# So how low does a good movie theater go?



## jdent02

I'm just throwing a burning question I've had for a while out there...

I always see a lot about the use of extreme low frequency effects in modern movies. I have a very hard time believing that commercial movie theaters (even top flight ones) can move enough air to reproduce much in those infrasonic frequencies. People always talk about the bass in movies 'hitting them in the chest', or some similar analogy, but the frequencies that create that effect are a lot higher in the spectrum than they seem. Prior to 1999 or so movies generally didn't have much (or any) information under 30Hz, yet they still 'shook the theater' just fine.

My question is has anybody actually done a frequency analysis of a modern, high end movie theater? Something like an IMAX? What are they actually capable of?

I'm just curious. BTW, I'm posing this question as an unabashed low bass lover.


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## wgmontgomery

I checked online (THX.com and an Imax "site") and could not find ANY specs for frequency response. Both have parameters that dictate background noise, reverberation time etc., but in my brief search I saw nothing that stated that a THX/IMAX theater must produce bass down to x Hz.


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## jdent02

That's pretty much the same thing I run across.

It's amazing how little information there is out there on this kind of thing. And whenever they do interviews with sound mixers they never ask if they can even hear that low stuff on the dubbing stage.


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## tonyvdb

Keep in mind that high SPL at 30Hz is going to rattle the rafters and your chest quite fine. I suspect that most good theaters dont go lower than that because its simply unnecessary.


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## Todd Anderson

Tony, you're right... the last movie I saw (the new Batman) was really cranked... almost too much. You could feel the sound. I hadn't been to an actual movie theater in some time... I have to say, my seat shook several times. Hard to say how low it was hitting tho.

You definitely can hear LFE coming from other theaters at times...


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## JBrax

The wife and I watched the new Batman at our local IMAX and I must say I was impressed. I watch my movies fairly loud and I must admit at times it was almost too loud. The LFE was incredible and I would also like to know what kind of numbers it dipped to.


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## wgmontgomery

I'm now being tempted to smuggle a spectrum analyzer with me the next time I go to a movie. :joke:


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## jdent02

My Batman viewing experience wasn't that good, as the theater either had no subs or a couple of 10 inchers. Everything else was way too loud though.

MI ghost protocol in an imax theater, on the other hand........still get goosebumps remembering how hard the bass hit. But also no idea just how low it was going, as that movie has loud bass all over the spectrum.

Any theater owners or operators on this forum? Or speaker system installers? They ought to know the answer......


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## bluemax_1

Most decent theaters go down to 30Hz. IMAX theaters usually get to 20Hz at -6db. It would take a ridiculous amount of power to hit high SPLs at 10Hz in the cubic volume of a typical theater, much less the single digit Hz region some of us bassheads see with some of the sub options available for home use these days. I can't get enough of that ULF that they seem to be including more and more often in movies today though, and I can only get that with a capable home system when the BD comes out (if some idiot didn't filter the audio like they did with Super 8, and Battleships). 

There's nothing quite like the sensation of those single digit Hz waves rolling through and pressurizing the room in some of these scenes (like the pod scene in WOTW, and several scenes in Wrath Of The Titans).


Max


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## jdent02

What info are you using to determine that super 8 was filtered? To the best of my knowledge the only blu that has been 'proven' to be filtered was master and commander, and that's because it was compared to the older dvd that used a different audio master. Not all movies have heavy subharmonic bass, even modern ones. It depends on the sound mixers, sound designers and director, and without access to the original mix master its impossible to say for sure what was originally there.


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## bluemax_1

jdent02 said:


> What info are you using to determine that super 8 was filtered? To the best of my knowledge the only blu that has been 'proven' to be filtered was master and commander, and that's because it was compared to the older dvd that used a different audio master. Not all movies have heavy subharmonic bass, even modern ones. It depends on the sound mixers, sound designers and director, and without access to the original mix master its impossible to say for sure what was originally there.


SpecLabs audio spectrum analyzer.
http://spectrum-lab.software.informer.com/
http://www.qsl.net/dl4yhf/spectra1.html

Whether a subsonic filter is applied in mixing or mastering, with the multitude of movies out these days with subsonic/infrasonic/ULF content, a scene with a huge multi-ton object bouncing around should have substantial subsonic content. It was terribly disappointing. All the high pitched sounds were ear piercingly loud. 

Sure if the mixers were trying to replicate a train crash and make it realistic, a huge metal object in a crash like that would produce ear piercingly loud metallic sounds, but if you do all that and then castrate the low end? That's ridiculous. I've seen a freight container fall 1-foot to the ground and there I felt the ground tremor. No idea how low or loud that was, but large object impacts produce subsonic content. , I can feel semis drive by.


Max


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## jdent02

bluemax_1 said:


> SpecLabs audio spectrum analyzer.
> http://spectrum-lab.software.informer.com/
> http://www.qsl.net/dl4yhf/spectra1.html
> 
> Whether a subsonic filter is applied in mixing or mastering, with the multitude of movies out these days with subsonic/infrasonic/ULF content, a scene with a huge multi-ton object bouncing around should have substantial subsonic content. It was terribly disappointing. All the high pitched sounds were ear piercingly loud.
> 
> Sure if the mixers were trying to replicate a train crash and make it realistic, a huge metal object in a crash like that would produce ear piercingly loud metallic sounds, but if you do all that and then castrate the low end? That's ridiculous. I've seen a freight container fall 1-foot to the ground and there I felt the ground tremor. No idea how low or loud that was, but large object impacts produce subsonic content. , I can feel semis drive by.
> 
> 
> Max


Fair enough. I agree that train impacts and crashes should contain those kinds of super deep bass frequencies, but if even top flight theaters can't reproduce them, the sound mixers might have figured why bother putting them in there in the first place. Although the sound FX mixer for Super 8 was also responsible for War of the Worlds and Cloverfield, so she is certainly no stranger to high intensity ULF content. What I would give for an opportunity to pick her brains about these kinds of things..... :bigsmile:

I thought you were saying the LFE was filtered for home video release, which I was arguing that there was no proof of. My bad.


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## Tonto

Yea, I'm all for the ULF's, I mean, how many times have you felt your house rattle, followed by the thunder clapping. And that just a simple lightning strike. I love LFE!


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## jdent02

Same here. That's why it's so disappointing when movie theaters skimp on their subs and can't hit 40Hz, much less 30 or 20. And I've been to waaaaay too many theaters where they must turn the subs off as there is NO low end at all.


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## jdent02

Just a random followup..

I ran the Super 8 train crash through Spectrum Lab and I don't think it's been filtered at any point. Most of the high intensity stuff is around 30-50Hz, but there is some really good stuff in the 20-30Hz region on occasion. There's also content extending all the way down to 5Hz but usually at a much lower intensity. It looks pretty similar to most movies out there, with active manipulation and high intensity bass down to about 20Hz, and noticeably lower levels (but still present) below that. Like icing on a cake that the theaters can't reproduce.....


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## pharoah

wgmontgomery said:


> I'm now being tempted to smuggle a spectrum analyzer with me the next time I go to a movie. :joke:


haha do it!im one of the folks who would be curious to know as well.i know the movie i watched in 2009 star trek.it had some awesome bass in the theater.


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## jdent02

wgmontgomery, sounds like you're on the hook for bringing us proof of what movie theaters can do. I suggest Avengers or waiting for the Hobbit, as either of those should be great tests :T


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## Todd Anderson

Has anyone been In a theater - outside of a theme park - that has tactile transducers in the seats??? I don't think I have. But, I read somewhere that some theaters were adopting them...


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## tonyvdb

27dnast said:


> Has anyone been In a theater - outside of a theme park - that has tactile transducers in the seats??? I don't think I have. But, I read somewhere that some theaters were adopting them...


You mean D-Box seats? all the big theaters up here in my city have at least two rows of seating that have them.


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## yoda13

Well, I just came from seeing The Bourne Legacy (free tickets) at one of the local theater and I have to admit that I was pleasantly surprised. I know Empire Theater have been revamping some of their locations. 

Of course, I'm not privied to how low the subs go but I can tell you that it has some output. I was sitting the second row from the top and the vibrations were abundant. The scene where the cabin gets blown was absolutely fantastic. You definitely felt it in your chest. My wife commented "Geez hon, it feels like home"

I couldn't see the brand of the new speakers but I thought I read JBL. I'm going to have to see if I have any friends that would know somebody that could get me "inside":bigsmile:

cheers


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## wgmontgomery

jdent02 said:


> wgmontgomery, sounds like you're on the hook for bringing us proof of what movie theaters can do. I suggest Avengers or waiting for the Hobbit, as either of those should be great tests :T


Oh well, I try to get my laptop inside the next time that I go. :help: It would be _quite_ interesting...IMHO.


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## bluemax_1

yoda13 said:


> Well, I just came from seeing The Bourne Legacy (free tickets) at one of the local theater and I have to admit that I was pleasantly surprised. I know Empire Theater have been revamping some of their locations.
> 
> Of course, I'm not privied to how low the subs go but I can tell you that it has some output. I was sitting the second row from the top and the vibrations were abundant. The scene where the cabin gets blown was absolutely fantastic. You definitely felt it in your chest. My wife commented "moowee hon, it feels like home"
> 
> I couldn't see the brand of the new speakers but I thought I read JBL. I'm going to have to see if I have any friends that would know somebody that could get me "inside":bigsmile:
> 
> cheers


Just FYI, the 'chest slam' region of bass is more in the 50-70Hz region, which most setups can reproduce to adequate levels (except maybe Bose type HTIBs).

Note that the SpecLabs settings make a difference as to how the graphs look. You might be seeing 'noise' in the measurement. Try measuring something like Tron:Legacy or Wrath Of The Titans, or WOTW to see what infrasonic bass looks like. Most folks don't notice the difference of don't find the ULF heavy scenes impressive simply because their setups can't reproduce it so they've never felt it. You don't feel it in commercial theaters because they don't go that low.


Max


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## yoda13

^^^^
Cool. I know most commercial theaters won't have equipment to dig in the ULF region. I was just making comparison as of before the theater did an equipment re haul. Before, it did sound like a Bose HTIB.

I can't say how low some scenes were just by ears, but from a tactile point of view, I would say comfortably that some must have been pretty close to +/- 40Hz region, which is an immense improvement to before. 

cheers


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## Todd Anderson

wgmontgomery said:


> Oh well, I try to get my laptop inside the next time that I go. :help: It would be _quite_ interesting...IMHO.


This just made me chuckle. If you sneak a mic and a laptop into a theater then you deserve to be branded with the "HARDCORE AWARD"

I love the enthusiasm.


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## Todd Anderson

tonyvdb said:


> You mean D-Box seats? all the big theaters up here in my city have at least two rows of seating that have them.



I guess that's what I mean... I wasn't aware that theaters only had certain rows designated like that. How do you even know which seats have it?


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## tonyvdb

the seats are clearly marked and at least here they are high back red seats rather than the standard dark blue or grey material (you pay extra to sit in them). Personally they have them too far back in the theaters, (usually half way back) I like sitting about 1/3 of the way back. But as I have said in another post I have no interest in going any more to the theaters. The cost is crazy and the quality is just sub par.


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## jdent02

I still like the theater experience when it goes well, i.e clean picture, good sound and a polite audience. I don't think I need to elaborate on how rarely those three occur at the same time.......

And yes, the 'chest slam' bass is a lot higher in the spectrum than many people think, which is why people have such fond memories of the first Jurassic Park "shaking the theater" even though there is little bass under 30Hz (and nothing in the true infrasonic regions). A memorable analogy (who someone else came up with) is that the ULF bass levels in Jurassic Park vs. something like Tron Legacy was like the difference between a mosquito fart and an earthquake :heehee:

I have a running theory that the rise of HT gear is the real reason why they quit filtering out bass below 25Hz during mixing. If theaters still can't reproduce it there's no other good reason for it to be there, as it would hog bandwidth from the higher 'slam' frequencies that many theaters can reproduce.


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## bluemax_1

jdent02 said:


> I have a running theory that the rise of HT gear is the real reason why they quit filtering out bass below 25Hz during mixing. If theaters still can't reproduce it there's no other good reason for it to be there, as it would hog bandwidth from the higher 'slam' frequencies that many theaters can reproduce.


Yep, I'd say that's a pretty accurate assessment. If you trace the timeline of soundtracks with ULF, it doesn't go back very far (relatively speaking). The 2 big factors were, as you surmised the fact that more HT setups are becoming capable of reproducing this content, and the advent of digital effects tools making it much easier to create said content (from someone in the film audio mixing industry).

I have to say, I really like it. An example in a recent discussion was about the Transformers movie. In real life, you would expect a gigantic multi ton robot simply walking nearby to produce significant ULF content that you could feel. The first Transformers movie was good about replicating this (Real Steel wasn't too bad either with some scenes, like the first glimpse of Zeus). In contrast, seeing a huge mechanical object stomping about without the ULF content reduces the realism.

The audio mixers for Underworld:Awakening understood the concept too, (although realistically, they may have exaggerated it with the Super Lycan to emphasize its size).

In stark contrast, the destruction of Hometree in Avatar had no ULF content to speak of. This is a falling object the size of a skyscraper, and unlike a skyscraper, it doesn't break up into lots of pieces while falling. The main trunk of a tree stays intact while falling. If anyone's been nearby when a fairly large tree has been felled, you would have noted that even a tree a fraction the size of the tree in Avatar creates significant ULF when it hits the ground. The notable absence of it was obvious to all of us ULF fans (as was the absence of it in Super 8 for the train crash).


Max


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## jdent02

Avatar seems to be a really sore spot in the basshead community, and I have to agree that it does seem a bit underwhelming. The funny thing is that there is ULF content in the movie that goes pretty deep, but it's at a very low volume and not really noticeable. Even in the theater I noticed that the bass really didn't 'hit' much. I thought it was the theater but I saw Ghost Protocol in the same auditorium and the low end there nearly snapped my head off.

Funny thing is both Super 8 and Avatar were mixed and/or sound designed by people who traditionally mix with lots of ULF (Anna Behlmer and Christopher Boyes, respectively).


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## Prof.

If anyone has ever wondered what subs are behind the screen in commercial theatres..This is what they look like...http://www.krix.com.au/Product/Detail.aspx?p=45&id=52

Krix manufacture and supply most theatres in the Southern hemisphere, as well as many others world wide..
In most theatres they use between 4 & 8 of these twin 18"s..Hence why you can feel the bass in your chest!!


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## jdent02

The tech specs say it all: 25Hz lower limit. While I'm sure it has output below that, it probably wouldn't do much in the infrasonic realm.

Still, I want one :bigsmile:


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## bluemax_1

jdent02 said:


> The tech specs say it all: 25Hz lower limit. While I'm sure it has output below that, it probably wouldn't do much in the infrasonic realm.
> 
> Still, I want one :bigsmile:


These days, I don't have a lot of faith in measurements without ranges, i.e. +/-3db. Too many manufacturers like to make their products sound better to the unitiated (remember PMPO power ratings?). For eg.Goldenear's claims of output to 18Hz for their Triton IIs. Those things fall off a cliff below 40Hz. I don't know what they're doing at 18Hz, but it's not enough to give a mouse a decent massage.

Those subs are ported, meaning (as with most commercial subs) they're made for quite a lot of output above 30-35Hz, but rolloff pretty quick below the port tuning (which I would assume is higher than 25Hz, or they would advertise that it was flat +/-3db down to 25Hz ground plane or some such).

I'll stick to good sealed subs.


Max


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## wgmontgomery

27dnast said:


> This just made me chuckle. If you sneak a mic and a laptop into a theater then you deserve to be branded with the "HARDCORE AWARD"
> 
> I love the enthusiasm.


 I don't go very often; I haven't been to a theater since the last Harry Potter film. I will, however, try to get in with my laptop and mic when I go. *If *my girlfriend will put them in her pocketbook it should be easy enough. Also, I usually go to the matinée to _avoid the crowds _and save money.


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## bluemax_1

wgmontgomery said:


> I don't go very often; I haven't been to a theater since the last Harry Potter film. I will, however, try to get in with my laptop and mic when I go. *If *my girlfriend will put them in her pocketbook it should be easy enough. Also, I usually go to the matinée to _avoid the crowds _and save money.


LOL, I can just imagine, "Hey! You're not allowed to record in here, bootlegging is a crime!".

With straight face:
"I am not bootlegging. This is not recording equipment per se, it is measuring equipment. I am analyzing your audio system. Would you like to know how your theater's sound system ranks? I can also tell you where you could make improvements".


Max


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## wgmontgomery

bluemax_1 said:


> LOL, I can just imagine, "Hey! You're not allowed to record in here, bootlegging is a crime!".
> 
> With straight face:
> "I am not bootlegging. This is not recording equipment per se, it is measuring equipment. I am analyzing your audio system. Would you like to know how your theater's sound system ranks? I can also tell you where you could make improvements".
> 
> 
> Max


:rofl: It _might_ be a bit hard to explain. :duh:


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## jdent02

Just use a lot of big words like 'x-curve adherance', 'ULF extension', 'max peak dB', 'noise floor', etc.....

My guess is the teenagers that work at these theaters will just tune out at some point and you can walk right past them. :T


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## wgmontgomery

jdent02 said:


> My guess is the teenagers that work at these theaters will just tune out at some point and you can walk right past them. :T


Hey! I was once one of those teenagers! :rofl: I saw must have seen _The Karate Kid*_ and _Revenge of the Nerds_ 50 times.

*_The Karate Kid_ is actually a very good movie (for what it is)...IMHO. I used the "wax on, wax off" to help remember chiral compounds in Organic Chemistry.


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## tonyvdb

wgmontgomery said:


> *_The Karate Kid_ is actually a very good movie (for what it is)...IMHO. I used the "wax on, wax off" to help remember chiral compounds in Organic Chemistry.


Absolutely a classic! I recently rewatched the DVD series with some friends and enjoyed every one.


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## wgmontgomery

tonyvdb said:


> Absolutely a classic! I recently rewatched the DVD series with some friends and enjoyed every one.


My favorite line in the movie has to be, "So why learn Karate?" "So we don't have to fight." Also, in the same scene, "Danielson, you are wet behind the ears." :sn: I guess I'll see how well I remember the dialog.


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## ranbunctious

Back in the 70's, there was a sensation called 'sensurround' tracks added to movies like Earthquake and Midway. These Cerwin Vega folded horn subs had to be removed because the older movie theaters were losing bricks from the stress. Cerwin Vega still makes these subs under the Earthquake name. It's the BIGGEST and BADDEST bass you can possibly get.


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## bluemax_1

ranbunctious said:


> Back in the 70's, there was a sensation called 'sensurround' tracks added to movies like Earthquake and Midway. These Cerwin Vega folded horn subs had to be removed because the older movie theaters were losing bricks from the stress. Cerwin Vega still makes these subs under the Earthquake name. It's the BIGGEST and BADDEST bass you can possibly get.


Are you sure your info is correct?

Yes, the movie 'Earthquake' was definitely the first use of special subwoofers specifically aimed at reproducing lower octaves than the average theater, but I thought the frequency bandied around was 19Hz.

I don't recall what subs they used, but I'm very familiar with the Cerwin Vega EL-36 Earthquake. We used those for pro-sound reinforcement. Those puppies, like most of the commercial sub offerings used in theaters (and nightclubs) don't do much at all below 30Hz. The Earthquake sub's -3db point is 39Hz and is -10db at 33Hz. Below 30Hz, it's off a cliff. It's been superceded first, by the 'Afterburner', and now, by the 21" driver TS-42, which while being able to output ridiculous levels at 80Hz, still falls of a cliff below 30Hz.

I will say though, folded horns will produce prodigious volume at the frequencies they do well. I remember a rave outside Chicago city limits. It was setup in the field of a racing paddock with 4 separate areas; the main stage and 3 smaller stages. One of the smaller stages had 4 folded horn subs that could be heard over the main stage's 16 dual subs. This was out in the open too.

The thing is, for most music (especially pop/commercial music), there's no real need to delve below 30Hz, with the exception of pipe organs and newer subterranean dubstep (where the makers use similar tools as movie effects folks, to create insane bass tones down even to 1 - 3Hz.

As mentioned, it takes a LOT of displacement to produce infrasonic content at appreciable levels, requiring either a lot of sealed subs or something like a Thigpen Rotary (capable of high output down to 1Hz). One of the movie sound mixing stages once used an array of Bag End Infrasubs. These subs can play down to ~7Hz, the mixing stage has since moved to other subs with more headroom above 30Hz, but without infrasonic capability.

Should I be lucky enough to win the lotto, I'll be building an HT with a Thigpen Rotary to scare the neighbours (seismologists conducted testing with a Thigpen Rotary mounted in a large U-Haul type truck where the infrasonics produced were picked up by seismic equipment miles and miles away).


Max


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## ranbunctious

You are correct. An earlier post from another member stated the effect was 5Hz. After checking this website, the actual number was 16 Hz. This is pretty interesting reading:

http://en.wikipedia.org/wiki/Sensurround


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