Sunday, August 26, 2018

A microphone directly connected to headphones


At your risk. Protect your ears.


It is possible, sensitivity of course will be low.


A 200Ω microphone can be directly connected to 300Ω headphones for example. If the headphones are connected in parallel resultant impedance becomes 150Ω.


So it is almost impedance matching, ie max power transfer. A 200Ω microphone feeding an 150Ω load.


We could hear as loud as seeking to our ear but it is the power inefficiency of microphones and headphones. Energy is lost to heat etc.


So even if gently taping the microphone, little sound can be heard.


But it should be top quality. As it is straight cable with no gain.


A similar experiment can be done by connecting two 8Ω say 5in full range drive unit speakers together.


We can gently move one by hand and see the other cone moving.


A great experiment to understand the law of induction.


And Lenz's law or the law of conservation of energy.


If we gently tap the paper cone of an unconnected speaker we can hear the vibration step response of the cone.


If we then short circuit the terminals we almost hear nothing. The short circuit at the voltage output we have generated by our hand taping acts as a break.


Possibly in the same way a metro train or tram breaks by feeding the output generated by its motor back to the system possibly heling another metro train to accelerate in real time.












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