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 Post subject: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 24 Jul 2020, 23:52 
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Hello.

So, after reports came in late yesterday of a man whose entire being capitulated under an assault of extreme bass terror while watching the (now infamous?) Earthquake Laserdisc, I decided to break out my little Zoom U-44 audio capture rig and conduct an analysis of the two audio tracks contained on said wonder discs.

These are my subpar findings. Please look forward to them. :angel:

Disclaimer:

Capturing the audio proved to be a real pain in the rectum. Only because for some reason Reaper decided that it wanted to constantly crash on me at various intervals. Eventually I got two captures. One of the analog stereo track, the other of the digital stereo track. Unfortunately I captured one at 44,100 16 bit, the other at 48,000 24 bit so there is disparity in that sense. However I ran FFT analysis at such a high rate this is still going to be really bloody accurate. Or, accurate enough for the purposes of this test.

It took so long to stop Reaper crashing during capturing the audio that when I finally got two captures and saw the sample rate differences I just didn't have the will to do it all over again. I'm sat here watching my beloved Mets playing the Braves on Opening Day and it's taken 5 innings to get it wrapped up! #LGM :thumbup:


Background:

This whole thing stems from recent forum discussion of the exospherically noisy 70's disaster flick Earthquake and it's Oscar-winning use of building-destroying Sensurround bass. It appears that this particular disc Earthquake (1974) [42072] contains the original Sensurround audio track that was used in cinemas (and promptly turned them all to rubble) in 1974.

The discs sound great on my Yamaha YSP-2700 16 speaker soundbar and sub setup. Though my subwoofer will only go as low as 50hz. You need to be getting down to around 20-30hz to get the full buttock-splintering effect. Of course, to get the full fat, full beans experience you will be wanting to pick up a bunch of original 1970's Cerwin Vega horns (available on eBay sometimes) and placing about 50 of them in a wall to get somewhere near the original effect audiences heard in 1974.

Fellow forum user laserfanhld-gb has a half decent :lol: home cinema at his gaf and promptly purchased a copy of the same Laserdisc. He was underwhelmed with the Sensurround track along with any surround or stereo processing that may be in his chain and ejected the disc feeling somewhat underwhelmed.

A second attempt, this time letting the audio flow through untouched proved to be the sweet spot. And thus his body exploded in to a beautiful confetti shower as it surrendered to the extremes of proper, beautiful Sensurround destruction. He's going to explain the experience in his own words another time, so I'll leave it there for now.

The goal of this entire process is to analyse the main quake, where Sensurround is pushed to the limit, to see if there are differences between the tracks and if indeed the tracks actually hit Sensurround frequencies. I personally think that the Digital Stereo track sounds a bit squashed, like there is too much going on to really make it sing. I obviously cannot comment on the full force of the bass as I don't have the rig to cope with it at all. On my setup though, I prefer the Analog Stereo track.


Process:

Sample rate woes aside, to make this as fair as possible I captured the entire duration of the earthquake. The quake begins around 30 seconds in to Chapter 21, which is at the very start of Disc 1 Side 2. The opening 30 seconds or so of Chapter 21 are fairly quiet, so I started recording at 15 seconds in. This was a good marker to ensure an equal start for both captures.

The earthquake lasts around 8 and a half minutes, so I captured it in full on both occasions.

The audio was captured in Reaper using a Zoom U-44 audio device over USB-C. I used a toslink cable to capture both the analog and digital tracks (confirming this with the decoder output on my soundbar, Analog and PCM respectively). No point using RCA imho.

Both *.wav files were then run through Speck for spectrogram analysis. I then ran a full FFT analysis of both tracks in Adobe Audition CC 2020 and looked at the results.


Findings:

TL;DR the above? Grand. Here's the results. It's quite interesting.

Below is an analysis of the entire quake on the Analog Stereo track. You can see the frequency range spans across a wide spectrum but what we are interested in is how low it gets. In this instance we're hitting 23hz at it's lowest point according to Adobe Audition CC 2020.

Image

Taking a look at the Digital Stereo track yields slightly different results and a clearly different curve. Note that here the audio apparently goes down to 1hz!? I'm taking that with a pinch of salt, though the curve is interesting as you can clearly see the swoop between 1hz and 20hz. So even if we discard the really low frequencies detected, we're still hitting reasonably attainable frequencies of, say, 10-20hz. Well within Sensurround levels. Incidentally, although the screenshot doesn't show it, the average volume at 23hz is -67db on this one, not far off the Analog Stereo track average at 23hz.

Image

Below is a comparison of both tracks, taken at the very start of the earthquake. This is the scene in the cinema when the ground begins to shake as the actors on screen open fire. First the Analog track, then the Digital track.

Image

Image

Finally, here are two full spectrograms of the Analog and Digital tracks respectively. I think here you can see some differences between the two tracks. To my completely inexperienced eyes, it looks like it captures some differences, though it looks fairly minimal and not as good a representation as the frequency analysis waves.

Image

Image


Conclusion:

I'm no sound engineer or expert, but I think there are definitely some findings here even to my very inexperienced eyes (ears? :think: ). It appears that the Sensurround track is present (note the prolonged, super-low frequencies throughout the quake) that's not really ever been in doubt. The digital track appears to me at least, to be slightly narrower and squashed. Even taken at a different sample rate.

With all of this in mind, I think you really will need a rig that can have it's legs stretched by such a demanding low frequency soundtrack. This is probably why it doesn't sound at it's best on the average home sound system, even a <30hz capable rig.

Regardless, I'm glad I went to the trouble of documenting all of this. Maybe it will prove enlightening to someone far more experienced? Maybe I'm full of s**t. Either way, I hope this post helps in some way. :thumbup:

Side note, as I type this the Mets just won their opening game. That's the high point of the new baseball season over and done with for me then! :lol:


Further reading:

Here is some interesting information from Kef who state that Sensurround could get as low as 10hz!

https://us.kef.com/blog/sensurround-a-s ... experience

Some discussion from former Sensurround exhibitors and enthusiasts:

http://www.film-tech.com/cgi-bin/ubb/f1/t002087/p1.html

A very thorough Amazon review of the Blu Ray debacle:

https://www.amazon.com/review/RGVHFWXC7FKIQ

More bowel-perforating Sensurround information than your mind can handle, in 70mm!

https://www.in70mm.com/library/process/ ... /index.htm
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 25 Jul 2020, 00:30 
Jedi Knight
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“The audio was captured in Reaper using a Zoom U-44 audio device over USB-C. I used a toslink cable to capture both the analog and digital tracks (confirming this with the decoder output on my soundbar, Analog and PCM respectively). No point using RCA imho.”

I don’t understand this. There is no LD player made (that I know of) that will send the Analog tracks over TOSLINK. Maybe I’m not reading what you wrote correctly but Analog LD tracks only come from the RCA outputs.
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 25 Jul 2020, 00:59 
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No you read it right, I wrote it wrong. I keep forgetting about my wild setup with cables everywhere!

I have a DAC, toslink switch and splitters in the chain. This lets me then run a single toslink across to the U-44 input and switch between tracks.

I have a great Yamaha Pocketrak recorder I can do the RCA directly on at a later date (don't have it to hand at present). The U-44 only has XLR inputs, not RCA so I can't do it using that.

Sure all this may skew things a bit but there's definitely differences there. I'm no Dr. Dre though, just a bloke trying to document stuff nobody cares about but one person may stumble upon in 50 years time and be delighted the information was recorded.

It is late and I have half an eye on opening day so forgive the lazy write up! :thumbup:
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 25 Jul 2020, 01:41 
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I guess I still don’t understand. I thought this was a comparison between the Analog and Digital soundtracks on the same LD. How are you recording the LD’s analog soundtrack? If you can’t use the analog ins on the Zoom then you can’t use it to record the LD’s analog soundtrack.

Please forgive me if I misunderstood something.
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 25 Jul 2020, 12:59 
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This is really cool Ted. Thanks for taking the time to do the capture. Its very interesting. I'm keeping an eye out for the Japanese release of Earthquake. I'm really looking forward to hearing the sensurround track. I will have to check my subwoofer specs to see how low it goes.

I suppose the next step for you would be to acquire and test the other films with a sensurround track. Rollercoaster and Midway, I believe.

I own Rollercoaster on LD although I am yet to watch it. I'm not sure if it has the sensurround track but I think I read somewhere that it does. Midway does according to the database.
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 25 Jul 2020, 13:38 
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Regarding the ADC process and output here, I'm not overly fussed about it. Same way the sample rate screw up doesn't bug me too much (though I will go back and fix this and also do a proper, direct RCA capture to my Pocketrak for completeness when I get it back in my possession). This was just to get the tracks off of the LD as quickly and conveniently as possible with the kit I have available to me.

Looking in to ADC I don't think it's going to skewer the results too much, if at all, given the sample rates used etc. You could go down a humongous rabbit hole with all of this and to be honest I don't want to sit in front of my TV with stuff wired up to oscilloscopes and power cables suspended in mid-air by rare minerals that measure the noise in the dead air of my sitting room and I'm sat there wired up to a brain scanner like the kid in D.A.R.Y.L. :lol:

It's close enough, and the results do show that the frequencies are definitely in the right Sensurround range. The Digital Track surprised me with just how low it went. 10hz isn't even audible to the human ear is it? I think at that stage you are getting in to where bass starts vibrating your ribcage, bowels perforate and eardrums explode and so on.

We will never be able to recreate 100% Sensurround at home, the equipment is just not there (though I can imagine there must be someone crazy enough to try replicating it!). When you're talking literally entire walls of Cerwin Vega horns that could blow an aircraft carrier over and a bunch of other kit to interpret the signals on the soundtrack, it's just not going to be possible.

There is an interesting chap on YouTube though who has some wild SSDS, DTS etc gear in his home who may just be able to get close to it? :think: I forget his name but he has some really wild stuff in his gaf. Proper cinema gear.

The closest we have right now is the smouldering rubble left over at laserfanhld-gb's gaf the other day. Any other folks here stretched Sensurround's legs at home? How did it work out? Keen to hear your takes on this!

@odotb3:

Thanks a mil. It took me all 9 innings of the Mets game last night to write this up. I was knackered so missed bits here and there, apologies all it was late!

I would like to try Midway for sure. Rollercoaster I have to pick up the German Blu Ray as that is the only one that has the Sensurround track untouched on it. The USA Blu Ray has it too I think but I am sure I read somewhere that it was processed and thus messed about with and not the 'true' audio track so to speak. The Rollercoast LD does have the Sensurround track afaik.

Check your subwoofer at home on the back it should say what it's rated at. Mine is 50hz so I can't get anywhere close yet it still rumbled along nicely. You really want to be around the 20-30hz mark, and if possible make your set up a .2 (or better) by adding an extra sub or more to your setup. Keep in mind though to get even a glimpse of what it must have felt like back in 1974 you'll want to multiply your subwoofers by about a jillion!

Check out the in70mm link I posted, there is some superb Sensurround information there. What a shame it pulled ceiling tiles off of cinemas and cracked their foundations. We could have been enjoying rubble landing on our laps in cinemas today! :(
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 25 Jul 2020, 14:31 
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Disclord and Laserbite would talk about these films.

Did anybody else do a search for their posts on these films with sensurround?

While this is a very cool thing and you do need a few subs or whatever in your house to replicate it.
1 I doubt my old house would stand up to 2 or 3 viewings of said films.
2 I'm sort of glad these films aren't really my taste, I can watch them and watch them once in a while but then that's it,

I believe I saw Earthquake within the last 3 years, not a great film but do remember Marjoe with his non hippy wig, if that's the right film.
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 26 Jul 2020, 03:23 
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Yeah, Disclord was super into this movie and he had a way of totally understanding any subject he was interested in so I'd look up whatever he said. I'm sure there's something to be learned.
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 26 Jul 2020, 12:09 
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Found this excellent thread with lots of useful information from disclord. He appears to confirm a lot of the chatter surrounding the various pressings of Earthquake across formats, including the ropey Blu Ray (doesn't specify the German Blu though which I still understand is the one to get).

Listening to Sensurround Laserdiscs

Also he seems to give more detail around the 'squashed' audio that I think is present on the digital track.

Maybe the Japanese P&S disc is the one to go for if you want full, unadulterated, pure skeleton shattering destruction?

Capture the audio off of that and mux it to the German Blu which has the best bitrate anyway?

Does anyone know if the extended TV version contains the Sensurround track? I have a moody version of it but the audio is not pure and true.

Feck it, I will see if I can analyse the frequencies on it.
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 26 Jul 2020, 14:28 
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OK Soak your nut in this one: Listening to Sensurround Laserdiscs

Get ready for some good ole reading, disclord and laserbite were both crazy about this film, others too
as the topic has 31 posts.
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 26 Jul 2020, 14:51 
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Here is another interesting thread on the subject:
Rollercoaster 1977 mono

Sadly it confirms that the sensurround track is not present on the Rollercoaster LD. :(

How strange is it that the P/S release of Earthquake has the proper sensurround track but the re-release that was apparently remixed by Universal still sounds so earth shatteringly good? It begs the question, how good does the original release sound in comparison? On top of that, how good does the Japanese release sound? Which is noted to be better than the US re-release.

It would be interesting to get the Midway Laserdisc and a DBXII decoder and test out that Trailer. There are a couple decoders on ebay.
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 26 Jul 2020, 18:05 
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teddanson wrote:
Check your subwoofer at home on the back it should say what it's rated at. Mine is 50hz

Are you sure thats not the input frequency? I had a look at mine today. It says 50/60hz input and then it says 90hz which I think is the crossover frequency. Anyway, my amp is an Onkyo 607 which I bought new in I think 2011. A few years ago the HDMI inputs stopped working. I never bothered to replace it because it was okay for stuff like Laserdisc as it was only processing the sound. After reading this thread, I wanted to hook up my PC over HDMI for testing but It wouldnt work. In the end I found a thread on a forum that said the caps on the board are faulty and need replacing. Sure enough that was the fault. I recapped it today so I can finally use the HDMI inputs again. I played around with a few test tones for the sub using videos like these off youtube. I found my sub went down to 25hz before it became inaudible. It was still pushing air at 5 hz.

Edit: I found a link to the Nov. '74 issue of American Cinematographer that disclord mentioned. It goes in depth about the making of Earthquake. Skip to page 64 to read sepcifically about Sensurround. Download it here.
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 26 Jul 2020, 23:51 
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Gotta contribute the fact that I saw "earthquake" in a little hole in the wall "crap" theater in the late 1970's.

That sensurround billing got alot of commercial hype back at the time.
Damn if it didn't shake the chair I was sitting in.
Seemed like a overdose of distortion and reverberating speaker sub woofer.
Did the trick though, I think they had to paint the interior after that movies run.

I was like 12 at the time.... so no tech review LoL !

Cheers mates
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 27 Jul 2020, 04:20 
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The original pan n scan Earthquake LD has the stereo track with the sensurround encoding but you'd need the original decoder to extract the content out of which few exist in the world. The later widescreen pressing is a faux attempt and just puts rumbly noise in the low end.

Later films used the MOD 2 Sensurround which applied the bass to mono tracks. None of these or Earthquake have ever had their Sensurround versions released and the discs that label it such are false remixes made by universal that are puny in comparison to what they should be. Disclord said the trailer on the Midway LD had sensurround encoded but not the feature.
I've heard of the Rollercoaster German BD but no information as to what's on the disc. Good luck with the hunt!
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 27 Jul 2020, 08:44 
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sdraper wrote:
The original pan n scan Earthquake LD has the stereo track with the sensurround encoding but you'd need the original decoder to extract the content out of which few exist in the world.


Is that the DBXII encoder/decoder that disclord mentioned? The one that decodes the Midway trailer.
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 27 Jul 2020, 11:14 
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firehorse_44 wrote:
Gotta contribute the fact that I saw "earthquake" in a little hole in the wall "crap" theater in the late 1970's.


Those were the best theatres! How I wish I could travel back to 70's and early 80's New York (armed with a Colt 45 and a stab vest given how dangerous the city was back then) and visit the grindhouses even once!

sdraper wrote:
I've heard of the Rollercoaster German BD but no information as to what's on the disc. Good luck with the hunt!


It's apparently on the USA Blu Ray too but has been messed about with. I'll see if I can get the German Blu Ray soon and run a test on it. I would imagine if the real, authentic Sensurround track was being used then you should be able to hear the cue tones on the track which signalled to the sound stage what to actually do at those moments? If the frequency of those tones is known it may then be possible to mute the rest of the audio to bring those marks out?
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 Post subject: Re: A (crap) analysis of the deafening Earthquake Laserdisc
PostPosted: 27 Jul 2020, 18:42 
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sdraper wrote:
The original pan n scan Earthquake LD has the stereo track with the sensurround encoding but you'd need the original decoder to extract the content out of which few exist in the world.

That's funny, I didn't think it was that rare. If you search ebay for "dbx noise reduction" rather than "dbx decoder", there's a whole bunch of results.

Big question is, do you need type 1 or type 2???
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