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Author Topic: Baffle wall question Steven Smith Film Handler Posts: 35 From: Boyce, La/ USA Registered: Jul 2014 posted 06-12-2015 02:11 PM                     Hey guys, I'm not really sure what section this should go in as I don't see a construction type of section. Sorry if it's in the wrong one. So I have a (L)21'6"x(W)16x(H)10'4" theater room(new construction). It's new construction. I have a foyer with a ramp that leads to the back riser and 2nd row, the riser steps down 16" to the front row. The rows will be at 12' and 17'. I plan on building a baffle wall 18" off the back wall. I have 3 QSC 2150s for the front stage. I have a few questions about the baffle wall. I'm using 1.5" ductboard (OC 703) to line the front wall and face of baffle. Should i put a slight angle on the baffle for the L/R speakers to help with imaging or just aim all speakers straight forward? Does the baffle have to be air tight around the speakers or can I just fill any small gaps with fiberglass board? The screen will be 165" 16:9 so all 3 will easily fit behind the acoustic screen.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 06-12-2015 03:06 PM                     Ductboard is NOT really the right thing to line a baffle wall with. Two sheets minimum of 5/8 gypsum covered with the correct Johns Manville lining that comes in sheets or rolls. Three sheets of 5/8" gypsum is even better. Johns Manville fuzzy glass stuff that gets all over you! ^Accept no substitutes... and the stuff can be difficult to find in some places. Mark  |  IP: Logged Steven Smith Film Handler Posts: 35 From: Boyce, La/ USA Registered: Jul 2014 posted 06-12-2015 03:26 PM                     Thanks for the info on the Gypsum. That answers that question. The ductboard is OC703 compressed fiberglass. It has the same coefficient properties as linacoutic etc even down to 250hz. It's very reasonably priced and I can get it locally. http://www.bobgolds.com/AbsorptionCoefficients.htm As for the wall, should I toe in the side baffles slightly? How sealed does it have to be around the speakers? Also if I remember correctly Mark you've installed a few 2150s and liked them. Were they installed in baffle walls?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 06-13-2015 08:56 AM                     I'd have to see a whole room drawing to see if you should curve the wall or angle the sides. It's not always necessary or desirable. None of my 2150's were in baffle walls but they were all in smallish theaters with less then a 50 foot throw. Is the OC703 black or yellow? If it's yellow that may be a problem. If you can get it in black you should. The linacoustic is black. Mark  |  IP: Logged Steven Smith Film Handler Posts: 35 From: Boyce, La/ USA Registered: Jul 2014 posted 06-13-2015 09:27 PM                     Thanks for offering to give me some advice Mark. Yep the duct board is black on the facing. As for the layout I don't think this forum will allow me to post it. If you don't mind clicking on a link, I linked my build thread with the layout and pics of the room all in the first post. Thanks. [ 07-13-2015, 04:35 PM: Message edited by: Brad Miller ]  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 06-14-2015 02:53 PM                     I don't think your room is wide enough to worry about angling the sides ofvthe baffle. Aim through the HF driver port with a laser to a point about three feet above the rear center seat when aimimg the speakers. Stereo imging should be very good Mark  |  IP: Logged Steven Smith Film Handler Posts: 35 From: Boyce, La/ USA Registered: Jul 2014 posted 06-14-2015 05:06 PM                     So your saying build a flat baffle wall and install the speakers with no toe in and aim 3' above the back row... Correct? You said center seat but that would require toe in and the speakers have to be flush with the wall.. Correct? I may not be following you, I was under the impression that with a baffle wall the speakers had to flush to the wall and sealed to the wall with no gaps around the edges. Also... Do you think the benefits of a baffle wall are big enough to make it a good idea? If the benefits are small heck I'll just put them behind the screen without building a full out baffle wall.  |  IP: Logged Mike Blakesley Film God Posts: 12767 From: Forsyth, Montana Registered: Jun 99 posted 06-14-2015 11:06 PM                        It makes a difference. We went to a baffle wall when we changed out our speakers (went from 2-way Peavey to 3-way QSC). I guess I don't know how much of the difference is attributable to the wall and how much to the speakers, but it's a lot better since we added the wall. Better dialog intelligibility, for one thing, and a much tighter sound. I guess I don't know how much difference a baffle wall would make in a room that small though.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 06-14-2015 11:31 PM                     Anyone serious about quality sound will put in a baffle wall. It ALWAYS helps. I wouldn't have put one in my screening room if it didn't make much of a difference.  |  IP: Logged Steven Smith Film Handler Posts: 35 From: Boyce, La/ USA Registered: Jul 2014 posted 06-15-2015 11:25 AM                     I'm thinking of using mdf for the wall facing covered in the duct board. So how big should the gap be between wall and speaker? 1/4"? Do I need to fill the gap? Speaker to the edge of mdf or acoustic materials edge?  |  IP: Logged Steven Smith Film Handler Posts: 35 From: Boyce, La/ USA Registered: Jul 2014 posted 06-15-2015 06:17 PM                     Thanks guys for the nudge to stay with the baffle by the way, I'm sure I'd regret it if I didn't do it. Any info on my questions related to gaps and how sealed it needs to be around the speakers or any tips would be greatly appreciated.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 06-15-2015 10:55 PM                     MDF is a really bad idea. Its not dead enough and fireproof mdf is gonna cost a fortune. All in all its the wrong stuff. 5/8" drywall only.The wall itself needs to be very dead and non resonant.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 06-16-2015 08:58 AM                        The best baffle wall is marble faced with duct liner (fuzzy side out). The closest I have come is a guy in Michigan who had about 50,000 record albums on industrial shelving on both the back wall and also just behind the screen. True "bookshelf" speakers, just industrial sized speakers AND bookshelf. What you are looking for is MASS. According to JBL designers, Mark Gander and John Eargle: "NO speaker ever made will meet its spec without a sound wall." JBL has a lift that puts their speakers in a roof hatch in plane with the finished roof. A microphone is mounted on a small tower above it.  |  IP: Logged Steven Smith Film Handler Posts: 35 From: Boyce, La/ USA Registered: Jul 2014 posted 06-16-2015 10:40 AM                     OK, materials are being delivered today. I changed to order to 5/8 sheetrock. Double layers. My biggest remaining question is how to handle the gaps between speaker and baffle.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 06-16-2015 07:04 PM                     Put the studs up and frame out the opening where the speakers go. A small platform on the rear is usually good enough for each speaker.Can't really tell you where to put the sub at because I donno if you are building on top of a stage or on a flat floor. If on a flat floor about 12" up from the floor is good for the bottom of the sub. Then put one layer of drywall vertical and the next layer horizontal. Three is THX spec usually. I have done walls with two layers, especially where the weight of the wall wold become worrisome. It is recommended to tape each layer... Depending on how good a taper you are so have fun with that! Then cover the entire wall with duct liner and cut the openings for the speakers but leave several inches of duct liner around the hole. When you slide the speaker cabinet in the duct liner will push it's way back around the speaker and seal the hole up around three sides of the cabinet. Fill in behind the mid-high frequency unit with another sheet of the stuff as needed to make it nice and neat and closed off. The following pictures should give you some idea... This one took about 5 days to build and get the screen back up. This wall got two layers of 5/8" drywall because we ere concerned about all the weight on the stage. I believe the theater owner did have the county architect inspect under the stage before this went in so we were ok on weight. Mark  |  IP: Logged

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