Exponential Horn

For an outdoor recording project I wanted a small offset exponential horn that transitioned from round to square. The round end connects to a 9.7mm OD round electret mic (PUI Audio AOM-5024L-HD-R) and the other end matches a square opening in an enclosure.

You may notice it is not axially symmetric: the small round end is offset from the centerline, so I can mount it horizontal but with the mic element towards the top. That way any rain that might come in the open end would tend to run down