The width of the speakers will determine where you need to drill the holes for your speaker horns.
I found this speaker system at a dollar store, the speakers are just under two inches apart.
I wanted to play sounds from the first era of recordings. I downloaded a bunch of recordings from the cylinder preservation project, http://cylinders.library.ucsb.edu/index.php
Songs from the right era add to the effect I wanted.
Your software and audio player will vary, and you'll know how to download music to your player.