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Hello everyone! My first thread here but fear not, I try to avoid to be FAIL-stamped on my forehead. :bigsmile:

I am just trying to generate brainstorm and conversation here among the DIY folks by asking: 'Do you remember Sensurround and film called Earthquake? Well to be honest I don't because I was not born back seventies, but in Sensurround equiped theatres they achieved 120dB SPL at 5Hz therefore simulating actual feeling of an earthquake!

From wikipedia, Earthquake (film)
Wikipedia said:
A famous example is Grauman's Chinese Theater in Hollywood, California, where the "Sensurround" cracked the plaster in the ceiling. Ironically, the same theatre premiered Earthquake three months later – with a newly-installed net over the audience to catch any falling debris – to tremendous success.

The "Sensurround" process proved to be a large audience draw, but not without generating a fair share of controversy. There were documented cases of nosebleeds generated by the sound waves.
Now for the real question!

What is needed to generate 120dB SPL at 5Hz in normal Hometheater? I am especially interested what DIY guys/gals have to offer. :) If it is hard to achieve in small HT conditions then imagine what kind of systems they had in 1970 when Sensurround debuted. :yikes:

I myself have a long way to go until I reach the level of 120dB at 5Hz, but my ongoing 'Dual Exodus Audio Shiva-X sealed' -project is a good start to reach that high level punch. :boxer:

Discuss and feel free to comment and flame me. :yes:
 

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Welcome to the Shack Jukka,

Maybe a sealed 100" driver ?? :R, I just watched Cloverfield today and everything was shaking in the house. I don't know if I would want more :hsd:
 

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It is not necessary to go that low to achieve the rumbling like an earthquake and is not an easy task to go that low with that sort of SPL.
Realistically 10Hz is plenty low for even the largest of Home Theaters.
Where did you find the actual 5Hz information I highly doubt that it went that low.

Welcome aboard!
 

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I'm pretty sure that claim is incorrect. A theater even nowadays would be more than hard pressed to achieve 120db in a theater setting at 5hz. They aren't interested in putting that kind of money into just the subwoofer system.
 

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Sensurround involved the installation of large, low frequency, horn-loaded speakers which contained specially designed 18-inch Cerwin-Vega Model 189E drivers in custom black wood cabinets. Three horn configurations were available, Model-C (Corner), Model-W (Folded Bass Bin) and Model-M (Modular). The Model-C and -M horns required stacking in groups of four, increasing effective horn mouth size to achieve the low frequency target. 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. The Model-M horn had a dedicated "Mouth-Extender" available when it was used in the front of the theater. While installation was customized and varied in each theater, the Sensurround horns were typically placed beneath the screen in front and in the back corners of the theatre. Often, rows or sections of seats would have to be removed to make room for the large Sensurround horns. In large theaters, up to 20 individual horns might be used along with custom-built bat wings and mouth extenders.

The deep bass signal fed to the Sensurround horns was controlled by a separate control box in the projection booth. Audio from the film soundtrack was fed to the control box which fed 1,600 watt BGW 750 audio amplifiers driving the speakers.[3]When triggered by control tones on the film's soundtrack, the system generated a pseudorandom noise between 17 and 120 Hertz at sound pressures ranging from 110 dB at the center of the theater to a maximum of 120 dB 4 feet in front of any horn.[4] The resulting rumble could be felt by audience members as well as heard.
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Discussion Starter #7
I'm pretty sure that claim is incorrect.
It seems like you are correct. This whole idea came to me when I first read Wikipedia - 'Subwoofer history' page which said:
Subwoofers received a great deal of publicity in 1974 with the movie Earthquake which was released in Sensurround. Initially installed in 17 U.S. theaters, the Sensurround system used large subwoofers which were driven by racks of 500 watt amplifiers which were triggered by control tones printed on one of the audio tracks on the film. Four of the subwoofers were positioned in front of the audience under (or behind) the film screen and two more were placed together at the rear of the audience on a platform. Powerful noise energy in the range of 5 Hz to 40 Hz was generated at the level of 110-120 dB(SPL). The new low frequency entertainment method helped the film become a box office success.
It indeed says at Sensurround page that the frequency range was 17-120Hz. I believe that is more sensible. :T
 

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Wow, I did not know wikipedia was so wrong of this film. It is full of midbass! :rofl2:
Yeah maybe they should have used waterfalls. The Truth is out there. Still even mid bass and sub bass is in your chest regardless.

I don’t think Dante’s Peak even goes below 18Hz? I’d have to run that one though sometime.
 

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Just doubled checked with leads connected to the DVD players left and right out minus LFE.1 because LFE.1 isn’t carried on the left and right and it’s the same as the waterfalls that I have just finished a few hours ago.

I know what the real cinema Event was like I’ve sat though it 3 times at the age of 8. Back then a ticket was 79p to see Earthquake today it’s around £8 pounds at best and they don’t even let the Dolby SR-D thunder away even 70mm seems weak compared to the Empire Leicester Square that can put any film in your face.

I wonder what Earthquake was like at the Empire? I’d have to send private message to a former retried projectionist and get some feedback providing of course he was at the site back in 1974 might have been working at different cinema.
 

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You would be surprised at how much your chest moves if you have enough SPL at even 30-40 HZ 120db in that range even is enough to put a smile on your face.
 

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What is needed to generate 120dB SPL at 5Hz in normal Hometheater? I am especially interested what DIY guys/gals have to offer. :)

I myself have a long way to go until I reach the level of 120dB at 5Hz, but my ongoing 'Dual Exodus Audio Shiva-X sealed' -project is a good start to reach that high level punch. :boxer::
This is EASY. Buy 14 more Shiva's and make 7 more of your current SW, buy 2 QSC PL6.0's to power each set of 8. Throw on a movie and enjoy :hsd:. Should be good for 135-140db in the 40-80hz area too.:hide:
 

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There is one driver of which I am aware that would be capable of producing massive SPL down to 5Hz. The Phoenix Gold Cyclone which is no longer in production. It is very likely a pair of these rotary woofers would be capable of producing 115-120dB at 5Hz.

If you are interested in getting them look on ebay the going price is around $450 a pop. Phoenix still refurbishes broken models for about $150 as well.

Now, the pragmatic side of this recommendation: It is unlikely you will actually find source material to make use of these woofers at such frequencies, but you could do it to say you have the power :).
 

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There is one driver of which I am aware that would be capable of producing massive SPL down to 5Hz. The Phoenix Gold Cyclone which is no longer in production. It is very likely a pair of these rotary woofers would be capable of producing 115-120dB at 5Hz.

If you are interested in getting them look on ebay the going price is around $450 a pop. Phoenix still refurbishes broken models for about $150 as well.

Now, the pragmatic side of this recommendation: It is unlikely you will actually find source material to make use of these woofers at such frequencies, but you could do it to say you have the power :).
Actually today's high displacement 18's like Mal-X's will move more air than the Cyclone's will as far as I know. The foam vane only had so much area with a 2.5" range of motion. They were interesting and really good at moving air for the time though. Would've been cool to see what would've happened had the design been expanded on by PG further.
 

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The Phoenix Gold Cyclone is considered by most to be an abject failure. The sound quality is terrible.

Depending on which blades are used the Thigpen Rotary Sub can be tailored for a rising response as the frequencies drop. It's extremely efficient. Using a modest 200 watt amp 100dB+ output @2Hz was recorded at the initial public debut.

When this device is operating one must be careful to avoid being in the room if there's a history of inner ear problems. For those not so afflicted the experience of 'hearing', yes I said 'hearing' 5Hz, is something words can't describe.
 
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