There are many on indietalk who have or aim to have their films screened in theatres, either hoping or working towards possible theatrical distribution or more commonly aiming for a theatrical screening at a film festivals. Much has already been posted on indietalk about creating sound for theatrical screening and many profess to take sound seriously, in practise this does not appear to be true. While many on indietalk appear to be well clued up on resolutions, aspect ratios and other technical specifications of their cameras and projection of their visuals, almost no one appears to know or understand the basics of sound systems in general and of theatrical sound systems in particular. This appears to have lead some/many down the road of misunderstanding and misinformation due to assumptions which are incorrect. I'm creating this post as a reference, something we can link back to when discussing issues of theatrical sound. I'll explain the basics of theatrical sound systems and how they differ from consumer and even professional monitoring sound systems:
I'm only going to write a few sentences on acoustics, even though room acoustics is the defining factor of any sound system. Modern cinemas are carefully constructed from the ground up to minimise acoustic problems which all enclosed spaces cause. This is achieved firstly by using room ratios of height, width and depth during construction which have been proven to reduce acoustic problems and then after structural work is completed with acoustic treatments to reduce sound reflections, reduce phase interference and provide the audience hopefully with uncoloured and detailed audio playback. Old cinemas were not constructed with such attention to acoustic properties because until the late 1970s theatrical sound systems were mainly mono but to cope with the modern multi-channel film standards (5.1, 7.1, etc.) these older theatres have at some stage required some serious specialist treatment to reduce their acoustic issues.
Now to the sound systems themselves, with hardly any exceptions cinemas employ at least 5.1 surround systems and quite frequently 7.1 or even one of the newer kids on the block like Dolby Atmos. Home cinema systems can now be purchased for a few hundred bucks which also provide 5.1 surround, the implication of the name (home cinema system) and use of Dolby Digital implies that these systems are essentially the same as a theatrical sound system, just cheaper and smaller to fit in a home environment but this implication is not the reality. Lets look at some of the differences. A cheap home system will consist of 5 satellite speakers, each usually with a 2" or 4" driver for the mid frequencies and a 1" dome tweeter to reproduce the high frequencies. These satellite speakers are placed in the Centre, Front Left, Front Right, Left Surround And Right Surround positions relative to the screen and listener/s but do not reproduce any bass frequencies. All the bass frequencies are redirected to another speaker type (a sub woofer) which will have a larger driver, usually 6" or 8" to recreate the bass frequencies. This keeps the costs of the system down, as having a 6" - 8" bass driver on each of the satellite speakers would drastically increase their size and the complexity of their design and cost exponentially more. This is called a bass managed system as all the bass frequencies below the crossover, the point at which the frequencies which should be sent to the satellite speakers are re-directed to (managed by) the sub woofer. On a small cheap home cinema system this crossover would likely be at 120Hz and the sub would be reproducing all the film's low frequency content from 120Hz down to about 40Hz. Spending a considerable amount on a home cinema system or even a "professional" 5.1 monitoring system, say several thousand dollars, will improve the situation considerably. The dome tweeters of the satellite speakers in this expensive system will have more accuracy and power but not be vastly different from a cheap system, the mid frequency drivers though will be much higher quality and considerably larger 6" - 8" usually and there may be more than one mid driver. These satellite speakers can reproduce more power, more accuracy and lower frequencies than our cheap system. The crossover of our expensive system is going to be 80Hz or in some cases 60Hz. The sub woofer is also going to be significantly larger, more powerful and have a more efficient acoustic design, with a 10" or possibly 12" driver and able to reproduce frequency content down to around 30Hz or so and possibly as low as 20Hz (but with lower power and less accuracy at this limit). The only real difference between a consumer system and "professional" monitors when we get into the several thousand dollar range is a difference in design emphasis. A home system will likely have more emphasis on the visual appearance and be designed to sound good, whereas with a monitoring system the visual appearance is secondary to the functional acoustic design requirements and the emphasis is on accurate sound reproduction rather than subjectively "good" or "nice" sound reproduction.
OK, so now on to theatrical systems. First of all, cinema owners don't really go out and buy a theatrical sound system as you would a home or monitoring system. The acoustics have been designed by a specialist and a sound system is specified for those acoustics. Of course, cinemas vary considerably in size and there are competing theatrical sound system manufacturers. The components of the sound system are chosen for each cinema individually and are therefore effectively always custom sound systems, installed by the manufacturers themselves or qualified installers. Once installed and hooked up to the cinema sound processors, the system is tested, fine tuned and calibrated.
The speakers themselves are significantly different to home cinema and "professional" monitoring systems. To start with dome tweeters for the high frequencies are never employed as they cannot output the power or directionality of sound required in a cinema so high power horn type compression drivers are used instead. For the mid frequencies 8" high power drivers are quite common, at least a pair of them or four in an array, although a single extremely high powered driver is used by some manufacturers. Each individual speaker array is completed with some low frequency drivers, commonly two or three 15" - 18" drivers. It's not uncommon for the mid drivers to also be housed in a horn array to provide better directionality. Here's a pic of a typical theatrical screen speaker array, of which there are at least 3 in every cinema. They are not pretty, they are purely functional as prettiness is irrelevant due to the fact they are hidden behind the acoustically transparent screen anyway. To give you some idea of scale, this speaker is about 9ft (2.7m) high and each of those bass cones are 18" in diameter.
Theatrical sound systems are not bass managed as are home cinema and professional 5.1 monitoring systems, with their huge bass drivers they easily output more accurate and powerful sound than even an expensive 5.1 monitoring system and don't forget there are at least 3 such speakers behind the screen, so at least 6 of these of these large bass drivers compared to the one relatively small bass driver in a bass managed system. Theatrical sound systems still have sub woofers but these subs are in addition to the full range screen speakers and are not there to handle the low frequencies which the screen speakers cannot reproduce. These subs are usually very similar to the low frequency drivers in the screen speakers and arrays of 4-8 sub woofer units are usual in modern multiplex cinemas, each one housing two 15"-18" drivers.
The surround speakers are also significantly different from home cinema or 5.1 monitoring systems. Look around your local cinema and you won't see two big speakers in the Left and Right surround (Ls, Rs) positions. What you'll see is 10-30 or so relatively small speakers spaced all the way around the side and rear walls of the cinema pointing down towards the audience. There are no specific Ls or Rs speakers in a theatrical system, instead a processor is feeding each speaker with various percentages of the audio which is in the Ls and Rs audio channels and for those speakers on the side walls near the screen also some of the front L and R audio channels. There's a good reason for this: To get an accurate image from a 5.1 system the audience really needs to be sitting in the "sweet spot", the centre of the cinema. Obviously, the majority of the audience are not going to be sitting in the centre of the cinema and this array of speakers around the walls serves to diffuse the sound field and effectively make the "sweet spot" much larger. It would obviously be far more difficult and expensive to buy and install banks of these diffuser speakers all the way around the walls with large heavy 15"-18" bass drivers in them, so these speakers don't incorporate large bass drivers and do not usually reproduce frequencies below about 60Hz to 70Hz. These speakers are bass managed and therefore another bank of sub woofers are required somewhere else in the cinema (at the back of the cinema most commonly).
Looking at the power outputs of 5.1 systems is also a bit of an eye opener. A cheap home cinema system will have 5 satellite speakers probably producing around 20w each, plus a sub outputting maybe 40w - 60w. A total of 150w or so of power. Upping the price significantly, into the thousands of dollars, also ups the accuracy and power output. The output of a professional 5.1 monitoring system or high quality home cinema system is likely to be in the 600w-900w range. Spend $20k or so on a very high quality 5.1 professional system and it's going to sound great (provided the acoustics have been taken care of), with maybe twice the power of a quality home system or pro 5.1 monitoring system, say 1,400w or so. So this should be getting us pretty close to a theatrical sound system yes? Nope, not even close, not even in the same ball park!! To start with, you've got substantial differences in the sound characteristics of the different driver types used in cinema sound speakers, a completely different approach to handling all the bass frequencies and a completely different approach to the sound field, particularly the surround channels using the diffuser speakers. Now add to this the fact that a mid sized theatre, say a 300 or so seater multiplex theatre, is likely to have a sound system which outputs somewhere in the region of 30,000w. Compared to this, even a relatively expensive "professional" 5.1 monitoring system is little more than a toy and even a moderate quality home cinema system is considerably less than a toy!
I hear you asking, if a professional 5.1 monitoring system is no more than a toy, why is it called a "professional" monitoring system? It's partly marketing but not entirely, one of these professional 5.1 monitoring systems might be well suited to producing professional mixes for TV broadcast or DVD. They are also used by professionals in the film industry, in sound editing suites for example but they are NEVER used in theatrical mix rooms (dub stages). Accepting the fact that consumer and "professional" 5.1 monitoring systems are so completely different to theatrical sound systems, to mix a film requires an actual cinema sound system, ultimately there's no getting around that fact and believe me, people have been trying for years. You also can't stick a theatrical sound system in your basement or bedroom, despite the fact it wouldn't physically fit and would cost well over $100k, you'd only be able to enjoy the sound in such a small room for a second or so before your ear drums exploded and your liquefied brains ran out of your nose. You wouldn't have to worry about the mess though, the sheer physical power of the sound waves the system could produce would probably reduce your house to a pile of rubble anyway!
G
I'm only going to write a few sentences on acoustics, even though room acoustics is the defining factor of any sound system. Modern cinemas are carefully constructed from the ground up to minimise acoustic problems which all enclosed spaces cause. This is achieved firstly by using room ratios of height, width and depth during construction which have been proven to reduce acoustic problems and then after structural work is completed with acoustic treatments to reduce sound reflections, reduce phase interference and provide the audience hopefully with uncoloured and detailed audio playback. Old cinemas were not constructed with such attention to acoustic properties because until the late 1970s theatrical sound systems were mainly mono but to cope with the modern multi-channel film standards (5.1, 7.1, etc.) these older theatres have at some stage required some serious specialist treatment to reduce their acoustic issues.
Now to the sound systems themselves, with hardly any exceptions cinemas employ at least 5.1 surround systems and quite frequently 7.1 or even one of the newer kids on the block like Dolby Atmos. Home cinema systems can now be purchased for a few hundred bucks which also provide 5.1 surround, the implication of the name (home cinema system) and use of Dolby Digital implies that these systems are essentially the same as a theatrical sound system, just cheaper and smaller to fit in a home environment but this implication is not the reality. Lets look at some of the differences. A cheap home system will consist of 5 satellite speakers, each usually with a 2" or 4" driver for the mid frequencies and a 1" dome tweeter to reproduce the high frequencies. These satellite speakers are placed in the Centre, Front Left, Front Right, Left Surround And Right Surround positions relative to the screen and listener/s but do not reproduce any bass frequencies. All the bass frequencies are redirected to another speaker type (a sub woofer) which will have a larger driver, usually 6" or 8" to recreate the bass frequencies. This keeps the costs of the system down, as having a 6" - 8" bass driver on each of the satellite speakers would drastically increase their size and the complexity of their design and cost exponentially more. This is called a bass managed system as all the bass frequencies below the crossover, the point at which the frequencies which should be sent to the satellite speakers are re-directed to (managed by) the sub woofer. On a small cheap home cinema system this crossover would likely be at 120Hz and the sub would be reproducing all the film's low frequency content from 120Hz down to about 40Hz. Spending a considerable amount on a home cinema system or even a "professional" 5.1 monitoring system, say several thousand dollars, will improve the situation considerably. The dome tweeters of the satellite speakers in this expensive system will have more accuracy and power but not be vastly different from a cheap system, the mid frequency drivers though will be much higher quality and considerably larger 6" - 8" usually and there may be more than one mid driver. These satellite speakers can reproduce more power, more accuracy and lower frequencies than our cheap system. The crossover of our expensive system is going to be 80Hz or in some cases 60Hz. The sub woofer is also going to be significantly larger, more powerful and have a more efficient acoustic design, with a 10" or possibly 12" driver and able to reproduce frequency content down to around 30Hz or so and possibly as low as 20Hz (but with lower power and less accuracy at this limit). The only real difference between a consumer system and "professional" monitors when we get into the several thousand dollar range is a difference in design emphasis. A home system will likely have more emphasis on the visual appearance and be designed to sound good, whereas with a monitoring system the visual appearance is secondary to the functional acoustic design requirements and the emphasis is on accurate sound reproduction rather than subjectively "good" or "nice" sound reproduction.
OK, so now on to theatrical systems. First of all, cinema owners don't really go out and buy a theatrical sound system as you would a home or monitoring system. The acoustics have been designed by a specialist and a sound system is specified for those acoustics. Of course, cinemas vary considerably in size and there are competing theatrical sound system manufacturers. The components of the sound system are chosen for each cinema individually and are therefore effectively always custom sound systems, installed by the manufacturers themselves or qualified installers. Once installed and hooked up to the cinema sound processors, the system is tested, fine tuned and calibrated.
The speakers themselves are significantly different to home cinema and "professional" monitoring systems. To start with dome tweeters for the high frequencies are never employed as they cannot output the power or directionality of sound required in a cinema so high power horn type compression drivers are used instead. For the mid frequencies 8" high power drivers are quite common, at least a pair of them or four in an array, although a single extremely high powered driver is used by some manufacturers. Each individual speaker array is completed with some low frequency drivers, commonly two or three 15" - 18" drivers. It's not uncommon for the mid drivers to also be housed in a horn array to provide better directionality. Here's a pic of a typical theatrical screen speaker array, of which there are at least 3 in every cinema. They are not pretty, they are purely functional as prettiness is irrelevant due to the fact they are hidden behind the acoustically transparent screen anyway. To give you some idea of scale, this speaker is about 9ft (2.7m) high and each of those bass cones are 18" in diameter.
Theatrical sound systems are not bass managed as are home cinema and professional 5.1 monitoring systems, with their huge bass drivers they easily output more accurate and powerful sound than even an expensive 5.1 monitoring system and don't forget there are at least 3 such speakers behind the screen, so at least 6 of these of these large bass drivers compared to the one relatively small bass driver in a bass managed system. Theatrical sound systems still have sub woofers but these subs are in addition to the full range screen speakers and are not there to handle the low frequencies which the screen speakers cannot reproduce. These subs are usually very similar to the low frequency drivers in the screen speakers and arrays of 4-8 sub woofer units are usual in modern multiplex cinemas, each one housing two 15"-18" drivers.
The surround speakers are also significantly different from home cinema or 5.1 monitoring systems. Look around your local cinema and you won't see two big speakers in the Left and Right surround (Ls, Rs) positions. What you'll see is 10-30 or so relatively small speakers spaced all the way around the side and rear walls of the cinema pointing down towards the audience. There are no specific Ls or Rs speakers in a theatrical system, instead a processor is feeding each speaker with various percentages of the audio which is in the Ls and Rs audio channels and for those speakers on the side walls near the screen also some of the front L and R audio channels. There's a good reason for this: To get an accurate image from a 5.1 system the audience really needs to be sitting in the "sweet spot", the centre of the cinema. Obviously, the majority of the audience are not going to be sitting in the centre of the cinema and this array of speakers around the walls serves to diffuse the sound field and effectively make the "sweet spot" much larger. It would obviously be far more difficult and expensive to buy and install banks of these diffuser speakers all the way around the walls with large heavy 15"-18" bass drivers in them, so these speakers don't incorporate large bass drivers and do not usually reproduce frequencies below about 60Hz to 70Hz. These speakers are bass managed and therefore another bank of sub woofers are required somewhere else in the cinema (at the back of the cinema most commonly).
Looking at the power outputs of 5.1 systems is also a bit of an eye opener. A cheap home cinema system will have 5 satellite speakers probably producing around 20w each, plus a sub outputting maybe 40w - 60w. A total of 150w or so of power. Upping the price significantly, into the thousands of dollars, also ups the accuracy and power output. The output of a professional 5.1 monitoring system or high quality home cinema system is likely to be in the 600w-900w range. Spend $20k or so on a very high quality 5.1 professional system and it's going to sound great (provided the acoustics have been taken care of), with maybe twice the power of a quality home system or pro 5.1 monitoring system, say 1,400w or so. So this should be getting us pretty close to a theatrical sound system yes? Nope, not even close, not even in the same ball park!! To start with, you've got substantial differences in the sound characteristics of the different driver types used in cinema sound speakers, a completely different approach to handling all the bass frequencies and a completely different approach to the sound field, particularly the surround channels using the diffuser speakers. Now add to this the fact that a mid sized theatre, say a 300 or so seater multiplex theatre, is likely to have a sound system which outputs somewhere in the region of 30,000w. Compared to this, even a relatively expensive "professional" 5.1 monitoring system is little more than a toy and even a moderate quality home cinema system is considerably less than a toy!
I hear you asking, if a professional 5.1 monitoring system is no more than a toy, why is it called a "professional" monitoring system? It's partly marketing but not entirely, one of these professional 5.1 monitoring systems might be well suited to producing professional mixes for TV broadcast or DVD. They are also used by professionals in the film industry, in sound editing suites for example but they are NEVER used in theatrical mix rooms (dub stages). Accepting the fact that consumer and "professional" 5.1 monitoring systems are so completely different to theatrical sound systems, to mix a film requires an actual cinema sound system, ultimately there's no getting around that fact and believe me, people have been trying for years. You also can't stick a theatrical sound system in your basement or bedroom, despite the fact it wouldn't physically fit and would cost well over $100k, you'd only be able to enjoy the sound in such a small room for a second or so before your ear drums exploded and your liquefied brains ran out of your nose. You wouldn't have to worry about the mess though, the sheer physical power of the sound waves the system could produce would probably reduce your house to a pile of rubble anyway!
G
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