Main Speakers... It's All About Symmetry
Having your main speakers setup so that they're equidistant from your center listening position improves the imaging of the sound stage tremendously. This placement allows the speakers to work together enveloping you in a 3-dimensional presentation of sound.

To figure out where your speakers should be placed, mark on the floor or drawing of your room where you center seating position is. This should line up with the center of your TV. From the center of your TV you'll want the speakers to be equidistant from center. To find out how far your speakers should be away from center to produce the optimum sound you can use the following equation:

1. Measure the number of feet from your centered seated position to the center point of the TV.
   
   
2. 2/3 of that number is the distance your speakers should be apart. The center of this measurement should originate from the center of the TV.
   

Example: If you're head is 9 feet away from the center point of the speakers, then your speakers should be placed 6 feet away from each other. These rules are merely a guideline, but are a really good place to start.

The Right Height
To obtain the best sound, use speaker stands to get your main speaker's tweeter at your seated ear level position. This measurement doesn't need to be dead on, but the closer you get the better.

To measure, simply have someone measure the distance from the ground to the level of your ears while you sit. You can also mark your chair with tape or estimate how many inches above the back of your chair that your ear level is.

After that, with your speaker on the floor, measure the distance from the floor to the center of the tweeter. Subtract the speaker measurement from the ear position measurement and that's the size of the stands you need.

While you most likely won't get an exact match the idea is to get as close as possible. If you need to decide between a stand the puts the tweeter slightly lower versus slightly higher, opt for the lower configuration. Speakers sound best with their tweeters at or below ear level. Besides, you'll also be able to save money buying smaller stands.

Having your main speakers face forward and not angled or "toed" in toward the listener really opens up the wideness of the soundstage. "Toeing" in the speakers can improve the centering of the soundstage, but can result in a loss of spaciousness. If you need to place your speakers farther apart than this guide suggests, you may need to toe them in a little so that a soundstage can be made. Try it both ways to see which way you prefer.

Center Speaker Top or Bottom
Center speakers require almost no thought to setup. Simply place them on top of your TV and viola, voices are now anchored to the screen. You may get better sound if your cabinet allows for placement of your center channel below the screen. In most cases this option is not available, but if it is give it a try.

Surround Speakers... Any Which Way
There are many different positions in which you can place surround speakers to produce great surround sound, but there are a couple of techniques that produce the best enveloping surround.

Dipoles
For movies, which is what home theater is all about, some of the best surround sound can be achieved by using dipole speakers directly to the side of your listening position.

Dipole speakers have drivers on both the front and back of the speaker, and are usually mounted to the side walls. Sound is radiated both forward and backward producing a sound field that blends in with the front speakers while using the reflection of the rear walls to produce an ambient sound field behind you. None of the drivers face your listening position so you can't hear the speaker's location.

This huge envelop of sound comes at the cost of precision, but offers a very spacious experience. If you desire precise effects from your surround sound system then direct radiating surrounds may be best for you. It all comes down to your personal preference.

Direct radiating
Direct Radiating surround speakers have drivers only on the front of the speaker. The surround sound produced by using these types of speakers is very precise and localized.

The advantage is that the two speakers (when set up symmetrically) can produce a sound stage similar to that of your main speakers. This makes is possible to hear items come from directly behind you while no speaker is there at all.

The disadvantage is that this setup draws a lot of attention to the speakers causing possible distraction from the movie.

With direct surrounds you'll want the surround speakers facing your seating position, but you also want their sound to blend in with the mains too. The best setup with direct surrounds is to follow similar guidelines to setting up your main speakers, but angle or toe them in so they face the center seated position.

You'll want them to be as symmetrical as possible with the tweeter at ear height. The big difference in setting up direct surrounds versus the main speakers is that you'll want the surrounds to always face your center listening position.

Direct surrounds will sound better when they're as far away as possible from your seating position. This allows the sound from the speakers to play with the room more, thus opening up the sound field.

Surround Summary
The guides above are a good place to start, but they're just guides. It's a good idea to experiment with the surround speaker's location until you find one that you like best.

All rooms aren't created equal which makes the surround speaker one of the most difficult to setup. If your room doesn't allow you to place your surrounds symmetrically you can make up it by calibrating the speakers to make the sound balanced. See Calibration for more info on this.

The Subwoofer
Most people think this is the easiest speaker to place. "Just plop it in a corner and your done, right?" Wrong. Depending on where you sit, and the walls in your room, the subwoofer's bass response can vary dramatically when moved just a couple feet.

Walls reinforce the bass, but if a sub is placed too close, the sound will be boomy and muddy. Pulling the sub away from the walls produces more accurate and tighter bass, but you will loose some of the thunderous qualities many people prefer. There is a happy medium, and it's easy enough to move the sub around until it produces the sound you like best.

Sound nulls are created when two sound waves converge at the same point in the listening room. Where they converge they cancel each other out, resulting in zero bass in that part of the room. It's near impossible to have a home theater without null areas, but the trick is to not have a null area in any of the listening positions. The only way to change a null area is to move the sub (or the angle it faces) so that the null areas are in a different spot in the room.

The best position for a sub is directly in the center of the main speakers. A TV usually takes up that location so that rules out that idea for most home theaters. Off to either side of the main speakers is usually where subs end up. This isn't always the best location as it tends to be too close to the corners of the room.

It's best to try every location you can think off. At the side walls facing straight forward, behind the couch, or next to an end table are other possible solutions. Each location will produce different qualities of bass. The best position will produce thunderous bass in all sitting locations. It can take a little time, but you should be able to find your room's balance.

The Walls
More often than not, your walls will dictate more where you place your speakers versus proper measurement. Walls effect the sound of your speakers dramatically. Too close to a wall and the open sound-stage your speakers should produce becomes flat with boomy and muddy bass. Too far from the wall and the bass seems almost lacking.

Mains
Your main speakers should be placed at least 1ft forward from the wall behind them and a greater distance away from the side walls. You never want the distance from the side walls to be the same as the distance from wall behind your speakers as it can adversely affect the sound.

Center
The center speaker really has no choice on how far it can get away from the wall since it rests on the TV. In fact, it's the TV that's your center speaker's wall. The TV's reflective qualities can adversely affect the center channel. The best way to reduce the TV's affect is to have the front of the center speaker align with the front of the TV. One better than that is to have the center overhang the TV by an inch. That should greatly reduce TV's affect.

A word of caution: most center speakers are front heavy and this placement can increase the chance of the speaker falling forward. If your speaker tips forward with this placement you should move the speaker back or find a way to brace it to your TV.

Surrounds
Dipole surrounds are placed on the side walls and actually use the highly reflective nature of the walls to create an ambient sound field

Direct surrounds follow similar guidelines to the main speakers. The only problem is most rooms don't allow for symmetrical placement of surround speakers. As with the main speakers, direct surrounds sound best when pulled away from the walls about 1 ft with the distance to the side walls being a different measurement. Try to avoid wall mounting the direct surrounds as this can ruin the spaciousness of the sound.

Subwoofer
Subs follow the mains in that the measurement from the back wall shouldn't be the same as the measurement from the side wall. Subs use the walls to produce bass and, the closer to a wall the sub is, the more bass it will provide. The subs "line of sight" can affect how low the sub can go. To produce the lowest bass frequencies a sub needs to have at least 20 ft of open space in front of it. Usually this isn't possible, but if it is, give it try an see if you notice the quaking difference.

Summary
Getting your speakers placed in the right location can take some time, but it should be interesting to hear how the different locations affect the sound. Overall have fun. Start with the basic guides outlined above, and then work form there.