Loudspeaker as a Microphone

Posted on Apr 6, 2012

This circuits allows you to use a cheap loudspeaker as a microphone. Sound waves reaching the speaker cone cause fluctuations in the voice coil. The voice coil moving in the speakers magnetic field will produce a small electrical signal. The circuit is designed to be used with an operating voltage between 6 and 12 volts dc. The first transistor operates in common base mode. This has the advantage of matching the low input impedance of the speaker to the common base stage, and secondly has a high voltage gain.

Loudspeaker as a Microphone
Click here to download the full size of the above Circuit.

The second stage is direct coupled and operates in emitter follower. Voltage gain is slightly less than unity, but output impedance is low, and will drive long cables. Speech quality is not as good compared to an ordinary or ECM microphone, but quite a

Leave Comment

characters left:

New Circuits



Popular Circuits

Peak-Reading VU Meters
R/C Airplane LED Flasher
Transmit Time Limiter
Window Comparators
Handy Pen Torch circuit
traffic light
stereo balance indicator
rotating flashing 230v lights
motorcycle alarms numbers
IR reflex
Fast response time of the control transistor circuit b