Adventures In Audio with Audio Masterclass
Do microphones need rest?

Do microphones need rest?


A question from a Audio Masterclass Newsletter reader (not a native English speaker)…

“Firstly I need to explain that all audio devices have an On/Off switch that put them to rest. But the microphone membrane is always vibrating in respect with the air movement (or should I put it: following the air pressure variations). Perhaps when not using the microphones we should stick them in their carrying cases (if any provided by the microphone producer). But even there acoustic vibrations will reach and move the membrane. So, the permanent movement of the membrane may damage or affect the quality of the microphone?”

It's a good point. It's interesting to remember that dynamic microphones pick up sound and convert it to an electrical voltage all the time, whether they are plugged in or not. And you thought you were having a private conversation…

But seriously, I have never heard anyone say that microphones need rest. Perhaps no-one has ever even thought about it until now. And if anyone has actually tried out any kind of test to see if resting a microphone makes a difference… well let us know ASAP!

So should a microphone need rest? Let's think of the dynamic microphone, which consists of a diaphragm, a coil of wire, a magnet and a transformer. And a shell to put it all in. It is difficult to see how the coil, magnet or transformer could benefit from being rested. Having said that, a car mechanic once told me that the ignition coil of a car could wear out after a time. I didn't see how that was possible, but he told me that mechanical stress eventually breaks down the insulation on the turns of the coil, shorting out more and more turns over time, thus resulting in a weaker spark. There's nothing in standard electronics textbooks to cover that!

But if anything needs rest, I would say that it would have to be the diaphragm. You could rest it in silence perhaps.

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Alternatively you could short out pins 2 and 3 of the mic's XLR connector. That would mean that whenever the diaphragm tried to move, a magnetic field would be created around the coil that would interact with the field of the permanent magnet and persuade the diaphragm to stay still. But the diaphragm would be fighting all the way – that might make things worse.

The above paragraph wouldn't apply to a capacitor microphone, so you would have to keep it away from sources of sound to rest it.

But the bottom line is that I have never heard of a microphone diaphragm, of any type of microphone, wearing out from over use. Wearing out from age and abuse, yes. But not any kind of normal sound level.

So if anyone knows differently, and I mean knows for certain, please give us all the benefit of your wisdom.

Also, if anyone has an opinion on whether mics would benefit from being rested, or any plausible explanation for why they might, we would like to know that too.

David Mellor

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David Mellor