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Author Topic: Speakers on an open stage. Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 04-08-2009 01:45 AM                     I'm working on ways to upgrade our sound system. Our theater is a regular stage with the screen flown in, not a normal cinema. Our speakers are on roll away carts because we have to strike them after the movie is over to make way for other shows or events. Consequently, when they are in place the speakers have to sit in the middle of the open stage, behind the flown screen. We lose a lot of sound in that big, empty box behind the screen. I'm thinking of ways to solve this, if possible. Up till now, I have been flying in the large mid-stage traveler curtain behind the speakers. It helps but curtains don't do much to stop sound. They only muffle it a bit. My idea is to rebuild the speaker carts so that they have fold-out panels on either side. In can roll them into place then open the wing panels, sort of like a set of French Doors so they will make a solid wall behind the drivers. I can build them like Hollywood flats and hinge them together. Here's an animation I made: http://homepage.mac.com/randystankey/.Movies/speakers.mov Do you think this will work?  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 04-08-2009 02:00 AM                     That's a great idea of the moveable baffle panels to create that "baffle wall.." for this speaker assembly that you drew up! Real big trick is to have the speakers as close as possible to the backside of the screen - almost touching - so the sound, esp the HF's, definitely penetrates through the screen without hardly any reflection from the backside of the screen. Then,still use the fly curtain behind all of this.. Good luck - Monte  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 04-08-2009 06:30 AM                     It will work...you will need to re-EQ afterwards...you will be amazed at the bass improvement. We set up some Altec A4s similarly where thw wings folded in. You will want to make sure the wings are RIGID when opened to avoid rattles. Keep the mid-stage traveler...not just for sound but for light too. BTW...if you have access to Altec A4s...you'd be amazed at how much better they do than direct radiator type speakers in this environment...keeping things horn loaded down to 80Hz keeps most of the sound going forward to begin with. JBL's PD5000 series speakers also do well (PD5322). Steve  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 04-08-2009 10:32 AM                       Steve is on the money as he usually is.  |  IP: Logged Kenneth Wuepper Phenomenal Film Handler Posts: 1026 From: Saginaw, MI, USA Registered: Feb 2002 posted 04-08-2009 11:53 AM                     Randy, Those are very fine animations you have created. I wonder where you get the invisible stage hands who are opening the wing panels? You might find this page interesting as it is an Altec catalog from the early days. We have one of those A-2 systems and it still works great. We did make it Bi-Amp though. http://www.voiceofthetheatre.com/vottcat.1945.th.htm The wing panels are very heavily reinforced and they have little or no resonance. The Altec panels are carriage bolted to the main box. Hope this helps. KEN  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 04-08-2009 02:08 PM                     I made the animations with Blender 3-D. It took a couple of hours to do the modeling and animation and about 15 minutes to render to a file. I tweaked them up and compressed them for the internet with Final Cut Studio. The whole process was done in an evening's work. I plan to make the wing's like Hollywood flats. I'll make frames out of 1-by lumber and skin them with 1/4" luaun. They'll be glued and screwed to keep them from vibrating. There'll be a couple of runners made from 2X4 to attach the wings to the cart and I plan to put brackets on the back so you can use a piece of wood as a brace to lock them all together. (Kind of like the way you keep an old barn door shut.) I'll paint everything black, as will the carts be painted black. I only colored them like wood in the animation because I wanted the viewer to be able to see what is speaker cart and what is baffle panel. Should I cover them with insulation on the front or just leave them bare wood, painted black? As they are set right now, the speakers are just about 8 feet apart. That's good because it will be cheaper to make from 4X8 plywood. Just zip a sheet in half, vertically. How tall do you think the wing panels should be? Can I make them out of single sheets of plywood and center the 8 foot tall panels around the speakers? Or, should they go all the way to the floor? Yes, I will put a plywood panel on the center cart to block the open hole. Again, I left it out for clarity. I would LOVE to get new speakers but I practically have to sell my mother to get what I've got! (JK ) I'm going to have to make due. The center speaker is not the same as the stage left and right. The left and right are JBL 4675C. The center is different. If forget the model# but it is the previous version with the longer horn, shaped more like a giant trumpet. (Don't yell at me! I tried to convince them. They didn't listen.) The bright side is that the center speaker is damaged and will need to be replaced. When it is replaced it will have to be a 4675. Then I can push all three speakers up close to the screen. For 10 years, I have been bitching and screaming about getting a new sound system. Several occasions I have pitched the idea but it always fell through the cracks. Seems like I have a half decent chance this time. Some of you may already know that I have a real cobbled-together setup here. I'm trying to get a USL JSD-80 to replace the old Smart Mod IIB and all new amps. I'm trying to get them to get the Dolby Digital reader to go along with. Let's keep our fingers crossed. Eh?  |  IP: Logged Kenneth Wuepper Phenomenal Film Handler Posts: 1026 From: Saginaw, MI, USA Registered: Feb 2002 posted 04-08-2009 04:32 PM                     Randy, Perhaps you should consider making the panels from a non-laminated material like OSB. There is very little resonance to it and it does not de-laminate when flexed or subjected to humidity changes like plywood. Marine plywood is very expensive but has no voids within the lamination. The Altec bracing is more like 2 x 4 and is all bolted together where it meets the paneling. Something like a piano hinge on steroids would work best for the swinging panel attachments. If you are going to store these things around people, you might consider having the panels swing in front of the speakers and make them safer from tampering while they are not in use. KEN  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 04-08-2009 05:48 PM                     Funny you should mention... When we first bought those speakers I was concerned about the cones getting busted when they are stored around the shop. I kept saying that we should get grills for the front. When they asked me the price I told them it would be about $20 per speaker. At 6 speakers it came out to $120. They wouldn't hear of it! It was barely a year later when the speakers were stored in the shop and somebody was pushing a big piece of scenery around the shop when we had our first accident. It was the corner of a piece of plywood that went through one of the cones. It put a nice big gash right through the middle! The very next Monday I was told to order grills for the front of the speakers. It ended up costing the $120 for the grills PLUS the cost of a replacement speaker! Stuff like this is a near-daily occurrence, sometimes. I like the idea of folding the panels around the front. I'll think about it. You're right about the OSB. I only thought about luaun because of the weight. I think I'll use your idea.  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 04-08-2009 06:22 PM                     Hi Randy I had the same issue in a cinema that had to be setup with a stage too. The speaker are (not self) suspended. The sound was poor so we built wings with 2.5" acoustic damper on it up to the horns. The same around the subwoofers, just the wings were larger. I had +6dB on subwoofers response. The sound back from the screen did not jump on the back wall (many meters behind) anymore. The result was a very soft and clean sound, much much better than without the wings. So: do it. I think that the wings should be very solid. I don't know if you can build something strong like the animation you did. Try to put something that can lock in place the wings once they're fully opened. Let us know Marco  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 04-08-2009 06:42 PM                        I use a variation on the JBL 4675 for rentals; same except for a shorter horn (not the 4670). Mine are built into rock & roll cases with the front cover split in the middle with piano hinges on the side; rollers on back! In use, you roll into place, lift upright, open the case and then secure with bungee cords across the back. The only thing that is a little wierd is that the LF is too close to the stage. Louis  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 04-09-2009 11:45 AM                     Thanks guys. Your encouragement means a lot. I think I'm going to push to get this done now, even before the sound system is upgraded. I'll try to get the wings made from OSB instead of thin plywood. I gather that you think the panels should go from the top of the horns all the way down to the floor. Correct? Weight is a consideration. Height is too. I have no problem going up as high as the top of the speaker is now but much higher than that and the panels stand to get hung up on overhead cables, curtains and scenery, etc. I'm thinking of making them about a foot off the floor as well. They may have to be pushed over and around obstacles. Sometimes they have to be pushed up and down on a ramp. Too close to the floor and they could run aground. I'm going to go pester the boss about it today. If, as you say, the system will need to be re-equalized, it would be silly to install a sound system, EQ it only have to redo it all when the panels are finally put in. Right?  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 04-09-2009 01:09 PM                     quote: Randy Stankey EQ it only have to redo it all when the panels are finally put in. Right? Yeppers. Just like completely finishing an install.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 04-09-2009 01:11 PM                        Right! If you are elevating the roller mounted speakers, make your frame in the form of a triangle with a wide base. Speakers are usually top heavy with the weight of the drive and horn. The wide base will hopefully prevent "upsetting" the speaker. Louis  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 04-09-2009 01:16 PM                     I had always envisioned that if you had a system like this, you would build a rigid wall with cutouts for the speakers, and then fly the wall. Maybe that's really naive? But wouldn't it be superior to fold-out walls on the speakers? --jhawk  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 04-09-2009 01:41 PM                        With respect to jhawk's point: Is there any reason not to fly the entire assembly (wall, speakers, screen)? I've not seen this done--is there a reason why it is not common practice? In the "legitimate" houses where I've run film, the speakers are either on wheels and can be rolled to the side when the screen is raised, or are permanently suspended from the ceiling above and in front of the screen. The issue with the speakers-on-wheels method is the space that they take up when stored, and the issue with the speakers-suspended-from-ceiling method is bad sound.  |  IP: Logged

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