How many speakers do I need?
How many speakers do I need for my home theater?
Most home theaters are in the 5.1 format and consist of six speakers. Those speakers are a center speaker, one each of a left and right speaker, one each for left and right rear surround speakers and a sub-woofer. So you will need five main speakers and a powered sub-woofer which accounts for the ".1" of the 5.1 format designation.

The five main speakers can be identical however many better speaker systems will have a better/bigger speaker for the center channel because it handles the main portion of the dialog in a movie. Some systems also have larger speakers for the left and right channels to help balance the front sound-field.

Your powered sub-woofer handles the bass/low-frequency effects such as explosions and other rumble type effects. Your sub-woofer should be at least twice as powerful as your other speakers due to the fact that low frequency sound waves take more power to reproduce with clarity and punch.

A 6.1 systems adds a center rear surround speaker to help fill in the gap in the rear between the right and left rear surround speakers. If you want a 6.1 system you will need another speaker which will bring your total speaker count to seven.

Likewise a 7.1 system will have eight speakers with the addition of yet another rear surround channel speaker. Actually the additional speakers are used as more of a right and left "side-fill". Those channels are decoded by the receiver from the original 5.1 mix. Frankly such systems are usually unnecessary unless you have a really large room.

In conclusion -- the basic answer to "how many speakers will I need" is six. However you have a choice of six, seven or eight speaker configurations if your particular situation warrants the addition of more speakers.