Microphone Mysteries Revealed, by Ted Hunter, Sweetwater Sales Engineer.
A: In general (and I think it’s important to preface this with “in general” because there are certainly exceptions to every rule) a condenser microphone will have greater sensitivity and “more” extended top end (and sometimes bottom end) frequency response than a dynamic microphone. This is due to the way a condenser microphone converts sound to electricity. The diaphragm in a condenser microphone is very thin; as it vibrates, the potential between the diaphragm and the backplate of the capsule changes. The changing voltage is then amplified by the pre-amplifier (the one built into the microphone, not the one that’s in your rack, mixer, or interface, which should actually be called a “mic amp,” but that’s another story for another inSync article). Since the mass of the diaphragm is so small, the microphone is very sensitive and responds to “smaller” (shorter wavelength), or higher frequencies very well. In fact, many condenser microphones are capable of picking up frequencies well beyond what we can hear.
Dynamic microphones, on the other hand, produce signals by the motion of a conductor within a magnetic field. Typically, when we talk about dynamic microphones, we’re actually talking more specifically about moving-coil dynamic microphones, in which case a coil of wire is attached to the diaphragm of the microphone and suspended in a magnetic field. That’s a lot of mass to move, which means lower sensitivity and less high frequency and transient response. Ribbon microphones are also dynamic microphones; the difference between a ribbon and a moving-coil microphone is that a small strip of metal takes the place of both the diaphragm and coil of wire. The strip of metal itself is what induces the current in the magnetic field as it vibrates; as there’s less mass to move, there’s also more high-frequency response than you have with a moving-coil microphone (although not as much as there can be with a condenser). Dynamic microphones are also less sensitive than condensers since there are no active electronics to amplify and buffer the signal, so they typically require more gain than condenser microphones and their sound will vary more from preamp to preamp. This usually isn’t a problem, since dynamic microphones are typically used on louder sources, but it can be a problem when they’re used on quieter sources. With ribbons it’s often critical to have a mic amp with enough gain to boost the signal to a useable level. There are a few dynamic microphones on the market with preamps built into them (such as the Ball moving-coil from BLUE and the R122 ribbon from Royer) so they can be used more successfully with a wider variety of preamps.
If you look hard enough you’ll see just about every type of microphone used in just about every type of situation. Typically, you’ll see moving-coil dynamics used on louder sources (guitar amps, up close on drums, live vocalists, brass, etc.) and condensers are typically used where a more natural or even extended high-frequency response is required (such as drum overheads, pianos, acoustic stringed instruments, studio vocals, orchestral and ensemble recordings). Ribbon dynamics are becoming more and more popular with digital recording since they do a great job of taking the “edge” off of things, especially, in my experience, percussion and brass. They’re also very popular on guitar amps, acoustic instruments of all kinds, and even vocals.
Finally, please remember that the “in general” from the first paragraph still applies. Sure, there are plenty of live vocalists who use condensers, and studio vocalists who use dynamics, and condensers are often used as close microphones on drums and guitar amps. And, although you’ll rarely see a moving-coil dynamic recommended for drum overheads, acoustic guitar, or classical recording, there are no rules; plus, all condensers and all dynamics certainly don’t sound the same. But understanding how we should expect a particular microphone to sound and why it might sound that way can certainly make it easier to select the appropriate microphone for the job – even if it’s not the microphone that’s “typically” used for that job!