Mic Basics: What Are Transducers?
Editor's Note: This post was originally published on February 23, 2009 and updated on July 6, 2017.
Edited Transcript
A microphone does one simple thing – convert sound into an electrical signal so it can be amplified, recorded, or transmitted. The transducer is the part of microphone actually detecting and converting the sound waves. This is also sometimes called an element.
There are many different types of transducers. Each one offers a different tonality and other important characteristics you should know before selecting a mic for a particular application.
How does a Dynamic Microphone Work?
By far, the most widely used transducer is in dynamic microphones. It's a very simple design consisting of a diaphragm, a voice coil and a magnet. If you've ever seen a cutaway picture of a loudspeaker, that's kind of what a dynamic microphone element looks like.
The way it works is simple: Sound waves strike the diaphragm and cause it to vibrate back and forth. The voice coil, which is a small bit of wire attached to the back of the diaphragm, vibrates back and forth along with the diaphragm. A field created by a small magnet surrounds the voice coil. When the voice coil moves, the magnetic field generates an electrical signal in the wire, which corresponds to the sound.
Dynamic mics provide very good sound quality and can handle extremely high levels without distorting. In fact, Shure engineers have calculated that it would take a sound pressure level greater than 150 decibels to cause distortion in a typical SM58 dynamic microphone.
Dynamic mics are also great because they can tolerate a lot of rough handling, as well as extreme temperature, humidity and moisture. There is, in fact, very little you can do to ruin a dynamic microphone short of simply submerging it directly in water. But in some cases, a hearty dynamic mic can even survive that sort of dunking!
How does a Condenser Microphone Work?
Another popular transducer style is found in a condenser microphone. These transducers use a thinner diaphragm with an electrically charged back plate instead of the voice coil and magnet setup of a dynamic mic. When the diaphragm of a condenser mic vibrates, it alters the spacing between the diaphragm and the back plate, which creates an electrical signal corresponding to the sound.
One of the advantages of a condenser mic element is that it has much less mass than a dynamic element. So it's far easier to move it in response to subtle sounds or high frequencies. Condenser microphones, however, do require a power source to operate. This can come from a battery inside the microphone or it can be fed through the microphone cable from the mixer or recorder as so-called "phantom power."
Most condenser mics can work with a range of voltage, usually from 12 to 48V. Some professional studio microphones might need the highest voltage. If you plan to use a condenser mic, check your mixer or your recorder to make sure that the input supplies phantom power.
Condenser microphones are typically more sensitive than their dynamic counterparts and they're better at picking up high frequency detail and percussive sounds. This makes condenser mics the best choice for acoustic guitar, stringed instruments, cymbals, etc. Condensers are also great for recording nature sounds or sampling sound effects.
Condenser transducers can be made very small, so microphones that have to be as small as possible, like lavalier, headworn or thin gooseneck models you'll see on a podium, are almost always going to be condenser mics.
Compare Dynamic and Condenser Microphone Recordings
Hear the differences between dynamic and condenser mics by listening to the recordings below.
