Expandable horn sound box

The utility model relates to an expandable horn sound box comprising a partition, which is provided with a through hole and divides the speaker into two intercommunicated parts, wherein one part is an installation part in which a speaker is installed, the other part is a horn-shaped extension part, and an included angle formed between a tangent at the edge of the extension part and a central axis of the sound box is 45 degrees. According to the utility model, sound pressure is increased by arranging the partition to collect and contract the sound produced by the speaker; and sound field is increased, transmission distance is made greater, and acoustic fidelity is made better by amplifying the sound through the expansion part. The expandable horn sound box provided by the utility model is simple in structure and low in cost, and can be used widely in squares or other outdoor occasions, and thus the requirements of large-scale performances in a huge outdoor square is satisfied.