Hack3.3.Pick the Right Microphone
Hack 3.3. Pick the Right Microphone
Learn everything you need to know to pick the right microphone, or set of microphones, for your podcast. No matter what kind of content your podcast will carry, odds are you'll need a microphone somewhere in the process. Many different microphone types are available, and some are specially tailored for a particular use. Matching the mic to your needs will give you better sonic results, and might even save you some money! If all you want is to get your voice on a podcast, you can use the built-in mic on your computer or webcam, or get an inexpensive USB headset mic [Hack #12] or a basic computer mic with a mini-plug that can jack straight into your computer if it has a micinput. But if you want to get a richer, more professional, more radio-like sound, or if you are recording material out in the field, you'll want a better mic. 3.3.1. Dynamic or CondenserMicrophones come in two types: dynamic and condenser. In general, dynamic mics are more forgiving of rough treatment and do not require external phantom power. Condenser mics break more easily if dropped and require phantom power to operate, which must come from a recorder, a mixer, a preamp, an internal battery, or a separate power source. Condenser mics almost always provide louder output, reducing the amount of gain needed at the often-noisy preamplification stage. And condensers often give a brighter, more detailed sound. Neither type is inherently better than the other is. Very commonly used in radio studios as announcer mics, dynamic mics such as the Electro-Voice RE20, Shure SM7B, and Sennheiser 421 produce very high-quality results. And the Shure SM57 and SM58 are reliable, inexpensive standards. In the field, the overall durability and lack of phantom-power issues make dynamic mics very attractive. Large diaphragm condenser mics, such as the Neumann U 87 or AKG C 414, are standards for voice recording in studios. In recent years, inexpensive versions of this kind of mic have become easy to afford. These large, sensitive mics work best in a quiet, controlled space. People often are confused between phantom power and preamplification. Although many microphone preamps provide phantom power, preamplification and phantom power are separate things. All microphones require a preamp stage to raise levels up to line level, but condenser mics, and some other types, also require a low-level current to charge the mic diaphragm, setting up the electrical differential between the mic's diaphragm and backplate. Most studio mics want to see 48-volt phantom power. Some condenser mics, especially those designed to be used in the field [Hack #69], can accept a battery to provide the phantom power. This eliminates the need for an external box if your recorder or mixer will not provide power, but also adds another battery that can drain at the least opportune moment. If you plan to plug directly into your computer or a small consumer recorder, it's easiest to use a dynamic mic, or a condenser mic that can get phantom power from a battery. If you are plugging into a mixer, a professional recorder, or some other device that provides phantom power, you can use either type of mic. 3.3.2. Pick-up PatternsMics can have various pick-up patterns, meaning the shape ofthe area around the mic where it is most sensitive. Some mics can be switched to change patterns, or you can screw capsules on and off to change the pattern, giving greater flexibility. Of course, these mics are usually more expensive than fixed-pattern mics, so if you're on a tight budget, you might want to choose a fixed-pattern mic that best suits your needs. The most common directional pattern for announcer mics is called cardioid (see Figure 3-5), for its heart-shaped area of maximum sensitivity (mostly out in front of the mic but with a small lobe on either side of the capsule). Sounds to the sides and especially to the rear of the mic are largely rejected or at least reduced; sounds directly in front of the mic are picked up best. Figure 3-5. The cardioid microphone pattern Hypercardioids have an even smaller, more focused pattern. The most directional mic is the shotgun mic, which is designed to highlight a narrow space, often from greater distances. It's important to note that even the most directional mics do not completely reject sound outside of the pick-up pattern. Off-axis sounds are reduced in volume, but they also often acquire a phasey or muffled character, sometimes making extraneous sounds seem rather odd. Sometimes, what's most effective for one purpose, such as reducing feedback on a noisy rock concert stage, is not as pleasing for another, such as an intimate commentary in a quiet room. The next most common pick-up pattern is called omnidirectional (see Figure 3-6), for its ability to pick up sounds in all directions equally. Because of the mic's design, it has less focus on a particular direction, but also, off-axis sounds are picked up more accurately and naturally, lending a more realistic ambience. Some people mistakenly believe that omni mics will pick up close and distant sounds equally, making the background too loud compared to the primary source. But thesemics must still obey the laws of physics, and focus on the subject can be achieved simply by getting the mic in close. In most cases, to get good sound on tape, you must get the microphone close to the source because its sound pressure levels are dropping rapidly as you increase your distance. Figure 3-6. The omnidirectional microphone pattern Omnidirectional mics have the added benefit of being less susceptible to handling noise and more tolerant of wind and plosives (popped p sounds and the like), and they create less "boominess" when close to the source. No mic is completely free from these problems, but omnis show less of this behavior than directional mics. The more directional the mic, the more susceptible it is to handling noise, wind, and plosives, and the more of a boomy proximity effect the mic gets. But the more directional the mic, the less background noise it gets, which can make for a much more pleasing, immediate sound. 3.3.2.1 Microphone diaphragms.Among the varieties of microphones mentioned earlier is yet another distinction based on the size of the diaphragm. Dynamic or condenser, regardless of pattern, can each employ a large or small diaphragm. Large-diaphragm mics are best suited for studio work in controlled environments, where they can be placed on a stand, preferably with a shock mount and a pop filter. The larger, more flexible diaphragm gives a richer, more detailed sound with a higher sensitivity, and so is generally preferable for primary announcing duties. But these large-diaphragm mics are very susceptible to extraneous noise and vibrations, and despite frequent claims by manufacturers of having integral pop filters, they always need additional foam or mesh pop-reduction devices. Many of these mics are meant to be addressed from the side, rather than the end of the mic, and cardioid mics will sound good from only one side. So, try a few positions for you and the mic until you find the perfect angle and distance. Small-diaphragm mics can usually handle louder sources, and counterintuitively, they actually can have a larger frequency range, due primarily to the smaller diaphragm having less mass. Some small-diaphragm mics can work very well as voice mics, but often they sound best when they're not directly in front of the subject, and instead are placed above or to the side so that the person is speaking past the mic, not directly into it. Handheld mics designed for singers can be good for recording the speaking voice as well, although the frequencies are sometimes "hyped" in the bass and treble to sound more vivid, which can be good or bad. Just don't use them like rock singers do, with the mic pressed right against your mouth! Back up about 6 inches and get off to the side, and those singers' mics, such as the Shure SM58, can sound great. Choosing which pattern to use is largely a question of taste and production style. Some producers prefer the open sound of an omni, others the closer, tighter sound of a directional. Some even use short shotgun mics up close for interviews, giving a high degree of rejection of extraneous noise. 3.3.3. LavaliersAvoid the temptation to use lavalier microphones unless absolutely necessary. Clipped to a lapel or hanging around the neck, the lav mic is in a less-than-ideal position for good voice pick-up. Additionally, if the subject is moving around, clothes and cables will likely add unacceptable noise. Lavalier mics are crucial in some circumstances, however: for instance, if the interview is being filmed, or if the subject is too self-conscious when having a mic pointed at him. But every time we do direct A-B tests, a lavalier sounds significantly worse than a well-placed handheld mic. 3.3.4. Choosing the Right MicNo microphone is perfect for all users. When choosing a microphone, you have to decide what is right for you: omni or directional, dynamic or condenser, handheld or lavalier, and mono or stereo. You face a few additional challenges if you are using a small consumer recorder, or are recording directly into a computer's mic input, because the mic input is a high-impedance, 1/8-inch mini connector, and most pro microphones are low impedance with XLR connectors. You'll get better sound quality using a pro mic, even an inexpensive one, than you will by using a consumer mic with a mini connector on it, as long as you've got the right adapters. Get a high-quality converter cable, wired for this purpose, with a 1/8-inch mono connector on the recorder end if you are using a single mono microphone. You can find these on the Web from broadcast supply houses. If you're using a relatively low-output mic, such as a dynamic omni mic, it can be worthwhile to get a cable that adapts from XLR to mini, adjusts the impedance, and shunts the plug-in power. The Shure A96F does all of these things. Louder mics are less likely to need this little boost. For field recording, the most popular mics are omnis, such as the Electro-Voice RE-50 and the beyerdynamic M 58. A popular cardioid mic is the Shure SM58. Shotgun mics by Audio-Technica and Sennheiser are frequent choices. These mics are designed to be plugged into low-impedance XLR mic inputs, but they can work with a consumer recorder that has a mini input, and a good adapter cable. Condenser mics require phantom power. That power can be provided by some recorders [Hack #69], a mixer [Hack #14], an external device, or sometimes an internal battery. Many of the small consumer mini-discs, video cameras, and some other recorders have something called plug-in power, which is similar to phantom power but cannot power professional mics, although it can provide power for electret mics designed to be used with these recorders. In most cases, you will get better sound quality with a handheld microphone. Because you attach lavalier mics to lapels or wear them around your neck, they often pick up clothes rustle. In some circumstances, however, such as an intimate conversation during which an obvious mic would interfere with the feel of the interview, or a subject moving in such a way that keeping him "on-mic" would be impossible, a lav can save the day. If you are going for the up-close, intimate feel that is so prized in audio productions, though, lavs can often disappoint, sounding distant or muddy. If you are recording an intimate monologue or a typical radio-style announcement, your field-recording mics might leave you sounding a little weak or distant. That big, rich sound tends to come from a large-diaphragm mic, addressed from close by, in a quiet room. In a perfect world, you would use a big, expensive mic in a soundproof and acoustically treated booth, but that's not always practical. An inexpensive, large-diaphragm condenser mic, such as the Studio Projects B1 or the Audio-Technica 2020, can get you pretty close to that sound, if you can record in a room with some soft surfaces and not too much computer whirring or other extraneous sounds. 3.3.4.1 Mono or stereo?Stereo sound can add a lot to the vividness of your location recordings, but can be quite distracting during interviews. So, you might want a stereo mic for ambience and demos and a mono mic for interviews. The inexpensive stereo mics that are sold to go with consumer mini-disc recorders can get decent sound, and they can be more than sufficient to get some backgrounds for your piece, but they are not particularly durable, are often made of plastic, and have limited bandwidth, reducing high-frequency detail. The Sony ECM-MS957 and 907 are built to interface with mini-jack mic inputs with plug-in power, and they can sound good. If you want to step up a notch, some good choices are the relatively inexpensive Audio-Technica 822, the Rode NT4, and the Shure VP88. Most conventional interview mics are mono, in that they produce only one channel of sound. Often you connect a cable from that mic to the recorder, which is wired to send that same signal to both the left and right channels of the tape or disc. This is often preferable to hearing the microphone in only one ear while monitoring the recording, but it doesn't make it stereo, since there's just an exact copy of the signal on both channels. It's easy enough to record just one channel and pan it to the center during your mix or to copy one signal to both left and right if that's easier. In fact, when transferring audio to the computer, it will save disk space to record only one channel onto your hard disk if the sound is not stereo. Stereo is most commonly used to describe two tracks of audio, a left channel and a right channel, which are meant to represent a spatial orientation analogous to how our ears hear. You can make a stereo recording with two microphones, or with a stereo mic that has two mic elements in one housing. Depending on the recorder's input, the signals from the two mics or mic elements can be carried on two cables, or on a single cable. Cabling can be very confusing, because the same types of wires and connectors can be used in very different ways. In the analog realm, you usually need one cable for each channel of audio, so connecting most gear will require a cable for the right channel and a cable for the left. RCA cables and 1/4-inch Tip Sleeve cables that have a single ring on the jack carry only one channel of audio. But for the sake of saving space, small, portable recorders, laptops, and a few other devices use stereo inputs or outputs on a single jack. In that case, you can use one cable to transfer stereo audio, as long as it is a three-conductor cable with the correct TRS connectors on the ends. TRS stands for Tip-Ring-Sleeve, referring to the three conductors on the plugs. You'll see two black bands on the plugsone near the tip, another ring about midway downand the long sleeve of the shaft is a conductor as well. One-eighth-inch or "mini" TRS cables are commonly used for connecting the stereo headphone output of a small mini-disc recorder to the stereo mic input on a computer. Some stereo mics use a mini TRS (often just called a "stereo mini") plug to connect to the mic inputs of a mini-disc, a small portable DAT recorder, or a computer. You might need adapter cables to interface a device that uses a stereo input or output with a mixer or audio interface. For instance, to connect a portable mini-disc to an audio interface such as the Digidesign Mbox, you need a cable with a mini TRS on one end and two 1/4-inch cables on the other. Plug the mini TRS into the headphone out of the mini-disc, and the 1/4-inch cables into separate left and right inputs of the interface. Even professional mono mics can use an adapter cable that terminates in a mini TRS plug; in this case, because only one channel of audio is coming from the mic, the cable should be wired to send the audio to both the tip and the ring. 3.3.4.2 Field recording microphones.Table 3-5 lists a variety of field recording microphones. The microphones I've tested are shown in italics. Note that you can find all of these microphones on the Web for 30% to 70% off the prices listed in the table.
3.3.4.3 Studio microphones.Table 3-6 shows a selection of studio microphones. The microphones I've tested are in italics. Note that you can find all of these microphones on the Web for 30% to 70% off the prices listed in the table.
3.3.5. Purchasing MicrophonesAny of the microphones in Table 3-5 and Table 3-6 will serve a podcast very nicely. With this much variability in price, it's difficult to know how much to spend on a microphone. Compounding this problem is the fact that microphones are paired with preamps, and some combinations of the two will work better than others will. So, you might spend a lot of money on a mic and not couple it with the right preamp and get poor sound quality. Here are a few ideas:
3.3.6. See Also
Jeff Towne |
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