Input: Picking a Microphone

You configured and adjusted your input, but what about your input device? In many audio recording situations, the size of the input jack and type of audio card are not nearly as important as the microphone that you are using. If you have a good microphone and recording settings of at least 16 bit, stereo, 44kHz, then you should achieve an adequate recording. (Keep in mind that the standard for CD audio is 16 bit, 44.1kHz, but DV is 16 bit 48kHz.) To pick a good microphone, you need to consider a few factors.

Power and Pre-Amps

Some microphones, called active microphones, use batteries in their bodies to give them power, other mics require a separate device to provide power, and a third group requires no additional power, only a pre-amp to amplify the mic's signal.

Microphones requiring separate power are known as phantom microphones or condensers. They must be plugged into a port that not only takes in their signal, but also provides power. If the input port of your audio card does not provide phantom power for your microphone, then you must purchase a phantom power box that accepts the microphone input on one side, provides it power, and connects to your recording device with the powered signal on the other side. When you purchase or order your microphone, be sure to identify whether it is phantom or self-powering. Higher quality and expensive microphones commonly require either phantom power or a pre-amp.

Microphones that don't need power may, however, require a pre-amp, which is a small box that acts as a go-between from your microphone to your recording device. The microphone plugs into the pre-amp, which plugs into the recording device. The benefit of having a pre-amp is that it can gain stage, or boost, the incoming signal from the mic to give you a stronger incoming audio level. Some phantom boxes also come with a built-in pre-amp. Using the pre-amp's dial, you can increase or decrease the strength of the signal coming out of the microphone. Conveniently, the 1/8" stereo jack on your default Windows audio card has a built-in pre-amp, making it easy to use basic webcam voice microphones and other basic microphones without having to worry about any additional devices.

Microphone Classifications

The next factor to consider when shopping for a microphone is which type will be best for your projects. Microphones are specified in three groups:

• Dynamic microphones. The type of mics that you typically see on a desk at a press conference or near the drums of a rock concert. Shaped like ice cream cones, they are very durable, are self-powered, and can handle a very high range of noise, from loud crashes to whispers. These mics are usually not too expensive (around $100) and are perfect for the home recording of voiceovers. Dynamic mics that don't require power are commonly referred to as passive.

• Condenser microphones. Typically either phantom or battery-powered microphones. They have a better range and clarity level than dynamic mics; they also respond better to different frequencies. Condenser microphones break down into further categories, but for now it is important simply to know that condenser microphones are useful for recording professional voiceover content or the voice of a singer.

• Ribbon microphones. Very expensive and very delicate microphones that cannot handle high sound pressure levels (loud noises) well. Like dynamic mics, they do not require additional power. Ribbon microphones are perfect for recording ambient noises and natural sounds, because the character of the metallic ribbon's response to sound produces very warm, natural recordings. Related to ribbon microphones are PZMs (pressure zone microphone). Typically flat, plate-like devices, PZMs are omnidirectional microphones that can be placed on a wall to record the sounds and ambient atmosphere of an entire room. If you need to record atmospheres and ambient noises for a film or other project, you could rent a ribbon microphone.

Each type of microphone can either be omni-directional or uni-directional. For omni-directional mics, the field of recording sound comes from all in one focused direction and sounds that do not fall within the pickup pattern are rejected. In other words, the recording comes from one specific direction. Uni-directional microphones vary in their degree of sensitivity much like the angle and diameter of a spotlight (Figure 17.15).

Figure 17.15. Common for film production, 20-degree directional mics (top) are pointed directly at the mouth of a character so as to not pick up other sounds. A 45-degree mic (middle) picks up sounds from a wider range. Omni-directional mics (bottom) are useful for picking up a full range of natural sounds coming from all directions

For example, shotgun microphones are uni-directional microphones that are always pointed toward the mouth of the character who is speaking. On film sets, you see these microphones being held on a long stick (boom) above the actors' heads during filming. The boom operator is the person who gets the microphone close enough to record, but out of the view of what's being filmed. The real benefit of the shotgun mic is that it captures the actor's voice only, while rejecting most of the production sound and noise coming from behind or above.

Depending on your budget and intended use, you can explore a simple dynamic directional mic or a condenser mic for recording live audio.