Sound in the Cinema

this thread actually started elsewhere:

Me said:
>BTW: one of my many jobs is overseeing (which at the moment means doing everything) the design of some superior cinema sound systems for HD3D Movies so i do have some background.

Bill F. said:
Dave,

You've piqued my interest. Sounds like cutting-edge stuff (although they didn't give the audio end any playtime on the website).

It is early days, most of the stuff is in my head (or internal papers i have generated). The concepts for what we want to do is much that same as when i 1st formulated it some 15 yrs ago -- the big difference is that a lot of the stuff we need is now off-the-shelf instead of millions of dollars of development away.

Since you're a guy who might know, let me ask you this: Do you see any current/growing/future demand in modern theater-land for extreme sub-bass reproduction? I understand that current movie bass content doesn't really go south of 20Hz. However, I'm wondering if that is changing as movies push the limits and try to keep wowing viewers. It seems to me that, say, a decently loud 12Hz effect on a movie bass track could give movie producers a whole new palette of psychological tools to get through to viewers (while simultaneously challenging theater architects!).

Backgrond 1st:

The need to upgrade the cinema to a level where it gives a better and different experience than the home theatre is essential to keeping the exhibition sector well. The industry is at a cusp with the switch from Analog to Digital that will see a lot of change. The change on one end is being slowed by the momentum of a cash-flow challenged and very conservative exhibiton sector and on the other end by the clear advantages in terms of keeping costs down (and opening it up to new filmmakers -- a kid with a DV cam & an iMac can be making decent movies bringing in much needed new blood), streamlining the process, and opening up whole new areas of creative possibilities.

There is little incentive for broke theatre owners to upgrade their infrastructure for digital since it, as yet, produces stuff that is only on par with current analog that they have already paid for. We hope that HD3D -- which is only possible with the new digital tech -- will provide a compelling killer ap for the movement to digital.

Now your specific question:

One has to be very careful with going too low, since it can induce nausea in some people and if too low even psudeo-epileptic fits. Even excluding potential lawsuits, you don't want to have customers staying away because they don't want to put up with getting sick to see a movie. With the increased realism of 3D we already have some issues to deal with, and semi-jokingly talk about barf-bags under the seat and "so real you wish you were somewhere else".

That caveat aside, we have a lot of prototyping to do, and i expect we will have at least three levels of quality in the sound systems. The hi-end one is the one that generates the most excitement, and we envision floor-to-ceiling line sources with elecro- or magneto- stats (the 3dB drop per doubling being a driver here) coupled with very large bass horns (17-20 Hz cutoff) built into the floor or walls -- this is where Nick's field coils get me hot. Amplification will be 1st class (at least Brystons) and may even use vacuum state technology and will be high data-rate digital until the D/As (either justr before or in the amps -- digital amps seem to be making good progress).

The big thing, at least in our own movies, that will contribute greatly to improved sound quality will be very tight control from the time it enters the mic to when it leaves the speakers.

I am anticipating that movie bass tracks will creep steadily deeper over the coming years, and I'm dreaming that I'll be the guy to anticipate and fill that bottom niche. What's your take on where movies are and where they're going? More to the point, do you anticipate a market for such a device?

You probably are thinking in the right direction -- i doubt most cinema systems now actually get down to 40 Hz. And if you don't find a market in cinema, there is certainly a market in the growing special venue market.

dave
 
i am glad to help...

Well as you know planet10 that subs are what I am knowable in….
I do no see any audio tracks in the near future to go below 20Hz…
As you might know it is hard enough to find a good sub driver that will do 20Hz well let allow 12Hz… my opinion on this is one of a negative response. I do not see movie or music makers encoding tracks with frequencies south of 20Hz just on the basis that not many people have equipment to handle that low of frequencies. I believe that it would not necessarily enhance the movie experience anymore then a high quality theater system already does.
Well that’s my take on it anyway

Slice:D
 

Bill F.

Member
2001-11-15 5:25 pm
SW MI
Hey, thanks Slice! :):):);)

Well, Dave, your push toward the future sounds facinating. As you've probably noted, there is impetus for improvement from the grassroots up (people are less and less tolerant of shabby theaters) and from the top down (George Lucas, et al embracing a 100% digital chain). I think it'll be a fun ride.

Your theatre sound systems are pretty ambitious. (I love going to Omnimax movies and seeing the kit behind the screen when they backlight it.) Are you planning to push this as a turnkey package to enforce conformity or just as a rigorous set of standards? It certainly sounds like much of the hardware will be propriatary. Is that going to be a big financial pill for franchisees to swallow?

Regarding the physiological effects of sub-bass, I followed the "brown note" thread with interest. Perusing the links, I didn't come across dire warnings of profound effects. Do you have any other info on this? the worst I read about was mild queezyness and tickling. Tom Danley talks about working on a 10Hz piston-driven horn that visibly shivered every leaf and blade of grass in the area. Oh well, I suppose there are always those extra-sensitive people...

I envision deep, clean sub bass to be a very useful tool for producers. Though inaudible, it creates a palpable sense of foreboding, dread, and power that you can turn off and on at will.

I'm curious--What are some examples of "special venues?" you referred to?

Bill
 
Bill F. said:
Your theatre sound systems are pretty ambitious. (I love going to Omnimax movies and seeing the kit behind the screen when they backlight it.) Are you planning to push this as a turnkey package to enforce conformity or just as a rigorous set of standards? It certainly sounds like much of the hardware will be propriatary. Is that going to be a big financial pill for franchisees to swallow?

It will no doubt be a careful mix. Most of the exhibition end cannot swallow the cost, but fortuneatly biggies like Tehnicolor & Boeing are stepping up to fund the transition.

Regarding the physiological effects of sub-bass, I followed the "brown note" thread with interest. Perusing the links, I didn't come across dire warnings of profound effects. Do you have any other info on this? the worst I read about was mild queezyness and tickling. Tom Danley talks about working on a 10Hz piston-driven horn that visibly shivered every leaf and blade of grass in the area. Oh well, I suppose there are always those extra-sensitive people...

Most of our, admittedly sketchy, data comes from the effects the 17 Hz system installed for some showings of Earthquake.

I envision deep, clean sub bass to be a very useful tool for producers. Though inaudible, it creates a palpable sense of foreboding, dread, and power that you can turn off and on at will.

Certainly an area for exploration -- i expect you would have no end of vollenteer subjects.

I'm curious--What are some examples of "special venues?" you referred to?

Probably best exemplified by the "ride films"... Back to the Future, Terminator 3D, Spiderman, Captain Eo...

dave
 

Bill F.

Member
2001-11-15 5:25 pm
SW MI
Servodrive

we envision floor-to-ceiling line sources with elecro- or magneto- stats (the 3dB drop per doubling being a driver here) coupled with very large bass horns (17-20 Hz cutoff) built into the floor or walls

Dave,

You're probably already familliar with this stuff, but I thought I'd mention that Servodrive/Sound Physics Labs products could be an almost turnkey solution for your loudspeaker needs. (I'm not affiliated with either, just an admirer of both.)

In particular, SPL's unity horns seem to have many attractive qualities. Their phase linearity and constant directivity dispersion pattern suits them well to line arrays. Multiamped unity horn line arrays would give you excellent intelligibility and shading control.

The unity horn's low cutoff should mate well with Servodrive's BassTech 7 bass horns. They claim to be flat to below 28Hz (freespace groundplane, I think). Arraying them, extending the mouth flare, or archetecturally loading them should extend their indoor response down to 20Hz, IMO.

Now that would be the way to hear a movie!

Bill
 
Re: Servodrive

Bill F. said:
Servodrive/Sound Physics Labs products

Already looking at the BassTech 7s on the bottom... the Unity type horns are in a fall-back position if we don't get the line arrays to do what we want. I never really considered using them as a line array.... not sure that the stacked discreet source would give the coherency we are looking for.

dave
 
Bill,
In particular, SPL's unity horns seem to have many attractive qualities. Their phase linearity and constant directivity dispersion pattern suits them well to line arrays. Multiamped unity horn line arrays would give you excellent intelligibility and shading control.

Oh yes, may i contribute some listening experience with the Unity horn?

It is a horn sonically, no question. Sound is, well, a bit forward, hits you considerably. But compression distortion is few and goes never beyond that limit leading to long-term listening fatigue. Very smooth, very musical, very open. Imaging is great. Dispersion is not completely perfect but no issue of complaint either. You can be in the room where you want and still have atleast medium-to-good imaging.

A cinema equipped with Unitiies and those servomotor-driven bass horns? And maybe tube electronics?
Gorgeous!!

In Munich we have a wonderful cinema called Cinema; they preferably play movies in OL. Best modern style cinema i know by far. But it does not come near sonically to the old-fashioned cinema equipped with horns and tube electronics i had the opportunity to try out near Leipzig (shortly after the German Democratic Republic ceased to exist).
And particularly not concerning speech intelligibility.
And it does not come near sonically to the 5 channel system equipped with 2way and 3way Avantgarde Audio tractrix horns I liistened to 2 years ago at the AES convention Munich.

Horns and tube gear for cinema !! WhooooopWhooop! :)
 

SteveG

Account Disabled
2002-01-07 7:20 pm
Newton Falls, Ohio
Well, I'm jumping into this thread right in the middle, so forgive me if I am not completely on topic.
I recently went to see an omnimax movie at the Great Lakes science center, and the sound was pretty impressive. Here is a description from their web site:

High-fidelity, six-channel sound by SONICS has four screen channels and two surround channels. The sound track of an OMNIMAX film is on a separate tape or digital disc because there is no room on the film for an audio strip. A computer keeps the sound system synchronized. The Cleveland Clinic OMNIMAX Theater has full digital capabilities for sound, which provides wider audio
frequency range with less distortion and coloration. 11,600 watts of audio power is delivered through 44 speakers in seven clusters. Six clusters of speakers each contain four 12-inch woofers, one mid-frequency horn and one high-frequency horn. The seventh cluster
contains eight 18-inch subwoofers. Each cluster is a "three-way speaker system," meaning sound is sent to three different types of speakers, depending on the frequency of sound. Sub-bass is a "fourth way." Sub-bass frequencies are pulled from all six audio channels and sent to the sub-bass speakers. Speakers are located behind the domed screen. Six digital, programmable, one-third octave equalizers provide customized audio control for the unique environment for the OMNIMAX theater.

The sound was very clear, and the dynamic range was excellent, as you could imagine. The picture, on the other hand, was not all that great. It was just too damned big! It made your head hurt, and it was somewhat grainy, imho. Just thought I would recommend anyone who hasn't been to one of these to check it out, even if just for the sound.
Steve
 

Bill F.

Member
2001-11-15 5:25 pm
SW MI
My (limited) understanding of prosound line array theory is that successful line integration has largely to do with even polar response of each segment so that you can steer each to predictably and constantly illuminate a particular coverage area. That's why I was suggesting the constant directivity and point-source characterics of Unity modules should lend them to line arrays.

The advantage I was suggesting with multiamping is that you could taper the array output down toward the bottom to get even SPL from front rows to back, effectively building on the 3dB decay advantage arrays already give you.

Let me know if I'm off base here :).

Bill
 

Bill F.

Member
2001-11-15 5:25 pm
SW MI
Hey Dave,

How goes the fight? Curious to hear the latest about HD3D...

For my part, I'm still doing my best to push the limits. Got a hot new sub concept on the drawing board for your bottom octaves. >3500 ci of one-way displacement in a 16 cu. ft. package. Conservatively, I believe that works out to >130dB groundplane @ 12Hz. Uses a simple trick to bend hoffman's iron law, so efficiency is high and Fb is low, too. Sounds improbable, I know. Hear me now and believe me later. :smash:

I don't mean to tease, I'm just excited about the possibilities. Back to the laboratory with me now...