If you are on decent terms with him, talk to him. If the loud music bothers you, it likely bothers some of the other neighbors, talk to them as well. Maybe one of them can get the point across. If he's a little 'slow', you need to be consistent and persistent, each time the problem comes up. Your disruptor beam idea won't likely be all that directional, it'll effect other neighbors as well. Probably get a few nasty shocks off it anyway, messing around with high voltage... Try peer-pressure, power in numbers. You and a few neighbors confronting him throughout the following day, about his late night behavior, will change it. Nobody likes confrontation, or being singled out in a community. Whatever his reasoning for playing his music loud late at night, won't justify the consequences the following day. When it's just you complaining, he'll figure you're just having a bad day, and taking it out on him. That logic doesn't work, if other neighbors raise the same issue later in the day. The more people involved, the stronger the reinforcement of the message.
You can mess with the stereo, but wouldn't he just buy a new one, figuring it defective?