Passive Amplifier (Megaphone) for the Galaxy S4 Armored PEPK case

I use my phone for music at work and using it at full volume drains the battery quickly, so I designed this megaphone dock so I can play at half volume to keep my music loud and the battery full. There is a hole beneath to allow a charging cable to snake up from the rear and into the phone.
The middle section is used mainly for larger cables that don't have a flexible cable while you want to keep it charged while playing music.
On the bottom of the stand, there are two spots for magnets to b