Focusing Sound With a Parabolic Microphone
Mounting the microphone
The microphone is what makes this project work. The first step here is to make the microphone mounting. Follow these steps:
1. Cut four 6" pieces of wooden dowel.
2. Cut a slot about one-third of the way through each dowel,
1⁄4" from an end. The slot has to be wide enough for the washer to slip into.3. Assemble the dowels and washer in the parabolic dish, as shown in Figure 6-12.
Use cable ties to hold the dowels in place. If you are doing this by yourself, it can be kind of a struggle, but it is doable. Getting another person to hold the dowels in place while you put the cable ties on it will simplify your life.
4. Solder an 18" black wire to the ground pad of the microphone cartridge and an 18" red wire to the +V pad.
Figure 6-13 shows a cartridge before and after soldering.
5. Twist the free ends of the wires from the microphone cartridge together and feed the microphone wires through the PVC fittings from inside the parabolic dish until the end of the wire reaches the 3⁄8" hole.
If you have trouble pushing the wires around the 90° turn, take a stiff wire with a hook shape in the end (we used some 10 gauge wire; many building supply stores will sell you a few feet of this) and pull the wires through the PVC fittings and pipe.6. Use a piece of 20 or 22 gauge wire with a hook shape on the end to pull the wires from the microphone cartridge through the 3⁄8" hole.
7. Pull the wires through the 3⁄8" hole, leaving enough wire inside the parabolic dish for the microphone cartridge to reach the 11⁄2" washer with about two inches of slack left over.
8. Cut the wires to allow three inches to extend from the
3⁄8" hole in the pipe and attach each wire to a right-angle phono plug, as shown in Figure 6-14. You can use either a plug that requires soldering to the wire or one that uses a screw to secure the wire, as we did here.
9. From the inside of the dish, put the 3⁄8
" inner diameter O-ring over the microphone cartridge and glue the O-ring to the washer, as shown in Figure 6-15.
Make sure you don’t get glue on the front side of the microphone cartridge, or it could interfere with any sound coming through.
10. Use another cable tie to secure the wires from the microphone to one of the dowels.