How to Test a Microphone with a Multimeter

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Your studio is now fully set up, and you decided to begin recording. You begin singing, then check your recording, only to realize that each word you say sounds muffled. You check your microphone and can only think about what happened. 

Why would your mic sound muffled? You will find many potential reasons why that could occur. A broken microphone could be extremely stressful at the very least. Getting it fixed at a repair shop or when the device is out of warranty could cost more than the device itself. Fortunately, replacing or fixing a microphone on your own could be done in just a simple step. 

What is a Microphone? 

Microphones look different from loudspeakers, and that’s why most people don’t realize how similar they are. In a loudspeaker, electricity follows into a metal wire coil covered around a permanent magnet. The varying electricity pattern produces a magnetic field all around it, which pushes over the field the permanent magnet produces. That makes the coil move. 

The coil connected to a flat disc is referred to as a cone or diaphragm. It moves when the coil moves. The moving diaphragm sends air back and forth into the room and makes sound waves you can hear.

On the other hand, you will also find most identical parts in a microphone, but they work reversely. 

How Does a Microphone Work?

Every time you speak, sound waves produced by your voice bring energy toward the microphone. Keep in mind that sound you can hear is energy passed by vibrations in the air. 

The diaphragm inside the microphone travels back and forth when the sound waves hit it. The coil connected to the diaphragm also moves backward and forward. 

The permanent magnet creates a magnetic field, cutting through the coil. An electric current flows through it as the coil moves from side to side through the magnetic field. Further, the electric current flows out from the mic to a sound recording device or an amplifier. 

What Are the Causes of a Bad or Faulty Microphone? 

Just like any other equipment, a microphone can break. However, what are some of the common factors, which cause these devices to get bad? 

  • Smoke and dust

Letting smoke and dust build up on your mic is a surefire way to get it damaged. In particular, dust is very lethal as they seep into the mic through the head basket and settle permanently on the diaphragm. 

Further, dust could obstruct the movement of the diaphragm by choking it. That will lower the diaphragm’s sensitivity and will surely impact your microphone’s performance.

  • Humidity

Do you often use or keep your mic in a humid place? Well, it is about time you put a stop to it forever. Take note that humidity is the culprit as to why many mics are damaged. Are you wondering why?

Every time humid air falls on microphones, the vapor converts back into a liquid. That liquid could seep into the mic through its head basket. Moreover, humidity could be in the form of saliva from your mouth into the microphone while you use it. 

Electronic parts are at the greatest risk of getting damaged when the liquid gets inside the microphone. Components such as the Field Effect Transistor (FET), converters, and inbuilt circuit boards inside will be damaged with such exposure to liquid.

  • Mechanical stress

The term above might be a broad one for many things, but we’ll try to make it as easy to understand as possible. 

Remember that mics nowadays are designed to last a lifetime. Most manufacturers aren’t frightened to provide you with more than five years of warranty on their mics, as they think it’s strong enough to deal with any impact.

Nonetheless, once those microphones are exposed to many impacts such as drops, the built-in will start to get loose. Later on, the device will stop functioning well. 

Another critical part of a mic prone to mechanical stress is the diaphragm—a small membrane vibrating as sound waves hit it. Just visualize how lightweight they are when sound waves move them. 

Is your microphone often exposed to mechanical stress? In no time, its diaphragm might be the first one to be damaged. That would render your device totally useless until you decide to buy a new one. 

How Do You Test Your Microphone? 

There’s no doubt that mics are good devices we need for recording sounds. However, there are times they go bad and fail to record accordingly, if at all. How do you test a mic to see if the mic itself is the cause of the problem or because of circuit issues? 

In that case, you can use a digital multimeter. Follow the steps below to check your microphone:

  1. Please turn off the power source of the microphone and dismantle it carefully. If you don’t know how to do that, you can watch videos of its disassembly process online.
  1. Remove the mic. 
  1. Grab your digital multimeter and set it on the resistance setting. The Ω symbol might designate that. Keep your setting on 20 K or 200 K ohms setting. 
  1. Touch the tip of the two lead probes of your digital multimeter (the black and red wires) to the two terminals or pins of the microphone. 
  1. Move your mouth near the mic and blow some air into the holes. 
  1. If the screen’s reading increases fast, your mic is good and well. In many microphones, the reading increases to at least 100. If your reading is still one after blowing some air, it means your microphone is bad and faulty.

Final Thoughts

An easy way to determine if your mic is damaged is to inspect the internal parts for any potential damage signs. You can also do the tests we highlighted above to determine if there have been any possible changes compared to the mic’s specifications.

A digital multimeter is one of the best tools you can use to troubleshoot your microphone. We hope you find this article highly informative and helpful. The next time you believe your mic is having problems, feel free to revisit this page.

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