Build a D.I.Y Brahma Ambisonic Microphone.

This is a step by step tutorial that shows the process of building a Brahma Ambisonic microphone. You start by modifying a Zoom H2n and converting it into an ambisonic microphone by following these simple steps. This tutorial was written and compiled by Sai, Dhanya, Sushmita, Aayush and Sudhanshu with the help of Umashankar Manthravadi.

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Introduction to Brahma Microphone

Brahma Microphone is an ambisonic microphone made by modifying the Zoom H2n microphone. The Zoom H2n is the successor of the H2 microphone. The Brahma microphone can be used as a portable ambisonic recording device. The capsules in the Zoom H2n are small and convenient to use but capture more noise. By introducing bigger (14 mm) capsules that capture less noise in a tetrahedral array to the Zoom H2n microphone, it can be modified as an ambisonic microphone.

List of Materials Required

1. Soldering iron

2. Soldering wire

3. Zoom H2n recorder

4. Tetrahedral Array - 3D printed (Download the .stl file here)

5. A lot of small screws (0.8 mm and 1.2 mm- mobile sized not sure about dimensions)

6. Small wire cutter (to cut wires)

7. Big wire cutter (to cut off plastics)

8. Two Star Screwdrivers (0.8 mm and 1.2 mm - used for mobiles)

9. Four Capsules (14 mm)

10. Multimeter (to check +ve and -ve terminal)

Step-by-Step Instructions

1. Open the battery cover from the back of the Zoom H2n microphone and remove the batteries if they are present.

2. Unscrew two tiny screws on the top two corners using the small star screwdriver. As a result, the Zoom label (plastic) comes off.

(Note: Be careful when unscrewing so as to not strip the heads of those tiny screws since we need them later to close the microphone. If stripped, find replacements.)

3. Unscrew four bigger screws on the outer corners around the batteries using the bigger star screwdriver. As a result, the back of the Zoom H2n microphone comes off. Unplug the wires connecting to the front.

4. Once the bigger screws are removed, unplug the back panel from the front half. After the back is removed, the microphone connector panel is unscrewed and removed from the front half.

5. There are two sets of microphones - Mid Side and XY. Mid Side has a 5 pin connector - the rear pair - and the XY has a 4 pin connector. Unplug these connectors from the small microphone panel.

6. Snip off the capsule holders from the base. As a result, the connectors/mics are fully detached.

7. Unsolder the connector wires from the MS and XY capsules sets, without damaging them.

TheISRO_BrahmaAmbisonicMicrophoneTutorial_Step7.2

8. Color of the wires and terminals to microphone capsules.

Mid side microphone M + brown, - right S + orange - yellow XY microphone X Green +, blue - Y purple + grey - (color code may vary, must be checked individually)

9. Remove the extra plastics on the Zoom H2n capsule area or cut off edges of the tetrahedron to accommodate the tetrahedron array inside the front.

10. Mark the left and right sides of the tetrahedral array and make sure it fits inside the front panel.

11. Insert the wires of XY microphone [yellow/ - left] through the bottom side of the tetrahedral array from the left side and solder it to one of the 14 mm capsules and similarly to the right side [red]

12. Insert the wires of MS microphone [blue - left] through the same side of the array where the left wires of XY microphone were inserted, so the wires don’t get entangled. And similarly to the right side [black/white] (Note: There are high chances of positive and negative wires getting mixed up - cross-check it with a multimeter)

13. Press the capsules inside the tetrahedral array until they are nicely fit.

14. Insert the connector that connects the amplifier and microphone in the front panel.

15. Insert the tetrahedral array with the capsules mounted with the left side down (front of the array) inside the front panel and pull the wires from one side and place the 4 pin and 5 pin connectors in their corresponding places.

16. Plug the connector wires of the back to the front to attach the battery compartment. At this point, turn on the recorder and check that all four channels are working. The front pair (XY) faces towards the back of the recorder! When you are recording, you can see the meters which would normally be the front, but now is the rear.

17. Screw the big and small screws back in their places and close the recorder.

In our next series, we will cover calibration of the microphone and using it for acoustic measurements.

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