Design of folded (reentrant) horn typically used in public address systems.
You can read more horn theory at wikipedia (https://en.wikipedia.org/wiki/Horn_loudspeaker)
Reentrant horn basically amplifies sound at cost of cutting off low frequencies.
See demonstration here:
Horn was designed in Autodesk Inventor and many properties were parametric. You can modify cut-off frequency, horn length and width, speaker radius, etc. See image attached and video:
Horn shape is hypberbolic.
Source Inventor file is included.
The published horn design was parameterized for this type of loudspeaker:
"1.5" inch 4Ohm 4Ω 3W Full Range Audio Speaker Stereo Woofer Loudspeaker"
Note: base part includes supporting cylinder (brown part at the picture) for better print. It can be disabled in Inventor if you don't want to use it.
You can also check my Hyberbolic Horn design: https://www.thingiverse.com/thing:1915305