- What are the differences between typical stereo speakers and home theater speakers?

Speakers perform best when the listener's head is directly in front of the speaker and at the same height as the drivers. The sound response where the driver is pointing directly at the listener is called the on-axis response. When you move off-axis (to either side or a different height), the speaker will not sound as loud.

Normally, stereo speakers have a better off-axis response than home theater speakers. The sound that the listener hears is a mixture of the left and right channels, combined with the reflections of the both channels off the walls, floor, and ceiling. Stereo speakers sound best when the listening area is centered and in front of the two speakers, but they also sound good from either side of the room. For a well recorded soundtrack, both the left and right signals might contain the same music, but they will not be at the same volume levels. Different instruments will be at different levels in the different speakers. If you are directly in front of one of the speakers, you should still be able to hear some parts of the music coming from the other speaker.

The front speakers in a home theater system are designed to have just the opposite effect. They have a very short vertical off-axis response that limits the dispersion of the sound in the room. This is done to prevent the reflection of the sound off the floor and the ceiling. The reason for this is simple. In a home theater system, there are 2 rear speakers to provide the sound from the back. The reflection from the front speakers will only interfere with the job of rear speakers. When mixing the sound for a movie, the editors want you to feel like you are in the movie. If the actors are in a large room, then the echoes should appear to be deeper and take longer to arrive back at the listener. This is impossible if you can hear the reflection of your front speakers off the back wall of your living room. Ideally, the only reflection you should hear is the false reflection provided by your rear speakers.

- What about the rear speakers?

The rear speakers in a home theater system have a greater diffusion than you would get with stereo speakers. Sometimes, rear speakers have drivers firing in multiple directions. This causes a lot of reflection against the walls and makes the rear echoes sound like they are coming from a wide area.