Step 1: The finished speaker box
Although this was made from card you could just as well use polypropylene as a harder wearing material, you can often buy stationary folders made from polypropylene that you can recycle.
Step 2: The Net for the crash lock box
Step 3: Cut out and speaker fitted
Step 4: Last step
Even a simple test shows an improvement to the sound from a very small speaker. A bigger speaker will sound better.