Reviewing Microphones
by Phil Gates

This month we’re going to re-visit microphones. I just had a day where I sat listening to a CD recorded by a buddy of mine. He’s been working very hard over the last year or so on his production techniques. He’s gotten a lot better at sound mixing and recording. He went and bought a whole new computer rig with all of the bells and whistles you could ask for. Plug-ins for days, new speakers, the whole kit.

Yet as I sat there, listening to cool music with lifeless vocals, I couldn’t help but wonder about how he approached recording the vocals. So I asked one simple but telling question: “Hey man, what mic did you use for vocals on this song?” As I watched the blank stare creep onto his face, I knew what was going on. “Oh, I borrowed it from a friend of mine.” He had no idea.

Now I’m not being a label crab here. I could care less if he knew what brand the mic was. What bothered me was that he didn’t know what KIND of mic it was. Cardiod, Omni, Condenser, are not words in his vocabulary, and they should be to any person that’s going to hit the record button. So let us review:

Types of Microphones

What’s the difference between a dynamic and a condenser microphone?

Dynamic mics are much like the name implies. The dynamic mic process involves the diaphragm, the coil and the magnet. It is the dynamic pressure of your voice (or source) against a Mylar diaphragm that creates a movement in a thin wire coil that is suspended in a magnetic field created by the magnet. This movement of the coil crossing the magnetic field is in direct proportion to the original volume and frequency of the voice or source. There is a magnetic flux created by the coil and the magnet that is now an electrical signal. This signal can be sent to the wire leads that are the connection pins at the bottom of the mic. This electrical signal can then be recorded.

A Condenser mic in its bare form is a capacitor. A capacitor has the ability to store an electrical charge. Condenser is actually the original name for capacitor, and has stuck as a name when it comes to mics. Instead of a Mylar diaphragm hooked to a coil moving through the field of a magnet, like the dynamic mics, this technology uses two thin plates microns thin, usually plated with gold, or spattered with gold. These plates are called the capsule. They are sealed to each other with an air-tight gap between them. One of these plates is free to move, and the other is not. An electrical charge is placed across both plates (one plate to the positive side of the charge, the other plate to the negative side) and this sets up a nominal state of electricity. Meaning that as the mic rests with no sound, there is a balance of electricity set. As sound pressure hits the flexible plate, this changes the air gap density, which then changes the electrical balance. It is the change in this electrical balance that is directly proportional to the audio source’s volume and frequency. Because this whole arrangement of electronics is a very low signal at the output, a preamp is usually built in to make the level hot enough to be of use. This electrical signal is now present at the connection pins at the bottom of the mic and can be recorded. Pretty cool, huh?

The sensitivity of the Condenser mic makes a great candidate for the most subtle or expressive of sounds. Things where the volume of the source is maybe not that loud, but has a lot of texture and nuance to it, such as the human voice, stringed instruments, pianos, some horns, and even cymbals.

Microphone Patterns

What do the different mic patterns mean?

On most mics there is a symbol for either the one pattern that it is set for, or it can show different symbols for the different polar patterns available for that mic. A Polar Pattern is the effective pattern of what the mic could pick-up if you were looking straight into the capsule or diaphragm of a mic.

The usual suspects in the patterns are:

• Cardioid
• Bipolar (also called figure 8)
• Omni

Cardioid Polar Pattern

The Cardioid pattern is aptly named after its cardioid, or heart-like pattern (Fig. 1).

Fig. 1

What this means is that in front of the mic you get good response from the mic, but from behind the mic there’s hardly any response. The horizontal line is the line between the front of the mic, and the back of the mic. On a hand held mic, you would hear your voice fine, but not your hands holding the mic. Your voice would be in front, and your hands behind the diaphragm.

Bipolar Pattern

In the bipolar pattern, usually this is the result of two capsules placed back to back in one housing. Called the dual capsule mic, you can have combinations of patterns from each capsule. For instance, the Bipolar pattern is two cardioid capsules back to back to create a pattern like this (Fig. 2):

Fig. 2

This polar pattern can be great for a duet, where both singers are facing each other and singing at the same time. The position of the condenser mic is vertical on top of a mic stand, so each person would be picked up. Sounds off axis, to the sides of the mic, would not. So if the singers wanted to hold lyric sheets to the side, they could without having to worry about paper noises getting recorded. In this pattern, sounds in front and behind the capsules get picked up, but not from the sides.

Omni Polar Pattern

The third of the polar patterns we’re going to discuss is the omni polar pattern. This one is very easy as it just picks up everything from every direction. Many lavalier mics are omni polar patterns, so that the mic can move with the person, and still catch all of the voice. This pattern looks like this (Fig. 3):

Fig. 3

As you can see, there are no restrictions. There are smaller definitions of these three polar patterns, but primarily, these are the main types of polar patterns. When deciding what mic to use, this is definitely one of the aspects to consider. Typical mics and uses may be: For potentially high volume sources, like guitar amps, snare drums, trumpets, etc, suggestion would be a dynamic mic. For more subtle things like vocals, pianos, ambient mics, overhead cymbals, stringed instruments, a suggestion would be a condenser mic.

So now we have reviewed.

Please try the mic you have in as many ways as possible to capture your sound sources.

Have fun,
Phil Gates

http://www.philgates.com
www.myspace.com/philgatesmusic