Digital Video - March 2008 - (Page 34)

>FYI DYNAMICDUOS Think of those mikes as your backup — good to have, but not your first choice. Microphones are distinguished by how they convert sound waves into electrical energy and their pickup patterns. Although there are a number of ways to convert sounds into electrical impulses, the majority of video productions tend to use only three types of microphones: dynamic, capacitor and electret. All three types of microphones use a moving diaphragm to capture sound, but use different electrical principles for converting the mechanical energy of the diaphragm into an electrical signal. Most handheld microphones are dynamic. They’re popular because they’re relatively inexpensive, rugged and don’t need a power supply or batteries. The downside to dynamic mikes is in how they convert sound to electricity. By using a diaphragm attached to a small coil of wire suspended in a permanent magnetic field, a dynamic mike works like a mini electric generator. The problem is that sound waves need to move both the diaphragm and the coil, which can take away from high-frequency performance and the reproduction of quiet sounds. The capacitor microphone is built around a pair of conducting plates, one fixed and the other acting as a moving diaphragm. As the diaphragm vibrates and the spacing between the plates changes, the capacitance changes. When a fixed electrical charge is applied to the capacitor, an electrical signal is produced that mimics the diaphragm vibration. Because the diaphragm is lightweight, it’s better at picking up high frequency sounds than a dynamic mike. The tradeoff is that capacitor mikes have a built-in preamp to boost the electrical signal, which is why they tend to cost more than dynamic mikes and require power to work. That power typically comes in the form of 48-volt phantom power, which is typically provided by a soundboard and some professional camcorders. There are also some condenser mikes that have their own external power supply, so that the output can be either balanced (XLR) or unbalanced (1⁄4" or 1⁄8"). Electret microphones are a type of capacitor microphone. The difference is that most electret mikes use a diaphragm fixed to permanently charged material and in most cases run from an internal battery. These are typically inexpensive lavaliere mikes with sound quality similar to dynamic mikes. Another type of electret mike is the back electret, where the permanently charged material is fixed to a stationary back plate (not the diaphragm), allowing the use of thinner diaphragms. These mikes can be just as good as capacitor mikes. They will have the battery compartment in either a separate section of 34 dv march 2008 WHAT IS “PHANTOM” POWER? Phantom power got its name because the voltage travels through the standard balanced (XLR) microphone cabling. With no additional power cables needed, the electricity is a phantom in that mike cable. the microphone or a separate attachable capsule. Also, backplate electrets can usually be used with phantom power. PICKUP PATTERNS For videographers, there are four pickup patterns that are the most useful: omnidirectional, cardioid, supercardioid (or hypercardioid) and lobar (or gun). There are a few mikes, such as the AKG C1000S (cardioid/hypercardioid) and Sennheiser K6 (omnidirectional/cardioid/supercardioid/gun), that allow you to change pickup patterns by adding or changing capsule elements. An omnidirectional mike has the most basic pickup pattern and will receive equally from all angles. This can be great if you’re documenting an event and want all the sound you can get, but in Audio-Technica ATH-A55 headphones and a Sony shotgun mike. other instances, it may pick up sounds that you don’t want. Cardioid microphones are unidirectional, meaning they have a tighter pickup pattern than omnidirectional mikes. The name cardioid comes from the heart-shaped pickup pattern. The least sensitive spot of a cardioid mike is behind it, so it’s a good choice when you want to capture what’s in front of and on the sides of the mike. Supercardioid mikes have a tighter pickup pattern than cardioid mikes and will capture less sound from the sides. As a result, they are ideal for handheld use in noisy ambient environments. (Technically, hypercardioid is tighter than supercardioid.) Lobar microphones have the tightest pickup pattern, ignoring even more sounds from the side than supercardioid (but not all of the sounds). These are also known as shotgun mikes, used to capture sounds from directly in front of the pickup element. More than half of what you hear in television and film comes from shotgun mikes because they allow fuller, warmer sound by including a nice balance of ambient sound. DV Michael Silbergleid is the president of The SilverKnight Group, a technology marketing communications company. Contact him at msilbergleid@silverknight.com. www.dv.com http://www.dv.com

Table of Contents Feed for the Digital Edition of Digital Video - March 2008

Digital Video - March 2008 Contents DV Update Q&A Fest Circuit Instant Expert LP-Micro Light Fusion F2 Drive PPFP-3N Bag Ego Digital Imaging Light KE-79CC Boom & Fuzzy Close-Up: Honoring George Spiro Dibie, ASC Food Fight Key Thoughts on Chroma key DV101 Dynamic Duos First Look: A Big Serve Cameras & Courtrooms Ad Index Production Diary

Digital Video - March 2008

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