| There has been a long evolution in commercial movie | | | | apparently threw up their hands and designed and |
| theater sound. During the first two and a half decades | | | | arranged the surround speakers to: |
| of movie theater presentations, a piano, organ, | | | | 1. Really lag in time, (so the surround sound wouldn't |
| orchestra, sound effects man, or actors reading the | | | | arrive BEFORE the sound from the main speakers, no |
| dialog comprised the sound of movies. Electronic | | | | matter where you sat, and) |
| sound appeared in 1926 with the coming of the | | | | 2. Arranged for those speakers to smear their sound |
| "talkies." Theaters were wired for sound, and a big | | | | all over the back of the theater to mask the problems |
| speaker perhaps set behind the center of the screen | | | | caused by the great variety of audience/surround |
| did it all. This was the monophonic sound era. Then | | | | speaker time and distance relationships. |
| stereo sound arrived in the 1940's with left and right | | | | Now, along comes home theater. |
| channels. Additional sound channels were added in the | | | | Most home theater users don't fill the room with |
| 1950's. (Somewhere in there, a center channel was | | | | audiences, but the philosophy of earlier commercial |
| added to anchor the dialog to the center of the | | | | theater design is still being applied. You will observe |
| screen.) Finally surround sound came on the scene in | | | | how some home theater rear surround speakers are |
| the 1980's in various versions adapted to the acoustic | | | | designed to project sound in multiple directions and |
| challenges of the commercial movie theater. (The | | | | how the set up manuals will often direct that the |
| advent of DVD's brought affordable surround sound to | | | | speakers be placed to project their sound away from |
| our home theaters.) | | | | the main viewing location. |
| Home theater sound can follow any of these | | | | Here's the thing - if you want to reproduce the movie |
| commercial movie theater approaches, or it can move | | | | theater listening experience, use the surround speakers |
| beyond to new levels of sonic realism and effects. | | | | which try to spread sound all over and position those |
| One important difference between movie theaters and | | | | speakers to aid that goal. |
| home theaters is that movie theaters must present | | | | But, if you want to enjoy the more accurate sound |
| acceptable sound to a (hopefully) large group of | | | | source positioning (the sound appears to come from |
| people sitting at every location of a large room. In | | | | some exact location behind you, to your left, right, or |
| contrast, a home theater usually serves a much | | | | even overhead!) made possible by Dolby Digital or |
| smaller group of people sitting in a much more limited | | | | DTS, a different approach should be used. |
| part of the home theater space. | | | | In this approach (labeled "Holosonic Sound" by Gary |
| The limited size of the usual listening/viewing location in | | | | Reber and the gang at Widescreen Review magazine |
| a home theater can work to the advantage of home | | | | [ the rear speakers are placed behind the viewers at |
| theater owners due to the nature of sound | | | | about the same distance from the main listening |
| reproduction. | | | | position as the front speakers. They are usually |
| To understand how sound reproduction bears on this | | | | somewhat further apart than the front speakers. |
| discussion, let's start by considering stereo sound. | | | | These surround speakers should be: |
| In stereo systems, if a listener is closer to the left | | | | 1. Well matched to the sound quality (timbre) of the |
| speaker, all the sound apparently comes from the left | | | | front and center speakers. |
| speaker. If you have a stereo, turn it on and try this: sit | | | | 2. Direct radiating, and pointed at the prime listening |
| in a location equidistant from the two speakers and | | | | position. |
| listen to a good stereo recording with your eyes | | | | 3. Capable of handling at least one-third to one-half the |
| closed. Note the spread of locations the sound | | | | power that the front speakers can handle. |
| appears to come from. Now move a few feet to the | | | | 4. Located at a height at or slightly above the height of |
| left of and then to the right of center and notice how | | | | the ears of the audience. |
| the sound which was spread across from left to right | | | | (To prevent sound from the rear speakers from being |
| collapses into "all left" or "all right". This failure of the | | | | blocked by seatbacks, they might have to go a bit |
| stereo illusion is unavoidable when you use just two | | | | higher. The viewer's ears must be able to directly "see" |
| speakers. This means there's always a "sweet spot" | | | | the surrounds.) |
| (where the stereo effect works best) located on a line | | | | Home theater owners whose seats are right back |
| centered between the two speakers in a stereo | | | | against the wall will have to cope by placing the |
| system. | | | | surrounds on the back wall facing the seating, but |
| By the way, purchasing more expensive speakers | | | | spaced well away from the viewers (same distance |
| cannot overcome this effect, as the failure of the | | | | from the viewers as the distance from the front |
| stereo effect ONLY has to do with both the | | | | speakers to the viewers, if possible) to minimize the |
| differences in loudness between the two speakers | | | | collapse of the rear stereo effect if an audience |
| (due to being closer to one than to the other) and the | | | | member is not sitting exactly between the two rear |
| difference in the time when the sound arrives at your | | | | surround speakers. |
| ears from each of the two speakers. | | | | Movie makers today are releasing films on DVD with |
| The center speaker in movie or home theaters is an | | | | sound that is designed so that home theaters arranged |
| attempt to override this problem by placing a speaker | | | | to produce accurate stereo sound from good rear |
| in the middle of the screen for dialogue and other | | | | surround speakers will really give you the feeling the |
| sounds which the film maker wants to make sure | | | | you are inside the action, with actors sometimes |
| comes from the center of the screen, no matter | | | | speaking behind you, and sounds moving right out of |
| where you sit in the theater. The center channel | | | | the screen over your head. |
| solves the problem of stabilizing the dialogue but alas, | | | | How do you reliably adjust and test your home theater |
| any stereo sound being provided by the front left and | | | | for the kind of performance we're talking about here? |
| front right speakers will still seem to collapse to one | | | | Easy! Order the AVIA disk from Ovation Software's |
| side or the other if a person sits well to the left side or | | | | website. ( |
| the right side of the theater. | | | | Study the materials presented on the AVIA DVD, and |
| So, now let's consider the surround speakers. In movie | | | | then follow the instructions on the disk, or hire a pro to |
| theaters, the sound system designers are really stuck | | | | do the job after watching the DVD has helped you to |
| in a dilemma. Some audience members are often | | | | understand the outline of what has to be done. The |
| sitting right under or right next to one of the surround | | | | audio portions of this disk will assist you mightily in |
| speakers, which means there's no hope of the person | | | | tuning up your system if you do it yourself. It contains |
| hearing the other surround speakers' output at the | | | | "circulating" audio test signals that circle around the |
| correct volume and at the right time to get any sort of | | | | room and if you set up your theater for accurate |
| stereo effect from the surround speakers. This is | | | | surround sound, that test will show you how well |
| probably why the older Dolby Pro-Logic system rear | | | | surround sound can work in your home theater. |
| surround was only monophonic. | | | | It can be very satisfying to have better surround sound |
| Instead, sound system designers for movie theaters | | | | than the commercial movie theaters. |