Folded (reentrant) Horn, parametric

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:
https://youtu.be/as_s8Ir7qb0

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:
https://youtu.be/0CKh6awGGPM

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"
http://www.ebay.com/itm/331269348255?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

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.