I know JBL charge 4 says its 30W but i can tell you that my speaker was quite a lot louder then it. Granted, it didnt have good bass but it was a lot louder. Maybe the speaker inside JBL charge 4 is 30W and amplifier is only feeding it 15W or something like that. Anyway i will have to do some testing and find some proper material. I cant seem to find the right plastic to make my own speaker cases, i only found pvc sheets in store and they are so expensive its crazy, not to mention that unlike this nice plastic, pvc will break often when cut with jihsaw.