To the average person, it would seem that all microphones are created equal – “you’ve seen one, you’ve seen them all,” or “a mic is a mic.”  But to anyone who is exposed to life in the pro audio world, it quickly becomes apparent that there are a multitude of different types, designs, shapes, sizes, and uses for the myriad of microphones available to the sound engineer.  We will try and explore a few of the different designs available, and their respective practical uses.  For the purposes of this brief commentary, we will try and focus on the more general aspects of microphone design and uses, rather than trying to recommend any specific mic. brands or models offered.

A brief explanation of the mechanics of mic. design:

Microphones generally fall into one of two design categories. They are considered to be either “dynamic” or “condenser” (which determines whether they are “passive” or “electronic” in design). A dynamic mic. is passive in the sense that it does not require a power source to function, but instead uses the air pressure  that naturally occurs when a sound is produced, to move a diaphragm attached to a  coil surrounding a magnet, which generates an electrical audio signal  (this requires no other power source to operate).   A condenser mic., on the other hand, uses a capsule with a diaphragm that is electrically charged, and generally requires the use of “phantom power” (supplied by the audio console) to operate.  This is just a cursory explanation of the differences in these two designs but should suffice for our purposes here.  The important thing to remember is that the differences in these two designs has a marked influence on the way these mic.s perform, and therefore, influence the ways they are used.

Dynamic microphones  are typically less sensitive to loud sound sources, are slower in their transient response, less accurate, more limited in frequency response, and generally more rugged (less fragile) than condenser mics.  This makes them especially well-suited for use on drums, guitar amplifiers, and screaming singers!

Condenser  mics., on the other hand, are generally considered to be more sensitive to softer sounds,  more accurate, and are quicker in transient response. This makes them a good choice for softer, broader range sources, such as vocals, acoustic guitar, drum overheads, acoustic stringed instruments, choir, etc.  They tend to be a bit more fragile, with less-tolerance of moisture and rough handling.  Because condenser mic.s are more sensitive than dynamic mics., they often have a more limited dynamic range, which means that some of them have a tendency to overload or distort more easily than dynamic mic.s do. There are some exceptions with some of the late-model condensers, which are designed specifically for drums and other loud sources, so the lines have been blurred a bit in recent years. Still, it’s something to keep in mind when choosing the right mic. for the job.

This brief explanation of the “mechanics” of dynamic and condenser microphones has hopefully begun to shed some light on which type of mic. design might best suit the type of sound-source and environment.  However, the there are still more things to consider when choosing the right microphone for the job.  A few of these are microphone pick-up patterns, frequency range, frequency linearity or irregularities, dynamic range, and capsule orientation.

Pick-up patterns:

With the exception of studio microphones, most microphones are designed to have a single pick-up pattern. This pattern is designed into the capsule, and it determines the narrowness or width of mic. sensitivey to sounds arriving from different directions.  The most common pick-up patterns are cardioid, hyper-cardioid, and omni-directional.

A mic. with a cardioid (uni-directional) pick-up pattern  generally has a high sensitivity to sounds arriving directly into the capsule, while rejecting (or attenuating)  sounds arriving off axis (or from directions outside the mic.s prescribed pattern). A mic. with a hyper-cardioid pick-up pattern has an even narrower field of sensitivity, which makes it even less sensitive to  sounds arriving outside of the area directly in front of the capsule. A mic. with an omni-directional pick-up pattern has a very wide field of sensitivity (usually about 360 degrees)  and therefore is equally sensitive to sounds arriving from all directions.

These differences in directional sensitivities allow for creativity and control over what sounds the mic. will pick-up, which is a very important factor when choosing the best mic. for the job.  For most live productions, the use of omni-directional microphones is prohibitive because of a greater possibility of feedback problems. Subsequently, in most cases, cardioid and hyper-cardioid mic.s are most often used for live sound reinforcement.  There are some exceptions, as in the case of headworn mic.s and lavalier mic.s for the spoken voice, but this is one of the few exceptions (in my experience).   Omni-directional mic.s are usually relegated to the recording studio, where acoustics are controlled and feedback is not an issue.  Additionally, many studio mic.s have the ability to switch the pick-up pattern between hyper-cardioid, cardioid, omni, and figure-8 (figure-8 is too hard to describe here -  google it!), making them a very flexible tool, indeed.

Another thing worthy of mention is that some mic.s are designed with the capsule facing forward, and others have the capsule facing to the side.  This allows the mic. to be physically oriented to best capture the voice or instrument (another important thing to know about the mic.s in your collection).  This is not always as visually obvious as it would seem (CHECK THE SPEC.’S or ASK SOMEONE, IF IN DOUBT).

Mic. personalities:

Although, it is imperative to know the pick-up pattern and mic. design-type, it is equally as important to know the individual sonic signature of each mic. in your arsenal. Microphones have as many sonic colors, personalities, and quirks as people do. Though there are some mic.s that have a ruler flat frequency response, most have unique sonic properties that make them more(or less) suited for specific tasks or instruments. For example, a mic. might be considered “bright” in character, meaning it tends to accentuate the high frequencies, or “dark” because it de-emphasizes the high frequencies (or accentuates the low frequencies). Microphones often have peaks and valleys in their frequency response that can be used to shape the instrument (or voice) at the source of the sounds being amplified. In other words, before the sound has the chance to be heard, it is already being influenced by the sonic personality inherent in that particular mic. design.

In some cases, it is desirable to have a mic. with a perfectly flat frequency response in order to capture an absolutely accurate representation of the sounds being picked-up by the microphone. By default, these highly accurate mic.s are found exclusively in the condenser mic. category, and tend to be much more expensive than other mic.s (no doubt because of very strict standards for design and manufacturing). For a variety of reasons, these sensitive and highly accurate mic.s are mostly used in the recording studio or as a diagnostic measurement tool. Though one might wonder why we wouldn’t want all of our mic.s to be perfectly accurate, the fact is that the frequency-response anomalies found in most mic. designs is yet another way that we can creatively shape or control the sounds we are trying to capture.

By being familiar with the sonic differences in each  mic., the experienced sound engineer can make informed creative decisions about which mic. is the best one for the job. This is just one of the many ways that sound engineering is both an art and a science.

Apart from these basic distinctions, microphone choice is largely a matter of personal experience, trial and error, or the recommendations of others.  Get to know them and they will serve you well.

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This entry was posted on Friday, February 12th, 2010 at 9:26 am and is filed under Gearheads. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.