Your system would be pretty quiet if you did not have any speakers. There is are many things to be considered when evaluating a speaker. What I will try to do is to break down some of the terminology that goes along with identifying a speaker. First off for the people new to home theater, a home theater set up usually consists of a minimum of five speakers. They would be two front speakers, two surround speakers and a center channel. Unless you are using powered front speakers, I will cover them a bit later, you will most likely want to add a sub woofer.
Lets break down the setup . When you go to a theater you see speakers all around you. There are speakers to left and to the right of you there are speakers behind the screen and there are speakers in back of you. The goal of home theater is to try to duplicate the sound you hear at the theater at home. This is obviously done with fewer speakers. But if it is done right it can sound just as good if not better in your house.
All right lets talk speakers. I will start with left and right speakers. Those are important because they project the sound and voices that are to the left and right of the screen. The sound track is also played through these speakers. Many different kinds of speakers can be used for the left and right speakers. There are many different types of front speakers to choose from. Along with different hook up options for them. One type is called a book shelf speaker. These typically are small and light so that they can be wall mounted or put on a book shelf. As a rule there frequency response is not that extended. Let me explain what frequency response is. Human beings can generally hear from 20hz to 20,000hz. That is the range of sounds that we can discern. That range is equal to low bass through high treble. The lowest part of the spectrum is bass. This is generally 20hz to 200hz. Midrange is where most of the basic tones we hear are. This is usually from 200hz to between 500 and 1kh. Treble is between 1,000hrz up to 20,000 hz.
Another type of speaker is known as floor standing or tower speaker. These speakers can range in size from three and half feet to over six feet in height. Some of the can weigh close to 1,000 pounds each. These speakers usually have a combination of different drivers. A driver is what you call the individual part of the speaker. Some one might say this speaker has two 6 and half inch drivers. That means that it has two individual speakers that are both six and half inches big. One example of a floor standing speaker is the B&W N803 3 way speaker. This speaker has two 7 inch woofers one 6 inch midrange and one 1 inch metal dome tweeter. As you can see it can cover almost the entire spectrum. It is rated to go down to 35hz. This is very good but you are missing the very bottom of the bass spectrum. But none the less this is good extension for the driver complement that this speaker has. With in the floor standing catagory you have some speakers that have drivers on only one side of the speaker. These are called direct radiating There are also speakers that have drivers on both sides. This type of speaker is called a bi-polar speaker.
There are also speakers that are powered. For instance Definitive Technology, Paradigm, and Mirage all have speakers that include some sort of amplifier to power them. The advantage to this is that you may not need as much power from amplifier to power these types of speakers. The powered section is usually a woofer of sub woofer section. This can drastically increase the amount of bass coming from the speakers. In some cases because the sub woofers in the main speakers are so good, you don't need a separate sub woofer. There are obvious benefits to this. One is that it can save you space and time because you don't have to worry about placing your stand alone sub woofer. The second benefit is that you have two instead of one. Another advantage is that you do not have to worry about cross over settings or how the sub will integrate with your main speakers. Powered speakers almost always have the bass crossed over already so it should sound very smooth and natural.
Crossovers are important to understand. Basically
what a crossover does is let certain frequency's go to the speaker and
keeps certain frequency's away from the speaker. This might be a
good place to talk about sub woofers. A sub woofer is a speaker that
is designed for one reason. To play the lowest part of the audio
spectrum. Sub woofers almost always have their own built in crossover.
It usually contains what is called a high pass filter and a low pass filter.
Strictly speaking the high pass filter should keep the higher frequency's
out of your sub. And the low pass filter should keep the lower frequency's
out of your main and other speakers. This is important because if
you have a small speaker or a speaker that can not handle that much bass
you could ruin the speaker by sending it more bass then it can handle.
This intern might damage the speaker or make it sound poor. I say it will
sound poor because when a speaker attempts to put out more bass then it
is supposed to, especially at high volumes, you can hear the change.
It no longer sounds smooth. Now, getting back to the sub woofer they are
generally used to play from 80hz on down. A sub woofer can range
in size from 8 inches to 18 inches. If they are powered their amplifire
can be from 50 watts to over 2,000 watts.