List of Parts
- 1x male XLR plug
[Alternatively any other connector able to ‘carry’ phantom power from the recording device to the condenser microphones can be used.]
- 2x 6mm (omnidirectional) condenser microphone elements
- audio cable
- short piece of thin, two wire cable
Prepare the audio cable on each of its ends by stripping off a short part of the protection around the wires, leaving the bare copper of the positive and negatire wire free, while cutting off the wire of the ground/shield. On one end of the audio cable, solder the wire carrying the positive signal to pin two (2) and the wire carrying the negative signal to pin three (3) of the male XLR plug.
For more information onn how to solder XLR connectors, please see the blog about DIY Piezo Pick-ups.
Carefully solder the positive wire of the additional thin, two wire cable to the positive part of the condenser, and the negative wire to the negative connection. This is a delicate procedure and requires a thin soldering iron. If the condenser microphones are exposed to the heat from the soldering iron for too long, they will break.
At the end, put the heatshrink over the other end of the thin wires, then solder the thin wires to the audio cable. Before applying heat to the heatshrink, test the cables by plugging these into a recording device. Remember to switch on phantom power for the test. If the condensers work fine, move the heatshrink around the soldering point of the cables and warm it in order to protect their connection.
Next, use a sharp knife (carving knives are good for this) to create space for the condenser microphones, fitting one each into the earpieces of the stethoscope. As long as the holes are not too big, the condenser microphones will hold all by themselves (no glue was needed for the example stethoscope here).
The last step is to test the finished stethoscope-microphone again by plugging it into the recording device and searching for the best, subtle sounds to capture.
Because of the monophonic nature of the stethoscope it is entirely justified to combine the thin wires both condensers and solder those to their respective wires on the audio cable—using only one XLR plug into a recording device.
In this experiment the material of the stethoscope itself was to be tested, if it would change the captured sound comign from each one of the microphones. Therefore one XLR plug had been soldered to each condenser microphone.
Here some recordings:
Rain (on metal roof):