IP stands for Ingress Protection which is an international measure for the effectiveness of a product against foreign bodies. Following IP, two digits are given (like IP66, IP25 and so on). The first digit indicates protection against intrusion and the second digit indicates protection against moisture. If the digit is replaced by X (like IP5X or IPX0), it indicates no particular protection. If the first digit is X, it means there is no intrusion protection and X as a second digit indicates no protection against moisture. With IP rating denoted in the product’s description, you can check what your speaker is capable of withstanding.