'm wrong, but to be non-transparent (therefore reflective) at low frequencies wouldn't a curved panel have to be quite massive and rigid? (and hence expensive) Yes and no. I have seen good diffusers made from "sono-tubes" cut in half lengthwise. These are generally used as forms for poured concrete pillars. They are made from a thick, pressed paper product (think halfway between MDF and heavy cardboard) and are fairly inexpensive. When painted to match the room, they can be quite unobtrusive and effective. Anyhoo, I'm not convinced that this room needs any more diffusion. Okay then. Of course I've never been in the room, and you're probably right. Chalk it up to an exercise of useless theory! Good luck, and let us know how it goes. Bill Balmer |
#7
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Church acoustics
"John Cafarella" wrote in
: Over the last 6 - 10 months I've posted a few questions about improving the acoustic performance of a church. It seems that funds are now available, and that the work can proceed. The room is approximately 40' x 55'. Currently there are brick walls on 3 sides, 20 -40 ft assymetrically sloping pine board ceiling, floor is covered with thin carpet. The room is 95% used for band style worship, (drums elec bass, amplified guitar, 4-8 vocal mics). The problem is excessive reverb time reducing speech intelligibility and making the music muddy. The plan is to construct 2" x 4' x 8' 703 panels covered with fabric. These panels will be mounted to the walls, with a 2" spacing between panel and wall. The panels will cover approximately 40% of the brick wall area. Is the material used to cover the panels important? It has been suggested to me by the church people that they may want to cover them with the same carpet as the walls. Will this be a problem? Do you see any other problems with the overall plan? Thanks for your time -- John Cafarella End Of the Road Studio Melbourne, Australia How about some poly's ala the late great Malcolm Chisholm? Build then in boxes and hang on the wall. His son reposted his website, Link he read fuzpoly.txt: http://pages.ripco.net/~chisholm/mal...holm/INDEX.HTM They are basically bowed masonite; simple; dirt cheap, and as Malcolm told me; nobody believes they work. I've built 4. Also from Malcolm; he mentioned that a certain research lab told him that 6" of 703 theoretically absorbs lower torwards 60hz. "Theoretically" because their anechoic chambers could not measure that low due to their size -- room smaller than the wavelength sizes. Best, Mack |
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