Making flat panel speakers from a cheap piece of foam board? Crazy idea? Yes, but it works.
Does it work?
Just take a look at the video, where they describe all the processes of making it. It is incredible how foam boards where each cost around $5, and the audio exciters $25 for each can sound.
To be honest, the sound quality you can get out of a set of foam speakers they have built in a few minutes is amazing.