Microphone Choices:

Selecting the Right Microphone for Your Own

MP3 Recordings

In past issues of Shure Notes, we've covered the subject of choosing the right mics for recording. Since this issue includes ten MP3 recordings, we decided to hit the replay button.

A Word About MP3 Files
The key to a quality MP3 is a quality recording. MP3 uses a "lossy" compression scheme to reduce the size of the audio files, which means that bits of the sound are thrown away, or "lost." What this means is that, while the differences are slight, a less than ideal recording will be degraded even further by the MP3 encoding process. With that being the case, it's important that you use whatever means necessary to achieve a high-quality recording.

Microphone choice is highly dependent on the voices and instruments you are recording, as well as the style of music. If you use an inexpensive microphone that doesn't capture your sound the way you envision it, no amount of "tweaking" later on in the recording process will restore it. At the very least, a decent quality condenser microphone and a couple of multi-purpose dynamic microphones will get you through most general recording situations.

But remember, mic technique is largely a matter of personal taste - what sounds right for players, instruments and the song is right. There are no absolutes here - just helpful guidelines.

1. Choose a microphone with the right frequency response
for the instrument or voice you're recording.

Every microphone has a specific frequency response.

The Shure KSM137, for instance, is a good choice for keyboard, percussion, and string instruments.

2. Place the microphone at various distances and positions
until you get the sound you want. If you don't like it:

• Change the position
• Further isolate the instrument
• Change the microphone
• Change the sound of the instrument
  (for instance, replacing worn out strings on a guitar)

3. Eliminate poor room acoustics and unwanted sounds by placing the microphone as close as possible to the loudest part of the instrument to isolate the sound better. Selecting a microphone with a tighter pick-up pattern may also help.

Studio recording is different from the world of live performance, but mic characteristics are the same. In the studio, you want the control and freedom to isolate certain instruments - and since there aren't live loudspeakers to contend with, feedback isn't an issue.

Selecting a Microphone

There are basically three considerations in choosing a mic for recording (or any other purpose) - operating principle (or transducer type), frequency response and directionality (also called polar or pickup pattern). Here's a quick review.

1. Operating Principle

Inside the microphone are transducers - mechanisms that turn sound waves into electrical energy. It's important to understand the nuances between the two most common types because they handle and capture sound differently.

Dynamic
A simple, rugged diaphragm/coil which sits inside a magnetic field. It handles extreme volume levels without distortion.

Condenser
A lightweight, sensitive diaphragm that moves in an electric field to precisely and smoothly capture sounds. It requires a power source, called phantom power, from the mixer or microphone preamplifier; a few models can also be battery powered.

2. Frequency Response

Every microphone has a signature and part of that signature is its Frequency Response. Frequency response determines the basic "sound" of the microphone. It is determined by the range of the sound (from lowest to highest frequency) that a microphone can reproduce and how that sound varies at different frequencies.

Animation: The most common response curves you are likely to see are flat and tailored. When you look through catalogs or web pages, you're probably going to see icons that look something like these.

3. Directionality

There are two basic types - omnidirectional and unidirectional.

This is the symbol associated with an omnidirectional mic. It is sensitive to sounds from all directions.

Best to use when more room ambience is the goal. Direct and ambient sound can be adjusted by moving the mic closer to or further from the sound source.

This is the symbol most often associated with unidirectional microphones. These are sensitive to sound coming from only one direction - let's say from a guitar amplifier. The most common type of unidirectional microphone is called a "cardioid" because its pickup pattern is heart-shaped. It picks up most sound from the front of the microphone and some from the sides.

supercardioid or hypercardioid microphones offer even greater sound isolation through narrower pickup patterns.

Most unidirectional microphones exhibit a characteristic called proximity effect. As the sound source is moved closer to the microphone, especially within 12" of the microphone, the bass response increases. This effect can often be used artistically. But when a more natural sound is needed for your recording, roll-off the low frequencies at the mixer, use a microphone that minimizes the proximity effect, engage the low frequency roll-off switch if available, or substitute an omnidirectional microphone (which does not exhibit proximity effect).