2.1,5.1,7.1...What do these numbers mean?(in hometheaters)

Ever wondered what these numbers mean in 2.0/2.1/5.1/7.1 etc. (in hometheatres)

In general these number can be expressed like  A.B  . Where A is the number of satellite speakers (the small speakers)and B is the number of Subwoofer(s).Small speakers(known as surround speakers) plays medium frequency sounds(dialouges) and high frequency sounds(sounds like ssss).Subwoofer plays low frequency sounds(bass).

Given below is the explanation of various speaker configs. with pictures.

• 2.0 means it has two speakers,one each on left&right side.But no subwoofer.

• 2.1 means same as 2.0 and a subwoofer.

• 5.1 means same as 2.1 and another 2 speakers (one on your back left&one on your back right) and one center speaker and a subwoofer.

• 7.1 means same as 5.1 and 2 additional speakers(one on left side&one on right side) 

           and a subwoofer.

In all these,Surround speakers give sound from various directions.The center speaker in 5.1&7.1 are used to play dialouges in movies and games.Ofcourse there are some more speaker configurations exist like 2.2,4.1,5.2,8.1,11.1,12.1 etc.They have more surround speakers and or subwoofers.7.1 to 12.1 are mainly used in movie theaters.We have explained only more used configurations.