What kind of machine should be used for the elderly to dance outdoors? The sound should be able to pass, can read the best U disk

Suggest that you go on Taobao search "amplifier", (do not buy "radio"), we have a lot of people bought the first and Xiaxin's, you can read the U disk and memory card, battery capacity, a charge can be put on the 7-8 hours, the volume of the largest to 400 meters, the better there is a song selection function. 400 meters, the good ones also have the function of selecting songs. Generally only a few dozen dollars.