Surround Sound or Stereo?

Often I’ll meet clients who say that they want surround sound. After probing further I realize that they don’t know what surround sound is. Fair enough. Surround sound is simply what’s been sold to them. They get bombarded with advertising touting surround sound, and it gets promoted very well in the movie theaters right before the picture starts. You may have seen this. THX, a company involved in establishing surround sound standards, runs strikingly bold and clear sound clips coming from all around the theater, or maybe just to the side or just behind you. There is an organ like sound that ramps up in volume and contains a low rumble, there is the sound of glass breaking, and the one I find most impressive, the baby crying. The first time I heard it I thought that there was a real baby in the movie theater. Anyway, it’s only natural that clients assume surround sound is what they’ll be buying. Stereo is their other option, and so I explain that as well.

Surround sound is designed to provide a sound-field in front of you, to your sides, and behind you. It can also recreate a sound above you. (This is used to creepy effect in the movie, The Others, where footsteps can be heard as if coming from the room above you.) Most all modern movie soundtracks are recorded for surround sound. Very little music is recorded in surround sound.

Typically, a surround sound system uses five speakers and a subwoofer, and when the room is long, seven speakers and a subwoofer. Three speakers are installed along the wall with the TV–this wall is referred to as the front wall. These include a center speaker, which is above or below the screen, and then a speaker to the left (i.e. the viewer’s left) and a speaker to the right of the screen. One or two pair of speakers are installed along the side and/or rear walls. The goal of surrounding you with sound in all directions is to immerse you in the sonic environment that is suggested by what you’re seeing on the screen. That is, if a character shoots an arrow into the camera, the whooshing sound of the arrow traveling towards the camera and then continuing behind the camera will be handled by the surround system. To the listener, it sounds like the arrow travels from the front of the room to the rear of the room. Such blatant use of surround sound happens frequently in action movies, while in dramas its application is subtle. For a scene of a couple strolling through a city park, for instance, the surround system might play traffic and bird noises in the surround speakers (i.e. side wall and rear wall speakers), again to immerse you in the sonic environment that is suggested by the film’s scene. If explosions (i.e. action movie) or bird chirps (i.e. drama) happening behind you sounds fun, surround sound may be for you. Most avid action movie fans get surround sound.

The alternative to surround sound is stereo sound. Stereo systems require a front left and front right speaker. Stereo creates a sound-field that, more or less, is shaped like a performance stage that is situated in front of you–as if you’re sitting in a stage theater. (Surround sound recreates this same performance stage, but it adds the ability to place sounds to the sides and behind the listener.) The front edge of the stereo soundstage corresponds to an imaginary line drawn between the fronts of your two speakers. The left side of the stage corresponds to an imaginary line drawn from the left side of your left speaker straight back through your front wall. The right side of the imaginary stage corresponds to an imaginary line drawn from the right side of your right speaker straight back through your front wall.

For a listener sitting equidistant between the left and right speakers, and at least as far away from the speakers as the speakers are from each other, a three-dimensional sound-field is reproduced. That is, sounds are recreated pretty much anywhere within the boundaries of the imaginary stage. The voice of an actress standing in the center of the screen will sound as if it’s coming from right between your speakers. If she should step ten feet straight back and three feet to the left then her voice will sound like it’s ten feet behind your speakers—yes, even if your front wall is only 3 feet behind the speakers—and three feet left of center.

Now, for listeners not seated equidistant from the left and right speakers, sounds still seem to come from this imaginary stage area, but the sounds’ locations are skewed towards whichever speaker is closer. These locations are not the ones the recording engineer intended. Think again about the actor speaking from center-stage. The listener who is seated equidistant between the speakers will hear that voice coming from center stage—as intended. Listeners seated closer to the right speaker will hear that actors voice coming from somewhere to right of where the actor is standing. Truth be told, only audiophiles care about this sort of spatial accuracy.

Most people could have their speakers on the left wall and their TV in front of them and it wouldn’t detract from their enjoyment. At drive-in movie theaters the speaker is hung on the car window and the screen is a couple of hundred feet in front of the windshield. It sounds weird for about the first minute—if that—and then the viewer’s brain puts the sound where the visual is. Our brains are good that way.

By the way, if you’re one of the few who do care about spatial location then you’ll want to be sure and have a listening spot that is precisely located—even for a surround sound system. Ask your system designer to find that spot for you if you’re not sure. Interestingly, when in this spot, a stereo system will place surround effects (e.g. as in action movies) behind you.

OK, so there you have an explanation of surround sound and stereo sound. These systems are all about manipulating where we perceive the sound coming from. These systems have nothing to do with the inherent realism of the sound. (i.e. whether a violin sounds like a violin or a voice like a voice). A system’s ability to properly place sound is not important to most people in the market for home theater. Here are some facts that they do find interesting.

Given a particular budget, the stereo system will be higher quality than the surround sound system.* We’re talking about bass that is deeper and more articulate, the ability for the system to sound clear at low and high volumes, and the ability of the system to recreate the musical dynamics faithfully (i.e. let the sound rise and fall in volume in proper proportion, rather than in a compressed fashion). That the stereo should sound better than the comparably priced surround system is opposite what many consumers think.

For one, it’s assumed that surround sound is inherently superior to stereo sound. This assumption is natural, because surround sound has more speakers and more is assumed to be better. And, in fairness, more is better, in theory. But, remember the condition about the fixed budget. If you have $500 to spend on stereo speakers, you are spending $250 per speaker. If you have $500 to spend on surround speakers, you have $100 to spend on each speaker. Which speaker do you think stands to be better, the one that cost $250 or the one that cost $100?

Now, one might argue that surrounding the listener with five $100 speakers makes up for the fact that they are inferior to the two $250 speakers, which are only in front of the listener. One might argue that while the $100 speaker doesn’t recreate as natural sounding a human voice as the $250 speaker, the fact that there is a rear speaker at all, one that can create the illusion of the voice coming from behind you as the director of that haunted house movie wanted, makes the five $100 speaker system better than the two $250 speaker system. That’s a valid point of view, at least for such movies (e.g. thrillers, action movies).

For music playback, not so much. Nearly all music is recorded for playback in stereo (i.e. with a front left and a front right speaker only). For dramas, not so much either, as the surround speakers (i.e. the ones on our side and rear walls) are going to be playing ambient noises only. Unless you value those ambient noises more than the absolute true-to-life fidelity of the sound in general, you’d want the two $250 speakers over the five $100 speakers.

This particular equipment difference, that of two speakers for a stereo system versus five for a surround system, isn’t the only difference. Your dollar is also getting spread thinner in the surround sound system because you have to buy amplification for five speakers instead of amplification for two speakers. Again, given the arbitrary amount of $500 for amplification—amplification is often addressed when one buys the audio/video receiver, for instance—which amplifier do you think will be higher quality, the amplifier that has to power five speakers or the one that has to power two speakers? In the case of the surround system, we have $100 of amplification for each speaker. In the case of the stereo system we have $250 of amplification for each speaker. Chances are, that stereo amplifier is going to sound better than that surround sound amplifier.

Oh yes, the surround sound system requires that your budget be spread thinner still, as it requires a surround sound decoder—again, this is being paid for when you buy the audio/video receiver. There is no such expense in the stereo system. In the stereo system these dollars are therefore available for better speakers, amplification, DVD player, etc.

Also, the labor cost of installing a surround sound speaker system is at least 2.5x greater than it is for installing a stereo system. Five speakers are 2.5x greater in number than two speakers. Also, you have to pay an installer to calibrate a surround sound decoder. There is no surround sound decoder in a stereo system.

After I explain the pros and cons of stereo and surround, I’d say about one-half of the people who come to me thinking that they’re going to be buying a surround sound system wind up buying a stereo. Either way, the goal is to make sure that you’re spending your own dollars to your best advantage. An audio/video company with experienced system designers can help you do this.

*One area where stereo’s superiority is called into question is in the area of dialog intelligibility. While I have personally have not had a problem in this area, some believe that when a 5.1 sound track (i.e. most modern movies on DVD) is played back through stereo speakers, dialog intelligibility suffers as compared to when a center speaker is used. For those so concerned, but who still want quality sound over surround sound, a solution is to invest in the surround sound receiver, but buy only a left, center, and right speaker (i.e. no rear speakers).

I suspect that this issue is more likely to arise when the soundtrack contains sound happening simulaneously with the dialog. Action movies fit this bill, which could be why I don’t have this problem. If you’re an action movie fan, you probably want surround sound anyway.

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