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Author Topic: Alternatives to Curtains Ian Bailey Master Film Handler Posts: 317 From: Nambucca Heads, Australia Registered: Jun 2003 posted 11-07-2006 01:14 AM                     Hi I need to resolve a problem I have in one auditorium which has way too much echo.I know this is partly due to poor design which we will be able to overcome and also due to having nothing on the side walls. i want to stay away from curtains as the cost of fire-proofing(which is law down here) is VERY costly!! I have been shown a piece of material that i was told could be glued directly to the wall(like wallpaper) which would help accoustics but have not been able to source a supplier. Could you guys give me some ideas on what you do for this problem? Cheers Ian  |  IP: Logged Cameron Glendinning Jedi Master Film Handler Posts: 845 From: West Ryde, Sydney, NSW Australia Registered: Dec 2005 posted 11-07-2006 02:17 AM                     Ok Ian, The cheapest way to fix your problem is to stop it in the first place! thin fabric doesnt do much compared with modifing the speakers positioning as not to excite the reverberation. How are your stage horns angled? what is the shape of the cinema? what brand loudspeakers. Ideally you want the left and right horns to be angled or steped inwards located 2/3 up the screen aiming down to the middle of the seating, the sound is broken up by the audience and seating before it gets a chance to bounce around the side or back walls inside the room. Typical coverage from these horns found in cinema is 90 x 40. tighter control can be gained by changing to a 60 x 40 horn on your stage speakers. This is very cheap (ie hundreds $) compared to wall coverings. I have found that getting the speakers positioning perfect in poor acoustic rooms can have dramatic positive effect. I have more to say but would like more detail about the room.  |  IP: Logged John Wilson Film God Posts: 5438 From: Sydney, Australia. Registered: Dec 1999 posted 11-07-2006 03:52 AM                     Hi Ian Indeed. Cameron was instrumental in removing the dreaded echo from the carved up Valhalla. If he can do that, maybe shout him a trip to NH to see what can be done. It may work out much cheaper in the long run to do that than expensive accoustic dampeners. John  |  IP: Logged Ian Bailey Master Film Handler Posts: 317 From: Nambucca Heads, Australia Registered: Jun 2003 posted 11-07-2006 06:01 AM                     Cameron, This is only a new site we recently took over so I don't have all the information to give you at the moment. I will be there over the next 2 days to help with the service of the equipment so can have a closer look then. The problem the way I see it is that if you stand in the middle of the empty auditorium and clap your hands together loudly it sounds like you are in a cave!!! Not sure if your fix will resolve this. I think the major part of the problem is the bulk heads that run down each side wall.They are about half way down the wall and are open at the top. Cheers Ian  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 11-07-2006 08:27 AM                     Ian, The clapping of hands method (one I use) confirms WHY there is a problem but Cameron is dead right...step one is to direct the sound at ones ears and not at the confirmed echoy walls. When you clap from the audience perspective you are NOT simulating the sound from the speaker's origination. For instance, you can have side-wall slap easily picked off by the clap of the hand but now look at the path the audio must take to hit the side wall and then slap back and forth...it is totally different. The back wall is likely the next stop for the sound (think like a pool ball bouncing around on the cushions). So if your rear wall is also hard the reverb/echo may be worse or better depending the path taken and how distant (time wise) the echo is from the direct source. Step one though is to get the sound aimed at the ears and not at the hard surfaces. I normally advocate horn-loaded systems for rooms like this too. In my opinion, you will never achieve the quality level of having a properly treated room but if one can't affect the walls for architectural or historical reasons, then job one is to keep the sound off those surfaces in the first place.  |  IP: Logged Dave Williams Wet nipple scene Posts: 1836 From: Salt Lake City, UT, USA Registered: Jan 2000 posted 11-08-2006 02:18 AM                        For fear that I will be strung up by my toes for saying so, but pointing your speakers around isn't going to do you any good. The first rule of sound is that sound travels. Sound will not stop when it has reached the last patrons ear. It will continue to travel, albeit now in a vastly mucked up way. Pointing your speakers in the right way is definately the correct thing to do, but too many people rely on this as a solution to a problem that it cannot be a solution to. Pointing your speakers in the right direction without taking care of your acoustical balance only assures you that you are going to have to do this again. If you don't take care of acoustics first, pointing them will only change the mucked up sound to a completely different mucked up sound. It took years for a local stage theater owner to understand that, waiting about six years after opening the doors before actually discovering that pointing the speakers didn't do anything but change the sound from muck one to muck two. Only by making alterations to control the acoustical response and THEN POINTING your speakers, and of course a proper EQ, will you find a true solution. Don't waste time fixing something that you are just going to have to refix once you actually fix it. Or something like that. Ciao  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 11-08-2006 09:46 AM                     Dave, I don't think anyone is disagreeing with you...in fact my statement above yours stated that mere pointing the speakers will not make the room right. However, by directing the sound energy to the audience you will effectively lower the output SPL from the speakers since what they will hear is more of a direct path. By lowering the energy, and then taking into account the absorption of the sound introduced by the seats/people...what reflects off will be a notably reduced level that must continue to follow the inverse-square rule before it hits its first hard surface to reflect...continuing to attenuate on its travel to either another surface or an ear. It is this non-direct sound that one is trying to minimize by aiming the speaker. Note too I recommended horn-loaded systems to direct the entire bandwidth of the speaker to keep as much sound off the room walls as possible for as long as possible. To claim this will make no difference or no improvement is just plain wrong. I've done it many, many times. Take a trip to Colonial Williamsburg...the Kimball theatre, for Historic reasons could not have anything modern visible and was to look as period as possible. The surrounds are not visible either. Some DSP and bass management were required to bring that system into line. The VP of the foundation in charge of the theatre declared it sounded better than most of the cinemas he had been to (I'm not sure if that was praise for the results or a condimnation of most theatres!). In truth, it sounds much BETTER than it did but not what I would consider ideal or even correct. None-the-less it ran a premier of NEW WORLD and everyone was very pleased with it. For the record, I DID use Altec A-5s with Mantaray horns (they are the best, period) for the stage speakers. The surrounds were EAW. The Cinema system shares the subwoofers with the PA system and I recall they are EVs. Steve  |  IP: Logged Bruce Hansen Jedi Master Film Handler Posts: 847 From: Stone Mountain, GA, USA Registered: Dec 1999 posted 11-08-2006 07:00 PM                     How about putting rug on the walls, if you can find some that is flame proof. Or build a 2X4 wall in front of the existing wall, fill it with insolation, then put burlap over it.  |  IP: Logged Cameron Glendinning Jedi Master Film Handler Posts: 845 From: West Ryde, Sydney, NSW Australia Registered: Dec 2005 posted 11-09-2006 02:00 AM                     THX acoustics would be very nice! Don't get me wrong Dave, I do think its worth the money if you can afford it! Thin material glued to the wall is not the same as dense curtains that are pleated and hung a few inches from the wall or acoustic panels made from fiberglass wrapped in a woolen material or rug or uneven 3d panels or walls that are not parralel, these would work far better. From my own experience, I tend to find that using more directional horn loaded speakers than usually found in cinemas, combined with a backstage acoustic treatment. Ie Black tissuefaced fiberglass ductliner (3.2 kg per squ metre) attached to the back wall behind the screen. Quality surround speakers that are steeply angled towards the ear, is also very important! I came up with this approach for an old art deco theatres so that the look would not change but clear audio could be heard. The better the acoustics the less important the speaker positioning. All of the above, material costs less than $2000, playing with the existing gear is free! I also would suggest wings to your speakers for a better bass responce. If angled between 3 and 7 degrees it would reduce flutter echo. When you have more details I would love to think this out. Cheers Cameron  |  IP: Logged Ian Bailey Master Film Handler Posts: 317 From: Nambucca Heads, Australia Registered: Jun 2003 posted 11-10-2006 02:08 AM                     Cameron/Steve OK now I understand,pretty simple really. Cameron I didn't get a chance to get behind the screen but if the surrounds are anything to go by I'm a bit worried what might be behind there.I'm doing a full refurb of this one hopefully early next year and I know where there are some excellent stage speakers and some Krix surrounds so it would be great to have a chat about this before the install. The sound gear was QSC amps and DTS6AD..........which didn't sound too bad after the EQ was done....but I am getting old and deaf!!! Cheers Ian  |  IP: Logged

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