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Sensurround: rumbling audiences since 1974!

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#1 of 4 LanceJ



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Posted August 15 2009 - 10:18 AM

Since this theatrical subwoofer system debuted years before many of HTF's members were born, I thought it would be interesting to post about this theater-based subwoofer system. And if anyone was there when it debuted - I was! - go ahead & post your own impressions of it for this trip down memory lane.

I was reminded of this groundbreaking /img/vbsmilies/htf/smiley_wink.gif"> system when I was at a music store recently & spotted a dvd version of Earthquake, one of the many disaster movies which came out in the 70s. It's not too bad to watch if you have a couple of spare hours on your hands and the effects, while not CGI, are decent (though one scene in an elevator contains the cheapest & incredibly fake-est "special effect" I have ever seen in a major-studio release). About seven years ago I bought the dvd version put out by Good Times Video but was disappointed to find it lacked the extremely low frequency bass I heard as a kid in the theater. So I was excited, temporarily at least, to see that the Universal version I saw included a Dolby Digital format I had never seen before - 3.1 - and figured aha! this must include that fun rumbling stuff I so vividly remembered. But I wasn't sure so left it at the store & when I got home did some research on it. Looks like the Universal version still doesn't include that fun rumbly stuff, but I did learn more about the Sensurround system and how much it affected future movie soundtracks.

The following wikipedia page is crammed full of information on the Sensurround system, so I'll just include some of the highlights contained in it.


What it is:


 Sensurround is a process developed in the 1970s by Universal Studios to enhance the audio experience during the presentation of theatrical movies. Specifically developed to showcase the 1974 film Earthquake, the process was also used in three subsequent films, Midway (1976), Rollercoaster (1977) and in the theatrical version of Saga of a Star World (1978), the Battlestar Galactica pilot.
Eventually there were improvements made, and Sensurround II and III came into being.


 Sensurround involved the installation of large, low frequency, horn-loaded speakers which contained specially designed 18-inch Cerwin-Vega Model 189 E drivers in custom black wood cabinets........They came with special extenders used to widen the mouths of the horns and take advantage of the theater walls to further increase low frequency extension.
I most definitely remember these very large & rather ominous horns looming in the darkened corners of the theater. I also remember seeing the "clean" patches where the several rows of seats had been removed to make room for them.

The following is probably why neither dvd I mentioned above contains those extreme low-frequencies*:
The original Sensurround design used for "Earthquake" employed a pseudorandom noise generator, designed by D. Broadus "Don" Keele, Jr., to create the low-frequency rumble, with the waveform matching that of the 1971 Sylmar earthquake.[citation needed] Two low frequency control tones were printed on the film's mono optical or magnetic track; from the projector, the tones entered a control box in the projection booth, which fed low frequency pseudorandom noise to 1,600 watt BGW 750 audio amplifiers driving the speakers.[4] The control box generated a pseudorandom noise signal with energy between 17 and 120 Hz. The control track method was employed because there was no way to accurately record bass lower than 40 Hz on an optical or magnetic film soundtrack at the time.

Despite no computer technology being used, analog systems can be useful if their design is clever enough:
For the film Earthquake, Sensurround was activated during the quake scenes to augment the conventional soundtrack.[6][7] In addition, portions of the main soundtrack were redirected to the Sensurround horns to create a partial surround sound effect. The control tones recorded on the film's optical or magnetic track triggered the rumble or surround sound effects as well as controlling their volume and the overall blend of the main soundtrack and low frequency noise effects.
FYI: later in the article, it does mention that other soundtrack versions (there were several)included a true surround sound soundtrack.

With such large subwoofers and so many of them, the following was bound to happen!
The excessively loud Sensurround caused additional disruptions for theaters playing Earthquake, including structural damage in some cinemas. At Mann's Chinese Theatre in Hollywood, theater management stretched a safety net over the seating to catch errant pieces of plaster after a test screening revealed the process had actually cracked the ceiling. In Germany, Sensurround movies were only allowed to be played in single screen cinemas.

BTW maybe an experienced Californian can comment on this: one thing that bothered me about the rumbling is that the rumbling sequences would immediately start and stop i.e. there was no "fade in" or "fade out" of the bass effects. I've never experienced an earthquake firsthand, so am not sure if that is what actually happens with the real thing.

* there is more about this issue in the article section labeled "Remastering for DVD"

#2 of 4 gene c

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Posted August 15 2009 - 10:53 AM

First off, thanks for the history lesson. /img/vbsmilies/htf/cool.gif">

As A kid (15 in '74) I wasn't able to make it to the theater very often but I do remember hearing about the special sound system at one of the theaters showing some movie. Must have been Earthquake.
Also, even though it was only yesterday I can't remember why I was looking at CV home page but I did read something about those 18" drivers used in some theaters in the History of CV section

Real earthquakes are definently felt before they are heard. Then comes the audible rumble. Much like a train coming and going. BTW, most earthquakes come and go un-noticed and many others just cause a little shaking and rattling. But every once in a while....
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"Everyday room": Panasonic 58" Plasma, Dish HD DVR, Pioneer Elite vsx-23, BDP-23 BR, dv58avi universal dvd player, Paradigm Studio 20 V1, CC-450, Dayton HSU-10 subwoofer.

"Movie/Music room": Toshiba 65" DLP, Dish HD receiver, Marantz 7005, CC-4003, BD-7006, Polk LSI25's-LSi7's-LSiC, 2 original Dayton 10" "Mighty-Mites" subwoofers. (subject to change without notice).
Also have  MB Quart Vera VS05 +.....too much to list. Help me.


#3 of 4 Clyde's Place

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Posted August 15 2009 - 12:10 PM

 I was lucky enough to experience Sensurround first hand, but just barely.  Earthquake had been released in late 1974, but was still being shown during the summer of '75 at a theater in Cincinnati called the RKO International 70.  It originally had been just the RKO Palace but the name was changed in the 60's to highlight that it was a showcase for wide screen films shown in 70 MM such as The Sound of Music, 2001: A Space Oddyssey, and even a revamped (as it turned out, not for the better) wide screen version of Gone With The Wind.

The reason I was able to see the film is because my wife and I had won a weekend in Cincinnati at a Hotel, and tickets to see the Reds for the three days.  Two things I wanted to do on the trip (we lived over a hundred miles away, so we didn't get into Cincinnati except for Reds/Bengals games or King's Island.  And you generally went to those events and then drove home.) was to see Earthquake in Sensurround, and the much talked about Jaws, which had just opened (It would take six months to a year for a hit film to arrive in our town.)  Both events turned out to be memorable.  Earthquake for its Sensurround, and Jaws because we couldn't get into see it until 2:30 in the morning (but as it turned out, it was well worth it.)

We arrived at the theater just as the previous showing was wrapping up.   We waited in the lobby, but when the Sensurround kicked in, right away you knew you were in for a treat as the noise filled the theater and the wall and doors between the auditorium and the lobby would vibrate.  It was also a bit unnerving, but made you that much more anxious to want to see what was on the screen.

Frankly, it is the Sensurround that made Earthquake memorable, especially during the long main earthquake scene.  As I recall, the vibration actually synced well with what was going on in the film.  During a mild tremor, the rumbling wasn't quite as pronounced.  During the really big Earthquake, it started out as a bit mild then gathered force as the tremors in the film reached their full ferocity.  And when the Earthquake stopped on the film, the Sensurround ended just as abrubptly as well.  

It was quite an interesting film experence and I considered myself lucky to have experienced it because the film ended it's run shortly thereafter (There wasn't but a handful of people in the theater by the time we made our trip).  Certainly one of my more memorable film experiences (but it does not surpass seeing How The West Was Won in full fledged, floor to ceiling, wall to wall Cinemrama at the Capitol Theater), and there are numerous articles on the subject.  As it turned out Sensurround was also impractical for multi-screen cinemas causing a disruption in other nearby auditoriums and also causing patrons to complain.   Of course, you know about Jaws, but seeing Jaws in a theater full of patrons was far and away a much better experience then watching it at home.

Oh, and the Reds went on to the World Series that year and played a team called the Boston Red Sox that I don't remember too much about.  Just kidding of course.


#4 of 4 Todd Stout

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Posted August 15 2009 - 05:04 PM

I had a brief taste of Sensurround when I was a kid. I can't remember what movie I was at the theater to see but I do remember seeing the large speakers that were set up towards the rear when I first walked in. I was wondering what the heck they were there for and I would soon find out. One of the trailers they showed that day was for Battlestar Galactica in Sensurround and oh boy was I impressed! Whenever there was an exterior shot of the ship, the entire theater would shake. Unfortunately I never did see the entire movie that way but I'll always remember seeing... and feeling that trailer.