A Loud-speaker that has a sufficent rangde from 10
Hz to about 500 Hz. They can range in size from
4" to 34". They can range in price from $100 to over $2000. They can be used as part of a home theater
system(usually the ".1" in the 5.1 or 9.1)
or they can be used for sound quality or SPL(Sound Pressure Level) Competitions. If
properly amplified with enough power, they can reach 177.0
Db!