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Author Topic: How Do Drive In Cinemas Work? Dave Bird Jedi Master Film Handler Posts: 777 From: Perth, Ontario, Canada Registered: Jun 2000 posted 03-19-2007 10:09 AM                        I've seen a fair number of 3K installs here in Canada, mainly because the drive-ins that remain are in small-town, even rural locations without access to 3-ph power. Screens are generally 60 footers, give or take. Our screen currently has 2K for an 80 footer (we do not run this place YET), which I'll be looking to "rectify". Out in the "boonies", it actually looks okay for the many animated and FLAT (of all things) pictures. Darker films and scope not so much. I think our eye "tricks" us on screens that large into seeing more light than is actually there. I rather think the scope lense must need replacement and we'll be installing a new lamp. Luckily, in this location 3 ph. runs right behind the booth. More updates as the season progresses....  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 03-30-2007 06:59 PM                     This is a Drive-In that I pull sunday night shifts at on occasion when they begin them each season. When this place opens up, it's usually just on weekends until the weather breaks to bring in a good Sunday crowd, then it'll do Thurs thru Sundays until the weather breaks in being vold again (since there are no car heaters, let alone no poles to talk about..) (little background of mine: I started this career of mine at an ozoner, and was doing ozone work for a good 12 yrs in all - the last in 1984 until I went to this ozoner above 2 yrs ago..from on-call tech to a regular one night a week shift) Sadly, going back to sound issues: I just came from this place doing a sound tune-up for the season (everything was in order) and putting together the two movies that they will open up, but there is one thing that the people out in their cars duely miss than if they go to a hardtop-and that is DISCRETE sound. Granted, this place as well as other drive-ins around the world contain FM stereo sound, but the bit misfortunate is that the pickup is all optical and raw stereo - raw being that the optical pickups are picking up the L/R tracks from the film and shooting it directly out to the cars from the preamp card, or amplifier to the FM transmitter (and AM transmitter as well if a ozoner has dual broadcasts) without any form of processing - Thus, you do have stereo, but when dialog kicks in, it's coming out of both speakers making the voice tracks much louder than the individual left/right information and losing the stereo effect where the stereo effect is more prominant in an hardtop with discrete channeled stereo sound. Too bad, (as far as I know of now, unless someone can enlighten me on tips or mods..) that there isn't a way to 'trim' down the dialog to balance with the L/R information and have really good stereo out in the fields.  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 03-30-2007 08:28 PM                        "Too bad, (as far as I know of now, unless someone can enlighten me on tips or mods..) that there isn't a way to 'trim' down the dialog to balance with the L/R information and have really good stereo out in the fields. " There is! You can use a regular Cinema Processor connected to a mixer and sent the Left and Right to thier respective Channels and send the Center to both left and right and use the faders on the mixer to properly set the levels. You will also gain the noise reduction that you lose when you send raw Lt and Rt signals unprocessed.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 03-30-2007 08:48 PM                     Very Good, and I do thank you for this much needed info! It'd be quite easy to hook up with your explanations above. Thx again - Monte  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 03-31-2007 10:48 AM                     Mixing the output of a matrixed source can cause strange pumping sounds The Smart MOD2b Drive In processor works well and provides a l/r out for the fm and two mono outs one for am and one for a field speaker amp  |  IP: Logged Jack Ondracek Film God Posts: 2348 From: Port Orchard, WA, USA Registered: Oct 2002 posted 03-31-2007 11:41 AM                        Monte, If the owners aren't interested in buying a cinema processor, perhaps you can kick up the compression a bit. A comp/limiter/expander, such as those made by Symetrix, could tame some of those level differences, and maybe attempt a little downward expansion during quieter passages. What kind of transmitter are you using? Interesting that you're noticing dominance in dialogue. I'd figured that unprocessed Dolby tracks were too compressed as they were. You'd really notice it in an outdoor scene, like if someone was talking at a busy crosswalk. In the places I worked with, the traffic/ambient noise was uncomfortably close to the actors' audio, making the mix sound unreal. In the end, I think you'll probably find you WANT a certain amount of dynamic reduction. Automotive FM systems aren't much good over a 40dB range, if that. Add passenger chatting and the squished broadcast audio they're used to hearing, and your unprocessed FM can sound unnatural and hard to follow.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 03-31-2007 02:53 PM                        You're right about "hot" dialog. I decode the SR and then(using EQ) dump the mid-band where speech lives (300-2500 Hz). You will then, in effect, lessen the mono speech, while improving the bass and treble where STEREO lives. Remember this is a RATIO; a little bit will help a lot; easily overdone! Louis  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 03-31-2007 10:45 PM                     quote: Jack Ondracek Interesting that you're noticing dominance in dialogue. I cheated - while walking around out in the yard, I used a pocket FM stereo gear listening with a good pair of Sennheiser fones. I wanted to hear what a hardtop tekkie should be hearing when doing loop tests. This is when I noticed that the voice track was more predominant than the L/R information - then thinking, that with the voice is coming out of both channels, it was increasing that section of the presentation and drowning out the L/R music/effects that really makes a stereo presentation noticable. For, when I've gone out to drive-ins for movies that broadcast in FM stereo, something just wasn't there .... didn't sound too well .. and this was the reason - using unprocessed stereo optical tracks.  |  IP: Logged Jon Paul Johns Film Handler Posts: 18 From: Oklahoma city,Oklahoma/United States Registered: Nov 2005 posted 04-06-2007 11:52 AM                     We have a drive-in here in Oklahoma City, the Winchester Drive-In and I have just upgraded the sound system with a Dolby CP65, Kelmar Digital/Analog basement reader for a RCA, DTS-6 SYSTEM, And soon if I can ever find a Dolby digital processor a DA20 or a CP500 but here is my problem I need a mixer to output left, right stereo for my FM SKY MONITOR and a mono for my field speakers & AM transmitter Phase II model. I like Behringer rack mount mixers but there is so many different kinds if some one could provide me with the specs or a model number. Jon  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 04-06-2007 07:29 PM                       No mixer necessary. On a CP-65, you can just use the Lt Rt outputs on TB2 to feed the FM. You don't get NR, but it's quick and easy and I'm not sure it makes that much difference anyway in an outdoor environment. The H/I output on TB3 is a summed mono and will take care of the monaural feeds.  |  IP: Logged Jon Paul Johns Film Handler Posts: 18 From: Oklahoma city,Oklahoma/United States Registered: Nov 2005 posted 04-06-2007 08:16 PM                     Tim, your right but with digital the left goes hard left & right goes hard right and center is mostly dialog so with a mixer you can correctly mix the left and right output.  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 04-06-2007 11:18 PM                       Sorry, Jon, I misread your post. I thought you were having trouble now with the present setup. For digital, you could pad the channel outputs with resistors, attenuating the L and R channels a bit more so as not to overpower the dialogue when everything gets added together. If you used a stereo mixer, just keep L on L, and R on R, and place the C channel pan pot midway. Then adjust L and R in tandem to get the dialogue where you want it. Don't the Behringers do this?  |  IP: Logged Jon Paul Johns Film Handler Posts: 18 From: Oklahoma city,Oklahoma/United States Registered: Nov 2005 posted 04-08-2007 04:33 PM                     Tim, I don’t have a Behringer yet, I am trying to find one but I do not know witch one to get they make so many different models. I need one with two left inputs; two rights inputs, two mono inputs, one left output, one right output and one mono output. Tim, if I were to use resistors how would I keep left and right separated when I add the center channel? Jon  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 04-08-2007 05:32 PM                     the hearing impaired output is a summed signal and could be used as a monoural feed If not I would build a small matrix to sum the signals as required but I would tend not to attempt summing a output of a matrix as there will be some pumping present  |  IP: Logged Jack Ondracek Film God Posts: 2348 From: Port Orchard, WA, USA Registered: Oct 2002 posted 04-08-2007 07:22 PM                        quote: Tim Reed If you used a stereo mixer, just keep L on L, and R on R, and place the C channel pan pot midway. Then adjust L and R in tandem to get the dialogue where you want it. Don't the Behringers do this? Yes they do. Unless you know what you're doing, building the pads, and then the passive voltage divider you'd need to mix the mono sum into the l & r would be beyond most owners interest and ability. You'd probably have to amplify the result, to compensate for pad losses, THEN mono-sum the whole thing for his speakers & AM (possibly also needing another line amp). Technically, you're correct. You want left to left, right to right, and center to feed both. However, adding a passive pot to the center channel will lower stereo separation because you're effectively feeding one channel to another through the pot. Use a mixer with active inputs to isolate the channels. Most do, but you need to check. There are scads of them out there. I use a Behringer, because it's inexpensive, has good specs and is inexpensive. I don't much need bulletproof pots, because they rarely (if ever) need touching. I use a little Behringer UBB802 (about $60) that has enough channels for me to also add l/r surrounds AND the sub channel (also mono). You can debate whether those channels add to the mix, but that's what I do here, and it sounds great. The controls make balancing center dialog to the other channels a snap, so that's not much of a problem, either. The mixers are available from online sources, like "Musician's Friend". Looks like the 802 is now called the Behringer 'Xenix 802'. This mixer also has an isolated headphone output that you can mono-sum for your speaker system. You should be able to tap that line for the AM transmitter, because it has its own input pot. I would have gone with a rack mixer, but I didn't want the controls out where they could get bumped (and changed) accidentally. These little guys mounted in the back of my rack... set and forget. If I had put in a rack-mount, I probably would have added a front cover.  |  IP: Logged

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