Turning Sound into Signal

In the world of live sound, there are few things more ubiquitous than the handheld microphone. A long cylinder, a mesh ball—you’ve seen countless models and they all look similar. Underneath that mesh, however, hide some major differences in how microphone transducers turn sound into signal.

“Transducer” is a fancy word with a simple explanation: any device that turns one form of energy into another. When it comes to music and audio, nothing has greater effect on the quality of sound than the transducers used. 

What turns mechanical vibration into sound? A rather important transducer called an instrument.Sound into signal? Transducer #2: the microphone. 

Signal back into sound?  Transducer #3: the speaker. These are crucial links in the audio chain.Handheld mics use one of three dramatically different transducer types in their elements: dynamic, condenser and ribbon. Each technology affects how the mic sounds, how it interfaces with other equipment, how rugged it is and more. Dynamic and condenser models outnumber ribbon designs 1,000 to one in real-world applications, so we’ll focus primarily on those.

The dynamic element

The simplest microphone technology—dynamic—is also the most common. Dynamic microphone elements work like a tiny loudspeaker in reverse. In a speaker, current flows through a coil of wire suspended in a magnetic field. The material (i.e., speaker cone) attached to that moving coil excites the air and makes sound.

A dynamic mic has a suspended circle of material attached to a coil of wire. When sound moves the material, the coil of wire moves through a magnetic field and creates current.Because a dynamic mic element is little more than a circle of material, a magnet and some wire, there’s very little to go wrong. This makes the dynamic mic very rugged, and nearly impervious to harsh environments. There’s a running joke that a contractor can drive nails with a dynamic mic during the day and sing into it at night. Exaggeration aside, dynamic mics rarely fail even when dropped, thrown, hit with drums sticks, or used to hit drums themselves.Because the dynamic element has the added mass of wire attached, it’s somewhat slow to respond to the onset of sound. This affects the dynamic mic’s ability to pick up the sharp transient of some sound sources (i.e., high-pitched percussion), and also curtails high-frequency response. This means dynamic mics generally have a slightly less open or “detailed” sound as compared to condenser designs.Dynamic mics generate enough signal to drive a mixer’s preamp without internal amplification. This means no battery to die, no phantom power, and the assurance that a dynamic mic is always “on.”

Though there are always exceptions, here are a few general pros and cons:

PROS

  • Rugged
  • reliable
  • inexpensive
  • no power required

CONS

  • Slower transient response
  • less detailed sound

The condenser element

Condenser mics use the electrical principle of capacitance to generate sound. Sound vibrates a thin membrane stretched above a backplate, and the changing gap between them results in a tiny signal. This signal is much too small to drive a cable and mixer input directly, so the condenser mic has to have internal electronics to boost the signal.

These electronics require power, so condenser mics need to have a voltage source in the form of an internal battery or “phantom” power from the mixer.The actual moving parts of a condenser mic weigh a tiny fraction of those of a dynamic design (no coil of wire here). This makes the condenser element much faster to respond to the onset of a sound, hence the mic is better at capturing fast transients and high frequencies. For this reason, condenser mics are generally considered to offer a more detailed, “open” response. Most studio recordings are captured with condenser mics because of their increased accuracy and sensitivity.Though once considered more delicate than dynamic designs, condenser mics have moved out of the studio and have proven themselves reliable enough in live sound applications. That said, condenser mics still have more internal components to fail. Their need for external power adds one more potential problem spot. Condenser designs are often more finicky about temperature and humidity.

PROS

  • potential for more detailed sound
  • faster transient response
  • better high-frequency response

CONS 

  • more components to fail
  • require power source
  • more finicky about environment

The ribbon element

The ribbon handheld mic design is similar to a dynamic microphone in that sound is picked up without the need for internal electronics. Instead of a coil of wire, the ribbon mic suspends a long, thin ribbon of metal in a magnetic field. Sound vibrates the ribbon, and a signal is created.Though ribbon mics used to be the most fragile of all mics, new materials and methods have improved their durability to match that of the other designs. Ribbon mics traditionally have a more muted high-frequency response and a smoother sound, which is a match for some (but not all) voices. Only one manufacturer (Beyerdynamic) currently makes handheld ribbon designs, and they command a premium.

PROS

  • Smooth, “warm” sound
  • no power required

CONS

  • Very few models to choose from
  • expensive

Decisions, decisions

Especially in the realm of dynamic and condenser mics, the differences between element types are starting to blur. Advances in technology and methods have resulted in a market that’s full of great-sounding dynamic mics and rugged, reliable condensers. The prospective mic buyer just needs to decide on 1) manufacturer, 2) element design and 3) budget. Give some representative samples a listen, and you’ll soon be ready to add excellent new mics to your locker.



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