“When I look at the proposal for this system, I see there are multiple mic options available. Some of it I get and some of it I don’t. Help me understand the difference between a dynamic mic and a condenser mic, and how that impacts me.”
Questions like this come up in many situations and, unfortunately, the simple answer often provided is, “Condensers are better.” Although this may be a reasonable opinion in some cases, its validity as a universal truth is questionable at best. For customers who really want enlightenment into the mysteries of audio, there are more fulfilling explanations. So let’s help them dig in a little deeper.
To set the stage for our conversation, microphones can be thought of as similar to a human voice. Although we may make generalizations about what male or female voices sound like along with how they are similar or different, we also know that every single voice is unique. The same is true with microphones. In our comparison of dynamic and condenser mics, keep in mind that every individual mic sounds different. Sometimes, even two mics of the same model number can sound slightly different, just like identical twins don’t sound exactly the same. If you ask a manufacturer why they make dozens of models of condensers and dynamics, the answer will often be that many of them are “voiced” differently.
To appreciate the general differences between dynamic and condenser mics without the benefit of audible examples, it takes a basic understanding of how some microphones turn sound into electricity. This process is the defining element that classifies a microphone as a dynamic or a condenser. Along with that, it can give us a broad idea of a microphone’s characteristics.
When we were in fourth grade, we learned a couple of things about magnets. You may recall that, if you take a wire and wrap it around a nail, then connect each end of the wire to a battery, this turns the nail into a magnet. You may also remember that the opposite is true: Pass a magnet across a wire and it creates electricity.
- Passing electricity through a conductor gives you a magnetic field.
- Passing a magnetic field through a conductor gives you electricity.
Together, these concepts are known as electromagnetic induction or magnetic induction. Remember “magnetic induction” because it will come up in many future conversations.
If you talk into an empty, lightweight, disposable cup while gently touching the bottom with your fingernail, you may feel the bottom vibrate to the sound of your voice. That’s okay, try it. I’ll wait….Try speaking at different levels with different types of sounds. Notice any changes in how the cup vibrates? This may take some experimentation to find the right cup and how to hold it.
“What do disposable cups and magnets have to do with my microphones?” Don’t worry, we’re getting there.
Inside of a dynamic microphone, there is a very thin sliver of plastic or Mylar, similar to the cup bottom, but much smaller and lighter, so it is more easily moved by the slight movements of air that make up our sound. This sliver of plastic is called a diaphragm. The diaphragm is sitting on top of a lightweight coil of wire. This coil of wire is wrapped around a small magnet (see where we’re going?). When a sound wave comes along, it causes the diaphragm to move, just like the cup bottom. The diaphragm pushes on the coil (a conductor), which moves along the magnet:
Air molecules from the sound move in, diaphragm moves in. Air molecules move out, diaphragm moves out. Air molecules in, diaphragm moves in. Air molecules out, diaphragm moves out. The diaphragm moves with the vibration of our sound. As the diaphragm moves back and forth, so does the attached coil. As the coil moves back and forth around the magnet, it makes electricity that moves back and forth, better described as positive and negative voltage. Thank you magnetic induction.
Ideally, the change in voltage exactly matches the movement of the coil, which would match the movement of the diaphragm, which would match the movement of air molecules (or sound waves). But the real world and ideals don’t always match up. The weight of the diaphragm and coil can determine how long and how much energy it takes to get moving once a sound comes along (did you try different cups and notice they each vibrate differently?). Additionally, once the diaphragm starts to move, it wants to keep going for a little bit, even after the sound has stopped. These are two examples of why our signal (sound in electrical form) may not exactly match our original sound. They are similar but not identical. They are also a clue as to some of the characteristics of a dynamic mic.
Before going into more details about dynamic mics, let’s talk about the basic inner workings of a condenser mic. Then we will compare how these differences impact our mics in the real world. Condenser is another word for capacitor, which is a type of device that can store electricity. In a condenser mic, there are two very thin plates that are held close together with an electrical charge between them. These parts of the microphones together are called the capsule. When sound comes along, it causes a plate in the capsule to move, and in doing so, changes the relative spacing of the plates. Due to principles of capacitance, which are beyond the scope of this discussion, these changes in spacing create an alternating positive and negative electrical output from the capsule that should be similar to the alternating traits of the vibrations in air.
Compared to the diaphragm in a dynamic mic, the individual plates in a condenser’s capsule are extremely light and thin. The surface on the plate of some capsules is so thin that a stack of 10,000 would be less than an inch high. They are so light that it does not take much energy to get them moving quickly. This makes it easier for their movement to correspond to the movement in air, which means the electrical output may be a closer match to the original sound wave. But there is more to the story…
A condenser mic requires additional electronics to get power into the capsule and provide some other functions. The combination of these electronics, along with the delicate capsule, results in some condenser mics being relatively fragile. Dynamics, on the other hand, are known for being rugged and well suited for use on the road, on stage or in the hands of nonprofessionals. Some dynamic mics are claimed to be suitable for use as a hammer, but this is typically ill-advised.
“So a condenser mic uses a fragile ‘capsule’ and electronics while a dynamic uses a relatively heavier diaphragm and magnetic induction. How else does this impact me?”
The weight (or, more accurately, the “mass”) of the thingy (technical term) that turns sound into electricity, along with the presence or absence of other electronics, impacts our sound in several ways.
- Output level: Condenser mics typically have a higher output compared to a dynamic on the same source. This is called “sensitivity.” It has nothing to do with crying during chick-flicks. The increased sensitivity of a condenser mic is one factor that makes people think condenser mics “hear more.” This is debatable. Condenser mics don’t actually hear more; they just put out a higher signal level compared to a dynamic mic.
When holding a microphone, movement of the hand on the mic, rings tapping against the body or even slight movements of the mic in air can contribute to audible thuds, clinks, pops, ticks and other undesirable noise coming from the microphone. This is called “handling noise.” Typically, the more sensitive the mic, the more susceptible it is to handling noise. Because condensers are usually more sensitive than dynamics, they are used less frequently in handheld situations. Some condensers and many high-sensitivity dynamics will have internal vibration absorbers to help minimize handling noise. Many condensers will have external shock mounts to minimize similar mechanical noise transmitted through vibrations in floors and mic stands. You may notice that, on some headworn mics, there is a little flexible section near the mic element. Although this can help with positioning, it also absorbs some of the noise that can be created by movement of the person wearing the mic.
- Rapid changes in level: Sound is always changing level. A cymbal hit gets very loud very fast compared to a trombone, which may slowly get louder. The first part of the sound where it starts to get loud is called the “attack.” The ability for a microphone to reproduce the initial attack is called “transient response.” Condensers typically have a better transient response. However, a dynamic may be chosen for creative purposes to “round out” the initial sound and take the edge off, perhaps worth considering during the fifth grade trombone recital.
The measurement for sound in air is called “SPL” (Sound Pressure Level). This is what some people may commonly call “volume.” Dynamic and condenser mics can typically handle high SPL at the diaphragm or capsule. However, the electronics in condenser mics sometimes have a hard time with the extra level caused by very high SPL. This can cause the electronics in the mic to distort the sound, potentially making it crunchy or otherwise unpleasant. It creates the impression that dynamic mics are better at handling very high SPL. Although this may be the case in many situations, there are ways to help a condenser in this area. Yet, the solutions sometimes come with slightly increased system noise or other tradeoffs if improperly applied. The tradeoff will be addressed in a future piece about gain staging.
The comparisons I just discussed apply only when all things are equal, which they never are. As stated earlier, every individual mic sounds different. There are also different types of mics beyond just dynamic and condenser, and there are variations of each. Sometimes the differences are so subtle that many people don’t really think there is an important difference. However, once they hear the final results of multiple, well selected and properly placed microphones working together, they understand the benefits right away. Opinions on which microphone to use in a specific application are often determined over years of experience. Time helps develop an appreciation for how a specific mic will impact the sound relative to the other sources being captured, what mics are being used on those other sources and personal preferences.
There are other factors that go into the functional differences between dynamic and condenser mics, such as powering for condensers. But this will have to wait for another time. I hope this discussion provides the content you need to supply an alternative answer to “What’s the difference between a dynamic mic and a condenser mic, and how does that impact me?” Pick and choose from our discussion here as you see fit. Then again, you can always try, “Trust us. We’re professionals.”