16" Parabolic Microphone Dish for DJI Mic Mini, Tested at +14 dB

A true parabolic dish, 16 inches (406 mm) across, built to record elk bugles in Great Smoky Mountains National Park. Focal length is 4.0 in (f/D 0.25), so the focus sits right at the rim plane and the mic is tucked inside the dish, out of the wind. The mic is a DJI Mic Mini transmitter on a slide bar, with a scale marked every quarter inch.

Does it work? I measured it. From the far edge of a clearing, the dish recorded my voice about 14 dB louder than the bare mic at 2 kHz, and 14 to 19 dB louder at 4 kHz. With the bare mic, my voice sat about 5 dB under the background hiss. With the dish, it sat about 9 dB over it. Every bugle in the film below came through this dish.

Spectrograms, charts and audio clips: I 3D Printed a Sound Dish. Then I Measured It.

The film it was built for: Cataloochee Valley elk, on YouTube

Print list

• tabtest.stl ×1. Print this first (about 10 min). Tabs are 1.6 / 2.0 / 2.4 / 2.8 / 3.2 mm. Find the one the Mic Mini clip grips snugly.

• quarterA.stl ×1. The quarter with the slide-bar housing.

• quarterB.stl ×3. Plain quarters.

• handle.stl ×1. Clamp ring and grip, with a 1/4"-20 tripod socket.

• bar_tabX.X.stl ×1. Slide bar and mic arm. Print the one that matches your tab test.

• elk_dish.scad. OpenSCAD source, every parameter at the top. Change the diameter, focal length or mic size for your own rig.

Every part fits a 220 mm bed and is already oriented for printing. The quarters stand on their seam flange; in that orientation every surface is within 45° of vertical, so no supports. Each quarter is a tall, thin print, a little over 8 in high. Use the brim.

Settings (PLA)

• About 850 g total, one 1 kg spool. 0.2 mm layers.

• Quarters: 6 walls (the 2.4 mm shell prints solid), 15% infill, 8 mm brim, glue stick, no supports.

• Handle: 4 walls, 25% infill. Bar: 4 walls, 40% infill.

• Roughly 4 to 5 hours per quarter, 20 to 24 hours for everything. Check your slicer.

Hardware (#10-24 except the tripod nut)

• 16× #10-24 × 3/4" machine screws, 16 hex nuts, 32 flat washers (seam flanges)

• 1× #10-24 × 1-1/4" machine screw, 1 wing nut, 2 washers (handle clamp)

• 1× #10-24 × 1/2" thumb screw and 1 hex nut (slide-bar lock)

• 1× 1/4"-20 hex nut (tripod socket, drops in from the top of the grip; dab of CA glue)

Assembly

1. Bolt the four quarters together at the seam flanges. Snug the bolts, line up the inner surface flush across every seam, then tighten. Don't crank on PLA; the washers spread the load.

2. Slide the handle ring over the round hub on the back. Its notches key onto the flange stubs in any of 4 positions. Point the grip down and away from the slide housing, then tighten the wing nut.

3. Press the #10 nut into the trap at the back of the slide housing and thread in the thumb screw.

4. Feed the bar through the housing from the front, arm pointing toward the dish center.

5. Clip the Mic Mini onto the tab with its mic grille facing the dish center. Slide it until its bottom touches the arm. Windscreen on.

Where the mic goes

The number at the back face of the slide housing is the approximate distance from the dish vertex to the mic grille, in inches. The design focus is 4.0. In my test, 3 to 4 in did best at 4 kHz, and I mark 3.5. A printed dish is never a perfect paraboloid, so test yours: record a few seconds at each setting from one fixed spot and keep the sharpest.

What to expect

A dish only grabs sound waves shorter than it is wide, so the gain starts around 850 Hz. Birdsong, voices and the whistle of an elk bugle get a big lift. Low growls and rumble get none. The dish also catches a little extra low-end wind noise, which a high-pass filter cleans up.

Caution: PLA softens around 55 to 60 °C. Don't leave the dish in a hot car.