A microphone made from a speaker has a high linearity (high precision in signal conversion). If you do not have a high-precision microphone, but you desperately need it, do not hesitate and use the speaker in an unusual quality for it. An emergency situation may arise in which you have to reinvent the microphone from available tools. For example, employees of a service radio station simply dropped the microphone and broke it. Replace it with a full-range speaker - for example, a broadcast speaker.
It is necessary
- Speaker
- LF transformer
- Shielded wire
- Metal case
Instructions
Step 1
The internal impedance of the speaker is very low compared to a conventional dynamic microphone. The voltage it develops is small, and not enough to connect it directly to the standard input of the amplifier. Therefore, it is necessary to use a step-up transformer. Connect the speaker to the low-voltage winding of the transformer, and from the high-voltage winding feed the signal to the microphone input of the amplifier. Different transformers have different high voltage winding resistances. Therefore, it is useful to provide the output winding with a variable resistance, connected according to the potentiometer circuit.
Step 2
The connection to the amplifier must be made with a shielded wire to avoid picking up noise. It is also good to place the assembled structure in a metal case with a hole for the speaker and connect the case to the wire screen.
Step 3
If you do not have a metal case suitable in size at hand, you can use the broadcast speaker of the radio point together with the case by removing the variable resistor from the speaker circuit and placing it in a high-resistance circuit as a potentiometer. In this case, you can try to use your own radio transformer.
