70/100V speakers are used in professional sound systems where large areas need to be covered with multiple audio playback points. These systems allow for connecting multiple speakers to a single amplifier over long distances with minimal signal loss. They are ideal for applications such as public announcements, background music, or voice evacuation systems, commonly used in schools, commercial buildings, hotels, and industrial spaces. 70V systems are more common in the USA, while 100V systems are prevalent in Europe.