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Coherer with mechanical feedback

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I had this idea long ago. Using a rubber tube coherer that makes some noise. Amplifying the noise and driving a loudspeaker with it. The coherer is mounted on the loudspeaker. Thus we get a closed loop. Today I realized this setup with a pair of active PC loudspeakers.



The coherer is mounted on a cork that is glued to the cone of the loudspeaker.

I could regulate the coherer bias with a potentiometer. Of course the circuit very easily gets kicked into self oscillation. The trick is to keep the bias so low that it is just before self oscillation.

The signal contains burts and areas where the signal is more calm and continous.





I recorded the signals with a microphone in Audacity and applied  Paulstretch and denoising.



The following samples are doubled. At the beginning aou will hear the raw signal and afterwards the same signal processed.


The results are not groundbreaking but definetly better than the ones I gained with a static coherer.


Double_Ich hör.mp3

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  • 4 weeks later...

Thank you! I did a lot of experiments with coheres in audio ITC with various materials like iron, nickel or silver filings, also copper and aluminum. The most valuable results I got with graphite powder. However I have not posted yet the results of these experiments I did 2 years ago.

If you are interested in coheres you also might take a look at this: Coherer Mill

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  • 3 months later...

Yes, Particle Coherers can be accused of having a sort of low-lever Microphone capabilities. Andres has published somewhere on here a basic water Coherer that I cannot see as having any sort of Microphone tendencies. I guess Particle Coherers will need to have to be built into a sound proof box, because they do show a lot of usefulness in ITC work.

In High School, I did build a Microphone using Graphite Rods ripped from huge 3v Dry Cells, that was remarkably sensitive.

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Sure but having just a possible susceptibility for acoustical signals does not mean that they play a role in your setup. In my experiments I was sitting in silence when the coherer was running. But even with talking near the coherer in rare cases I never recorded my own voice. If you listen to the coherer signal you will see that you get a constant stream of speech. The problem is that the signal is much distorted and partially below noise level.

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