I saw a wooden design of a phone amplifier in a book called “Build stuff with wood”. I decided to make a 3D printable version. If you don't use the profiles, I recommend you manually add the supports only at the beginning and the end of the tunnel. No need to put support inside, your printer can bridge it. 

Phone requirements:

• Designed for phones with speaker on the right
• Maximum phone with of 80mm

Don't expect too much off this, the amplification level is not incredible, but it makes the music a little louder and clearer. It can also serve as an oversize phone holder!