Film-Tech Forum ARCHIVE: A simple solution to better drive-in sound?

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Posted by Peter Berrett (Member # 672) on 08-01-2002, 10:10 PM:

Hello all

On the Dandenong Drive-in thread someone pondered whether it might be possible to get surround sound or at least a better standard of sound in people's cars. After some thought I came up with a proposal that might achieve just that with some degree of simplicity.

Essentially many drive-ins these days use a stereo fm transmission to give stereo sound to those with fm car radios. Radios are often available for hire in the snack bar for those who do not have an fm car radio.

I propose that the drive-in keep its existing fm stereo transmission for usual theatre goers but have supplementary transmissions for those desiring a higher standard of sound.

Here's how I envisage the additional channels would work. (Note that the existing stereo fm transmission would be kept separate to the following so that existing patrons can get their sound as per usual)

Essentially the surround sound would be reduced to 4 channels

front left
front right
rear left
rear right

The front channels would be broadcast as a stereo fm transmission on one fm frequency and then the rear channels would be broadcast as a separate stereo fm transmission on another frequency. All a patron would have to do to get this surround sound would be to come to the drive-in in his fm radio equipped car and bring along a boom box (a portable stereo fm receiver). He would tune his car radio to the 'frontal' stereo fm frequency ensuring of course to fade any rear speakers he has in the car. He would then tune the boom box to the rear stereo fm frequency and place the boom box in the rear of the car or station wagon facing the front of the car. If the boom box speakers are detachable they could be detached and placed at either side of the rear of the car to give greater separation. Lots of people have boom boxes or portable fm radios these days.

This seems like a low cost, technically feasible way of providing a better sound experience to drive-in patrons without interfering with the sound reception system of regular drive-in patrons.

Thoughts please? Feasible? The only problem I can see are that (1) the drive-in would need to ensure that the left and right channels are swapped for the rear stereo fm transmission as the boom box will be facing the opposite way to the car radio and (2) high quality cinema sound systems may have greater then a 4 speaker system. One may have to mix a few channels to reduce the sound down to 4 channels. Even so a 4 speaker system along the lines of that outlined above should give a better sound expererience than just a 2 speaker system.

I'll hand over to our resident sound engineers. Could this work?

cheers Peter

Posted by Paul G. Thompson (Member # 655) on 08-01-2002, 10:50 PM:

Oh, I am sure it is possible, but the rear channels might have to be piped in just like the old drive-in's used to do with the mono sound. Unfortunately, there are very few (if any) car radios that will receive 4 channels of matrixed sound. Sansui did that in the early 70's with their Quad receivers, but that format really never took hold. The surrounds were loose as a goose, and just didn't produce what you wanted to hear like you do in a 35mm stereo format.

I think that the cost of piping in surround sound to cars (and handing out speakers, not to mention maintenance of the speakers and field) would be cost prohibitive.

There may be some technology available to do what you want, but I have not heard of it if there is.

Just my .02 cents worth.

Paul

Posted by Scott Norwood (Member # 30) on 08-01-2002, 11:47 PM:

Do more channels necessarily equal "better"?

I've heard some very impressive two-channel FM-stereo sound in drive-ins; I believe that they were using that SMART box that is designed for drive-in use that decodes the NR (A-type, I think) and provides a 2-channel signal to the transmitter. Do we really need the extra channels for drive-in use? In most cases, the limiting factor for sound quality would be the cheap radios that are generally built into cars.

Posted by Adam Martin (Member # 641) on 08-02-2002, 02:37 AM:

Someone should set up a 5.1 processor with five transmitters, one on each main channel. Direct customers to park in a specific place and tune to the matching frequency ... ie, park in the front left of the lot and tune to xxx frequency (which matches the stage left channel). Put the cars with the boom-boom radios in the front row. Then everyone sits at the snack bar patio and enjoys the show in 5.1 surround.

Posted by Tim Sherman (Member # 569) on 08-02-2002, 02:53 AM:

scott that smart processor you are talking about is the MOD II-B DIT, a special version of the MOD II B for use in drive-ins. It has both SR and type A NR and also mono. I currently run two of them and love them.

And i don't really think that adding transmitters and a boombox would be worth the hassle. Most of the customers have enough trouble remembering one freq. let alone two of them. I can also just imagine how many people would complain and experience horrible sound because they were on the wrong frequency and were just listening to the rears. Another point is that i don't really think that many people care about the surround sound in a drive-in, think about it, every single mini van and SUV that park backwords and watch the movie from the back of the car is listening to the stereo sound backwords. the right channel is now their left and the left now their right.

If you are looking at getting better sound at a drive-in then get better equipment. like the smart mod II b dit, Reverse scan readers, a good transmitter like one from broadcast warehouse, and a good Stereo compressor/limiter like the behringer ultra-dyne 9024.

Trust me you can tell

------------------

http://www.autoramadrivein.com

come on out to the drive-in and spend a night out with the stars"

Posted by Steve Guttag (Member # 268) on 08-02-2002, 06:38 AM:

The surround sound idea you mention would work. I would put the surround frequencies at the opposite end of the dial though..So if you are near 88MHz on your main channels...be up near 108 for the surrounds to avoid confusion. It might give you a novelty.

Steve

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"Old projectionists never die, they just changeover!"

Posted by Bobby Henderson (Member # 840) on 08-02-2002, 05:06 PM:

Of course, I'm still hoping for 5.1 audio capability to become a standard item in car stereo systems. But a few things have to happen along the way before it can become commonplace:

"Next generation" music-only formats like DVD-A and SACD need to have new music title releases made for the format and released on the same day/date as the standard LPCM music CD. This move would put more pressure to install DVD-A, DD, DTS, etc. 5.1 surround capability in car stereo systems. Right now there is very little demand for it because title availability just plain sucks much ass. If a 20 year old Foreigner album is among the best efforts DVD-A's proponents can put out, the format will languish in limbo and eventually die.

A radio broadcasting industry has to settle on a digital transmission format so digital-based receivers can become common in cars.

DVD-Video systems in cars are nice, but really won't drive the car stereo market hard enough alone to make 5.1 surround common in cars. The DVD-A and SACD formats have to do it if at all possible.

If the 5.1 music thing and digital radio broadcasting thing can become standardized, then there should be no problem for a drive-in booth to simply digitally broadcast something like a Dolby Digital 5.1 audio signal for the cars to decode and play. It would be really simple to do. The gigantic challenge is just getting the care stereo "infrastructure" in place.

Posted by Gordon McLeod (Member # 33) on 08-02-2002, 06:03 PM:

Since the Mod2b DI does nothing to the LT and RT other than providing nr the FM transmitter recieves Lt and Rt
Several high end car stereos already offer surround decoding so all they would have to do is switch it on

Posted by William Hooper (Member # 71) on 08-02-2002, 06:11 PM:

For quick, low hassle but splashy fun, I'd say just set up a bunch of old bass bins around the lot aimed at the cars, & then tightly gate & low-pass the subwoofer channel to them to just wallop Godzilla footsteps, explosions, etc.

The neighbors would love it, too.