Film-Tech Forum ARCHIVE: How Do Drive In Cinemas Work?

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Posted by Demetris Thoupis (Member # 833) on 03-12-2007, 02:08 AM:

I have never seen in real a Drive in Cinema. All I have seen is from the photos in hear. I was wondering what are the main differences between a closed type cinema and a drive in Cinema. Mainly it has to be with the sound right? If someone could enlighten me with the way a Drive-in cinema works? What material is it used for screen? Are speakers placed behind screen or at the side and also in the cars?
Best Regards

Demetris Thoupis

Posted by Christos Mitsakis (Member # 143) on 03-12-2007, 06:05 AM:

No Drive Ins in Cyprus? Dimitri you don't miss much.

No offence to our US friends but Drive In cinemas in Greece were
99% identified with porn movies and have declined since the widespread of VHS at the end of '80s.

Screens were mostly made from metal sheets and rarely of concrete, with unacceptable or passable carbon ark projection.

Actually the cinema was a large parking lot with the booth close to the screen for obvious reasons. At each car position there was a post with a cheap loudspeaker enclosure hanging so that you can pull it inside the car during the show.

Modern Drive Ins use stereo FM transmitters so you can tune the car's radio receiver to the cinema's freq and enjoy stereo sound.
I understand in US it is a cultural phenomenon especially during the '60s (please correct me for any historical errors).
C.

Posted by Stephen Furley (Member # 1277) on 03-12-2007, 07:15 AM:

So what if your car doesn't have a radio; are the post-mounted speakers still available as well? Or do you have to take a portable radio?

As far as I know we've never had a permanent drive-in in the UK, though I think there were a few temporary ones set up long ago. The possible reasons for this were discussed in a thread a couple of years ago. We do have a few outdoor screenings in various parks etc. each year, or at least we did, I haven't heard of any for the last couple of years, but again, these are temporary set-ups installed just for one show. Searing is on the ground, or deck chairs; there are no cars involved.

I think the question I would ask about drive-ins would be 'why?' Personally, the less time I could spend sitting in a car, the better. If you want to watch the film then there must be better places to see it, and if you're going for other reasons then why not go somewhere else, where there isn't a film showing?

There was a Pathé Pictorial about one that opened in Italy, Rome I think, sometime around 1960, which predicted that we would all soon be going to these places, but it never happened. I've got a slightly faded Super-8 print of this film somewhere; a rare example of Super-8 with an optical track.

Posted by Demetris Thoupis (Member # 833) on 03-12-2007, 09:12 AM:

I am more concerned on the technical part of it. I mean how do you distribute 1 single audio to like 200 pole standing speakers? Were/are these speakers 100V line system ones? From what I understand, the modern days which use FM transmiters need to have a "clean" frequency. How do you set the limit of the transmitter? Is the frequency preset by an organisation or something or do you just put one out of your head which is "clean"? How do you inform the viewers on which frequency to tune their radios in order to hear the film? Anyway these are some of my questions with plenty more to come although I dare not ask all at once in case someone answers them anyway!
Best Regards

Demetris

Posted by Tim Reed (Member # 137) on 03-12-2007, 09:24 AM:

Drive-in theatres have reverted back to a family atmosphere in this country. Many new drive-ins have been built over the last 10 years, and FT-er Justin West owns one of these new-builds.

In the late 70s through much of the 80s, however, many drive-ins had to resort to running porn to stay in business - particularly for many locations that ran during the cold winter months.

Radio sound raised the quality-level for drive-ins somewhat, and patrons without radios in their cars can usually rent a portable unit from the theatre.

Screen illumination has always been a problem in drive-ins.

Car culture is also very big in the US, so going somewhere and hanging out in your car is no problem. I may be guessing, but I think our cars are generally bigger than common European models (our imports notwithstanding), which may have a bearing on the comfort level.

For more info on the technical specifics of drive-ins (including in-car speaker systems), visit my old website: Drive-In Theatre Workshop.

Posted by Barry Floyd (Member # 385) on 03-12-2007, 10:24 AM:

I own one of the "new build" drive-in theatres here in Tennessee - ours opening up for the first time in August of 2003.

Technically speaking, from what I've seen, other than the size of the lamp, screens and the way the audio is sent to the patrons, there's really not much different the way we do it as opposed to the local indoor multiplex.

We have a twin screen drive-in. In booth No. 1, we have a Simplex XL mounted on top of a Simplex SH1020 soundhead with a Component Engineering LED reverse scan reader. A 4kw Xenex II lamphouse rides on the back, shooting the picture 350 feet from the booth to a 25 x 60 foot screen through new Schnieder lenses. The sound is processed through a SMART MOD II DIT (Drive-In Theatre) sound processor, then fed directly to a Broadcast Warehouse TX-5 FM transmitter. Screen 1 broadcasts on 87.9 FM at a little less than 0.1 watt of broadcasting power.
The booth in Screen 2 is virtually identical with the exception of the projector head which is an old Brekert BX-60 on an RCA 9030 soundhead.
Both booths have a 3 deck Strong AP3 platter system.

I have some booth photos and screen construction photos on our website HERE

Rodeo Jack is the current reigning "King of Technical Toys" as
far as US drive-ins go. I'm hoping he'll post some of his booth photos - unbelievable stuff! [thumbsup]

Posted by Dave Macaulay (Member # 813) on 03-12-2007, 10:37 AM:

I don't know of any drive-ins with post speakers still in use.
I don't think you can buy a car without a radio, in 1976 or so I had to pay extra to have the radio deleted in a Honda Civic.
The speaker audio went out as 70V and each speaker had a small transformer inside the case.
The current FM transmitters are very low power and operate under special low power licenses. You just need to pick a frequency with no local signal to avoid interference on the lot, the signal from your transmitter doesn't reach far enough to cause external interference. The old AM systems fed the signal to the lot and there was a wire on the post that you hung over or wrapped around your car antenna, that's about all I recall. I don't think they radiated from a central antenna like today's FM system.

Posted by Jack Ondracek (Member # 1466) on 03-12-2007, 12:01 PM:

There are pictures of our booth HERE.

As Barry says, it goes a lot further than most drive-ins would probably go... but we live at our place and this is what we do. I needed a playroom of my own, and this kind of became it.

Generally speaking, the major difference between indoor and outdoor projection systems is the sound equipment. There's no practical way for a drive-in to use stage and surround speakers, so our audio goes into window speakers or low power radio transmitters. Drive-ins also tend to need the higher-power lamphouses, whereby many indoor houses can get by with lower-wattage versions. Otherwise, much of the equipment in a typical indoor booth can be used at a drive-in.

Re Stephen's question about what to do if no radio: Portable radios work as well as installed car radios. Our customers can bring their "boom-boxes" with them, and frequently do. We keep around 10 little portables, which we rent to those few who manage to come out here without a functioning FM radio.

As Dave suggests, there aren't many drive-ins left that have functioning speaker systems. Here's one that has both speakers and FM radio. Other than the removal of the post lights, the speaker system is virtually unchanged since it was installed in 1952.

Prior to the current popularity of FM for transmitting drive-in sound, AM was widely used. The signal was sent out to the cars by just about every method imaginable. The first I saw was a system whereby a "leaky coax" was buried under the ramps. The signal was pretty weak... not much got outside of the drive-in. I saw one installation where a "jammer transmitter" was wired around the fence line. It did a pretty good job of messing up what little signal did get outside the theatre.

Some AM systems used various free-radiating antenna schemes. Others used carrier-current, wired through the existing speaker wiring and received either directly or through a clip-on antenna wire. One of those "clip-on" methods, the "Cine-Fi" system is still used at a 6-screen drive-in in my area.

As far as I know, just about everyone is gravitating to FM. There are still a few drive-ins that only have window speakers... but most have added some form of radio sound. Depending on how you choose to feed the "transmitter", FM allows you to take your sound up to the limits of your customers' radios. Maintenance is extremely low, compared to an outdoor speaker system.

Drive-in operators have also connected up their transmitters just about every way you could imagine. On one side, I've seen monaural systems that were connected to existing, "low-fi" speaker systems. On the other hand, you can use good theatre processing systems with very good results. One thing is clear about FM... it's as good as what you feed it. If you have problems before the transmitter, your customers will hear it all. If your sound is clean going in, they'll hear that, too.

As for your specific questions: Dave describes the speaker systems pretty well. In many ways, they're just glorified public-address systems... similar to the background music system in a grocery store or shopping center, except for the kind of speaker that's used. Except for the novelty, I wouldn't go to the expense to build a speaker system today. Your customers are able to compare your sound to what they can hear on their radio. By today's standards, no 4-inch drive-in speaker will ever sound all that great.

As for the transmitter: You want the cleanest spot on the dial you can find. A frequency with nothing on it takes very little signal to cover your field. Frequencies with other stations on them can take much more. If your signal interferes with a nearby station, you risk bringing unwanted attention upon yourself!

Most transmitters use circuitry that no longer depends on the use of crystals. You can usually change the frequency yourself. Some can be changed from the front panel. Others require you to take the top off to get to the switches. The operating manual will tell you how to do this.

Most, but not all transmitters have power controls on them somewhere. If you buy one, that will be part of its specifications.

Some models will also include stereo generators and a wideband compressor/limiter. The internal limiter may not make you sound like the local commercial station, but it will keep your levels somewhat consistent. If you don't get one with internal limiting, you'll need to add something on the outside.

How to legally use low power FM varies by country. You'll have to check in your area to see what you can do.

Transmitting equipment is available through Broadcast Warehouse, with outlets in several countries, Decade, out of Canada, and Ramsey Electronics. You can usually find FM transmitters on Ebay, but I don't know if they're any good.

Several companies make FM modulators, generally intended for use in cable TV systems, but adaptable for drive-in use. I saw a couple of Drake models in New York recently, and they sounded pretty decent.

Posted by Brad Miller (Member # 2) on 03-12-2007, 02:36 PM:

Oh no, no, no, no, no, no. THIS is a drive in! [thumbsup]

Posted by Jack Ondracek (Member # 1466) on 03-12-2007, 02:40 PM:

It sure was!... and I sure wish I had been able to see it when it was running.

Unfortunately, it was on the other side of the state, and I think I may have been too young to be admitted!

I've never been able to imagine the time and care it would take to clean the optics at that place. It doesn't look like there was any obvious effort to keep the dust out, though with the subject matter, the customers may not have noticed! [Eek!]

Posted by Wayne Keyser (Member # 2420) on 03-12-2007, 09:10 PM:

"Personally, the less time I could spend sitting in a car, the better. If you want to watch the film then there must be better places to see it, and if you're going for other reasons then why not go somewhere else, where there isn't a film showing?"

Then you never got together with your college buds on a "can't get a date" Saturday night, hid a six-pack (each) under a blanket, and laughed yourself half to death over a triple bill like JACKSON COUNTY JAIL, POM-POM GIRLS and HOLLYWOOD BOULEVARD. And the funniest thing of all was the intermission trailer: "Enjoy movies in your car, smoke if you like!" ("Yeah, right! Pass that joint over here, man!")

Posted by Tim Reed (Member # 137) on 03-12-2007, 09:50 PM:

quote:
the funniest thing of all was the intermission trailer: "Enjoy movies in your car, smoke if you like!"

But, I digress...

quote: Jack Ondracek
I've never been able to imagine the time and care it would take to clean the optics at that place.

The one I saw was spotless. The dome housing the mirrors was a high-priority maintenance item for them. It was also humidity controlled.

Posted by Chad M Calpito (Member # 3736) on 03-12-2007, 10:30 PM:

Hey, Brad, I would have to agree with you. That drive-in was cool looking. I've never seen anything like that before.

Posted by Frank Angel (Member # 248) on 03-13-2007, 03:14 AM:

So, the big threat was TV and DIs had the lure of the giant screen. What were these guys thinking -- so you build a DI that has what looks like small TV screens. Pretty counter-intuitive, no? Probably the idea was a great challenge, and they go caught up in just making it work (which as anyone can see was a magnificent feat in and of itself), but once you get past the gee-wiz ma, look what I built, you've gotta admit it was a lame idea. Here's a case of great execution....bad concept.

But like very one, I sure would have loved to see that in operation.

Posted by Tim Reed (Member # 137) on 03-13-2007, 08:37 AM:

One of the ideas behind the design was that it couldn't be seen from outside the perimeter of the theatre (which, in the 70s, turned out to be perfect for porn, although that wasn't the original purpose).

The field size of the image was about the same as a normal drive-in setting; the picture filled a good portion of the windshield. Because people in the backseat could easily see the picture with the screen right in front of their car, this made grading ramps unnecessary - a significant cost savings.

These two points alone allowed for the inexpensive construction of a drive-in theatre in almost any location - in the country OR the city.

Pretty good concepts.

Posted by Frank Angel (Member # 248) on 03-13-2007, 09:27 AM:

I see what you mean Tim, but even though this all works out theoretically, I mean, like you say, the apparant size of the screen is about what most people would actually see at a drive-in relative to distance and how much of the screen takes up your field of vision, but I think the impact of the huge drive-in screen is its real calling-card. It's the wow factor rather than the actual relative size, just like you can sit two feet from a 19in tv set, but walk into a room that has a 52in flat panel wall screen and the latter is much more impressive than the former.

As for porn not being seen from the road, I wish I could find someone who actually put in one of the super directional hi-gain DI screens which I only read about. The claim was that unless you were sitting pretty much on axis, the fall-off was so severe that you couldn't see the image from the road. A lot of super engineering going on just to stop people from seeing a little flesh. Show some tit and nipple and people want to tear the place down....show that tit and nipple getting sawed off with a buzz saw just before the beheading with a meat cleaver in a slasher-horror film....no problem. Strange creatures these humans --- so fond of fig leaves.

Posted by Floyd Justin Newton (Member # 1316) on 03-13-2007, 10:33 AM:

Frank-- Ain't that the truth ! [Confused]

Posted by Scott D. Neff (Member # 185) on 03-13-2007, 02:14 PM:

I've just started working for a drive-in company and don't know very much about what does and does not make a difference in the sound and presentation at a drive-in vs. a walk-in.

I see that Jack's drive-in is equipped with all the digital systems you'd find at a walk-in. Does digital sound translate over the FM broadcasters well enough to really wow somebody in their car?

Also, as far as lamphouses go, we're using old old ORC lamphouses, with what I GUESS is 4000 watt xenons. I have NO idea what the size of our screens are, or the length of our throw. I guess I'm asking just for an example of what other drive-ins might use to properly illuminate their screen, especially if there is a lot of ambient light from neighboring businesses and streets.

Posted by John Wilson (Member # 269) on 03-13-2007, 02:39 PM:

The throw's not that important...only the area of the screen to guage the lamp size requirement. Also needed to take into account is the ambient light etc from neighboring properties etc.

As far as 'naughty' movies being able to be seen from the roadway...when the Westline Drive-In was being built there was a letter to the editor of the local 'wrap-fish-in-it-on-the-day-it-comes-out' newspaper complaining that if ever there was screened a movie like 'Oh! Calcutta!" there would be a pile-up of cars a mile long on the highway.

Well, they must have had access to the schedule or the booker read this newspaper because within the first month of operation it was on the screen at the Westline. No pile-ups though...just lots of [sex]

on the screen and [sleep]

in the cars.

Posted by Tim Reed (Member # 137) on 03-13-2007, 04:50 PM:

What John said. I don't know how many times it has been stated on this forum, but THE THROW DOES NOT MATTER with regards to screen illumination! It just looks like it matters. The throw is only important in calculating lens focal lengths. I'll see postings elsewhere by theatre owners, and they consistently state the length of their throws when they ask about lamphouses and such. [Roll Eyes]

Scott, there are no properly-illuminated d/i screens! [Wink]

quote: Frank Angel
I wish I could find someone who actually put in one of the super directional hi-gain DI screens which I only read about.

There never were any, to my knowledge. But lots of tests were made over the years, with small sections of various prototypes.

Posted by Scott D. Neff (Member # 185) on 03-13-2007, 05:20 PM:

We seem to have installed a number of screens that are 36x76. Any suggestions for lamp power for one of those suckers?

Posted by Jack Ondracek (Member # 1466) on 03-13-2007, 05:25 PM:

quote: Scott D. Neff
I see that Jack's drive-in is equipped with all the digital systems you'd find at a walk-in. Does digital sound translate over the FM broadcasters well enough to really wow somebody in their car?

A properly-tuned SR system will take FM about to its limits. Many would say that's good enough. On the other hand, I like how the digital sounds. The highs are cleaner and there seems to be less distortion. You'd have to listen for yourself, and you'd have to have a very clean FM system... but I think it was worth it.

We weren't the first to do this... the second or third, I think. Since then, the Transit in Lockport, NY, and some of the new builds in Texas have installed digital. One database lists 9 or 10 of us that have the stuff.

quote: Scott D. Neff
We seem to have installed a number of screens that are 36x76. Any suggestions for lamp power for one of those suckers?

Yah... the biggest you can get!

The 7k bulbs may not get you up to industry standards, as far as light levels are concerned... but they look pretty darned good. 4k won't cut it. You need plenty of airflow through the lamphouse and a good reflector, but you can get a very good picture at a drive-in. If you have a good paint job, a hefty lamphouse and not much ambient light, nobody's going to walk up and complain about your picture. On the other hand, if the owner's using small bulbs with too many hours on a screen that looks more gray than white, then I guess you'd have some problems there!

I personally think those old 4k ORC lamphouses are among the two worst boxes a drive-in could have... the other one being those old, blue Christie CH40's. The Christie SLC series, as well as the Strongs, Xetrons and Big Skys blow those lamps out of the water. There sure seem to be a lot of them still around, though.

quote: Tim Reed
Scott, there are no properly-illuminated d/i screens!

How do you figure that, Tim? There are plenty of smaller drive-in screens that compare to indoor versions... at least as to square footage.

Posted by Tim Reed (Member # 137) on 03-13-2007, 07:00 PM:

By and large, d/i's are under-illuminated. Certainly, there are exceptions... note my [Wink]

Posted by Jack Ondracek (Member # 1466) on 03-13-2007, 07:24 PM:

Ahhhhh... how could I have missed that?! [Wink]

Posted by David Kilderry (Member # 142) on 03-14-2007, 06:14 AM:

Several generations of Australians grew up with drive-ins. We perhaps had more than any other country outside the USA with around 350 (did Canada have more???).

Australia has good climate, lots of land, a love of movies and a very strong car culture - all required for drive-ins to be successful.

Yes ours too fell to porn in the 1970's and 1980's but the ones that survive today, inlcluding ours, have not run porn for over 20 years. The families are back! We still love our cars and movies and whilst land is not cheap anymore, the climate seems better than ever!

GM-Holden, Ford and Chrysler all sell large V8 and 6 cylinder cars here (Ford and GM still make them here too). These large sedans are important in that families need space in a car to enjoy a movie. I can understand why they never expanded in Europe to the extent of here; in addition to high land value, and poor climate in northern countries, the cars were just too small.

We are all FM now, if we put speakers out on the ramps they would all be stolen, they are collectors items now. We have just a few out for display in the garden in front of the projection building.

Our screens are just over 80 ft wide and zinc-alum panel on a steel tower. They are painted pure white. We run 5,000 watt Strongs behind our Philips DP70 and Century DAW2. Light here is very good for a drive-in, especially compared to places I once worked at with 110 ft wide screens. With smaller fields these days enormous screens are just not required; good light is more important.

We still run pre-show and interval clocks.

Tim and John, you would not be surprised to hear how often I am asked "wow you are so far away from the screen, you must need powerful lamps" and that is from projectionists who should know better!

Drive-ins are part of Australian culture and a great way to experience a movie. For those that don't know, most people on warm nights sit on or outside their cars on deck chairs or blankets. Vans, 4wd's and wagons park backwards with the tailgate open and there are utes and convertibles too. We have seats outside our cafe with speakers for customers to listen to the movie, even the toilets have the sound piped through!

David

Posted by Dave Bird (Member # 490) on 03-14-2007, 11:11 PM:

Did Canada have more? I have a listing from 1988 that suggested that 250 existed at that time. There may have been a few more at some point, especially in the cities "back in the day". Drive-ins.com suggests that 80 are still open, I'd put it between 65-75 of them.

As for the climate, families showing up again and the fun? I'd have to agree based on what I've seen. These places may be more fun than ever, many have added screens, the movies are new (and appropriate) and though it's true that there's alot of competition for the entertainment dollar, it seems as though most of the "simple, good-old family fun" venues are gone. If you're looking to show the family the "way it was", then these 60-odd drive-ins(mainly in rural or vacation regions) are often the only game in town.

The "new build" phenomenon has even been seen here in a couple cases (Vancouver and Toronto).

Posted by Louis Bornwasser (Member # 3063) on 03-15-2007, 03:12 PM:

How much lamp?? Even a small screen should require 4500 watts or more. Light means you can open early; and that means DINNER! Most drive ins have the vertical angle (and sometimes the horizontal angle) wrong which costs about 80% of the light. It is not impossible to have in excess of 16 ft/lamberts if the equipment, screen, and architecture "works."

Jack & Tim are completely correct on picture and sound. Louis

Posted by David Kilderry (Member # 142) on 03-16-2007, 10:58 AM:

I can't understand how some US drive-ins use only 2k xenon lamps; what must the image look like with such low power?

In Australia most big carbon lamphouses like the Ashcraft Super Core-Lite etc, gave way to Xebex or Strong 5k xenon lamphouses.

Regular xenon alignment, reflector cleaning and fresh lamps go a long way to a good on-screen image. I start our 5k lamps at 135 amps and move them up slowly to the max 150 amps before removal.

I do not rotate the lamps any longer as the manufacturers state that the necessity is greatly reduced these days due to great advances in the quality of the quartz envelope and its resistance to blackening.

I find the larger the lamp, the more acute the light output is as it reaches 100% life.

David

Posted by Bill Enos (Member # 440) on 03-16-2007, 03:01 PM:

To those of you who are in major metro areas anywhere, how far is it to the nearest operating drive in? The nearest one to Richmond, Va. in in Fork Union, VA., 60 miles away. It is open Memorial Day to Labor Day, Friday and Saturday nights only. Plays current second run.

Posted by Adam Martin (Member # 641) on 03-16-2007, 03:14 PM:

quote: Scott D. Neff
We seem to have installed a number of screens that are 36x76. Any suggestions for lamp power for one of those suckers?

Steve G. has previously recommended 13*h^2 for a flat image. That would be almost 17,000 watts for that size screen, which is way more than the film could handle without damage. You'd be stuck using 7K in a decent lamphouse and with decent optics and hoping for the best.

Posted by Dave Bird (Member # 490) on 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....

Posted by Monte L Fullmer (Member # 2797) on 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.

Posted by Sean McKinnon (Member # 612) on 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.

Posted by Monte L Fullmer (Member # 2797) on 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

Posted by Gordon McLeod (Member # 33) on 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

Posted by Jack Ondracek (Member # 1466) on 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.

Posted by Louis Bornwasser (Member # 3063) on 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

Posted by Monte L Fullmer (Member # 2797) on 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.

Posted by Jon Paul Johns (Member # 3443) on 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

Posted by Tim Reed (Member # 137) on 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.

Posted by Jon Paul Johns (Member # 3443) on 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.

Posted by Tim Reed (Member # 137) on 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?

Posted by Jon Paul Johns (Member # 3443) on 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

Posted by Gordon McLeod (Member # 33) on 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

Posted by Jack Ondracek (Member # 1466) on 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.

Posted by Tim Reed (Member # 137) on 04-08-2007, 08:09 PM:

quote: Jack Ondracek
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.

No, I was talking about a mixer at that point.

Gordon has a good point, about the matrix pumping sounds.

Jack has the answer with the Behringer number... [thumbsup]

Incidentally, I've used these on Carmike mono houses that are running DLP:

Rack mount mixer

Posted by John Wilson (Member # 269) on 04-09-2007, 05:12 AM:

There are houses running DLP yet are still in mono? That's just bizarre.

Posted by Tim Reed (Member # 137) on 04-09-2007, 10:46 AM:

In instances where they haven't yet bought the speakers, and/or had the work done in the auditoriums to upgrade existing mono houses to 5.1, yes, they are running DLP monaurally. All the booth work is ready... racks, wires pulled, etc.

Posted by John Wilson (Member # 269) on 04-09-2007, 04:26 PM:

Still, even if it's only a mono house...it's GOT to be better than 35mm...it's [dlp]

after all.

Posted by Daryl C. W. O'Shea (Member # 1303) on 04-10-2007, 12:18 PM:

While you're ordering a mixer be sure to get yourself a compressor too. Even if you use little compression and just use it mainly for limiting it'll be worth every penny.

I've used a half dozen or so Alto ACL2 Pro units in drive-ins with good results. They're cheap as hell, compared to say a Lexicon, too. Their manuals even reference "Good old analog technology".

http://www.altoproaudio.com/html/dynamic_processors.php
http://www.altoproaudio.com/html/details.php?ID=23

If anybody buys these, make sure you get the ACL2 PRO and not just plain ACL2. The "pro" version can link the channels for stereo operation, the base version can't link channels (and is missing a gate rate control IIRC).