Passive phone amplifier
thingiverse
I designed a phone holder specifically for my LG V20, which has a Spigen case on it. It should work with most phones that have bottom-facing speakers. Link to the blog post about how this was modeled in Fusion 360: http://3dprinting.illustratingmath.com/2018/10/11/phone-amplifier/
Download Model from thingiverse
With this file you will be able to print Passive phone amplifier with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on Passive phone amplifier.