I modified an older design to fit the iPhone 6 (also added model for iPhone 6 Plus plus). This is a passive amp/speaker/horn/stand for iphone 6 that I modified in Tinkercad (shared publicly there too). I find that it doubles the volume when playing music, although it is a little bit echo-ey (that’s the trade-off). The design is really similar to turn of the century phonographs!
I printer with PLA on a raft (on heated bed), came out pretty good, although the “gold” PLA I used is more brownish-yellow with some sparkles… I’d probably do ABS next time…