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The External Mike - The right tool for the right job
To drive a nail, you need a hammer.
To change a flat, you need a lug wrench.
To make good video, you need an external mike.
What? You've never thought of an external mike as an essential tool for making video? It truly is, if you're serious about turning out videos that sound as good as they look.
Most videographers keep plugging away with their camcorder's built-in mike for a handful of seemingly good reasons:
- They wouldn't know which mike to buy
- They can't afford an external mike
- Using an external mike is too much hassle
- External mikes don't make that big of a difference
In the next few pages, we're going to shoot big holes in each
of these four misconceptions. External mikes aren't confusing,
expensive, hard to deal with or a waste of money. They're the
right tool for the job--if the job at hand is making good video.
The External Difference
Your camcorder's mike does a fine job picking up the general wash
of sound that rolls over your camcorder as you shoot. What it
doesn't do well is distinguish between one sound (your subject's
voice, for example) and the competing sounds all around it.
It's not that your camcorder's built-in mike is bad by design--the fidelity of most camcorder mikes is quite good. The real problem lies in its location. Because it's permanently attached to your camcorder, the mike can never be any closer to your subject than the camcorder itself. The distance you shoot video from, however, is rarely the best distance for recording clean audio.
The key to good audio is getting a mike very close to your subject. Your camcorder's lens will zoom in on a subject, making it seem closer than it really is. However, due to the physics of sound, there's no way to be this selective with a mike. Even "zoom" mikes can't focus in tightly on one sound. For a comparison between the pickup patterns of a "zoom" mike and a zoom lens, see figure 1.
Shotgun mikes are much more directional than most built-in mikes,
and will work well in some shooting situations. Even with a shotgun
mike, though, the rule of thumb for good audio still applies--get
close.
Bite-size Pieces
At first glance, the world of external mikes is a confusing one.
There are countless styles and makes to choose from, and it can
be tough to distinguish one type of mike from the next. Once you
realize that external mikes fall into several smaller categories--bite-sized
pieces, if you will--things get much easier.
A given mike will belong to a specific category in three different areas: element type, pickup pattern and physical type. Sometimes, one category will imply another (a given physical type could consistently have the same pickup pattern, for example). Other times, it's a free-for-all.
One way we categorize external mikes is by how they convert sound energy into an electric signal. The part of the mike that actually performs this conversion is the element. The two types of element used in the vast majority of external mikes are condenser and dynamic.
Condenser elements offer the highest fidelity available, but have a slight drawback. Because the signal from the mike element is so tiny, condenser mikes must have a built-in preamp to boost the signal. This preamp requires power, either from a built-in battery or phantom power sent down the mike cable itself. Some mikes will work only with a battery installed, others will work only with camcorders or mixers capable of supplying phantom power. Sony Plug-in Power mikes, for example, only work with camcorders that have a tiny DC (direct current) output for the mike.
Dynamic mikes offer fidelity almost on par with condensers. As a plus, dynamics put out a strong enough signal that they don't need a built-in preamp. This means dynamic mikes require no batteries (which can go dead at the most inopportune times) and will work with virtually any mixer, camcorder or audio recorder. Dynamic mikes also tend to be more rugged than condenser mikes.
Two other element types deserve mention, though they're unusual
in mikes used for videography. The first is a ribbon element,
which functions much like a dynamic element. Ribbon mikes sound
great, require no power source, but tend to be fragile and somewhat
pricey. Boundary-plate mikes often look somewhat like a flyswatter,
with a thin, flat base. These condenser-type mikes sound good,
but require a power source of some kind. Boundary mikes usually
offer a very broad pickup pattern, which doesn't make them selective
enough for most video applications.
This is a Pickup
The second way of categorizing mikes is by how they discriminate
(or if they do at all) between sounds coming from different directions.
We call this the mike's pickup pattern. Mikes that pick
up sound equally from all directions are omnidirectional.
A mike that is more sensitive to sounds emanating from directly
in front of it is a directional mike. Directional mikes
break down further into three or four categories, depending on
how directional they are.
The basic directional pattern is the cardioid pattern, so named because it looks much like a heart. Mikes that are even more directional than the cardioid are called supercardioid and hypercardioid. Each of these focus the pickup area in front of the mike a little tighter. It's worth noting that supercardioid and hypercardioid are also more sensitive to sounds coming from directly behind them than the cardioid is. To the sides of the mike, however, these patterns offer better rejection.
Most directional of all is the shotgun mike, which has an even tighter pickup directly in front of the mike. There's no real name for this pickup pattern, but we often call it a "shotgun" pattern after the mike type that offers it.
The main goal of the directional mike is to isolate a specific sound from the ambient sound, reverb and noise of a given location. To put some numbers to the theory, imagine you're recording a person speaking in a room. At a certain distance--three feet, example--an omnidirectional mike is going to give you a certain mix of direct and ambient sounds. In an average living room, this would most likely be a pleasing blend of the voice and some ambience and reverb from the room.
A cardioid mike will give you the same ratio of direct and reflected
sounds, but at a distance 1.7 times greater (about five feet away).
Supercardioid and hypercardioid patterns will give you the same
blend from about twice the distance (roughly six feet). A shotgun
mike may let you move three times the distance away (about nine
feet) without adverse effects.
Get Physical
In our discussion of mike types, we've left the best and most
descriptive category for last--physical type. Physical type describes
the main functional characteristic of the mike, usually implying
an application. This is the category that other videographers,
brochures and salesfolk often start with when describing a microphone.
"It's a lavalier," they'll say, or "it's a handheld
mike." Physical type is also where we'll begin exploring
specific microphone models.
When it comes to physical type, external mikes fall into three
main categories: handheld, lavalier and shotgun. Each has its
own applications, and videographers often have at least one mike
of each type in their arsenal.
Handheld Mikes
The term "handheld" pretty much sums up the application
of our first mike type. These mikes tend to be very versatile,
working well for recording interviews, narration and even musical
instruments. Because subjects often hold them, handheld mikes
usually have some sort of internal shock mounting to minimize
handling noise. Many handheld mikes also forego a flat frequency
response for the sake of added speech clarity, adding a boost
to the upper-midrange response. This makes these mikes sound great
up close to a talking subject, but can make them sound "thin"
when used at a distance of more than a foot or two.
Handheld mikes are available in all possible pickup patterns. Omnidirectional handhelds offer a very natural sound for video and ENG (electronic news gathering) applications. Cardioid and hypercardioid mikes offer better noise rejection. You can also find handheld mikes with either dynamic or condenser elements, in wireless or wired versions.
The Audix OM-3xb ($199) handheld dynamic microphone has a cardioid pickup pattern and ultra-low mass diaphragm for clear sound. Designed for "on-the-street" interviews, the Shure VP64 ($135) is an omnidirectional handheld dynamic mike with effective shock isolation and high signal output. Electro-Voice's 635L handheld omnidirectional dynamic mike ($198) offers an extra-long handle for better reach in interview situations, and is available in both fawn beige and black.
The M01, M02 and M03 handheld dynamic mikes from Beyerdynamic
($99, $119, $129) offer supercardioid pickup patterns and internal
rubber suspension for lower handling noise. Beyerdynamic's M58
handheld dynamic mike ($259) offers an omnidirectional pattern,
extra-long handle and internal shock-mount system.
Shotgun and Camcorder-mounted Mikes
Shotgun mikes, whose long tube looks something like that of a
shotgun, are generally the most directional mikes available. Because
of the technology used to cancel out sound coming from behind,
you can often tell the tightness of a given shotgun mike's pattern
by looking at the length of its tube. Longer "interference
tubes" (on the order of 12-18 inches) make for a tighter
pickup pattern; shorter tubes rarely offer a pattern much tighter
than a standard hypercardioid mike.
A shotgun mike will usually outperform a built-in mike when mounted right on the camcorder. Better still is to mount the mike on a long pole called a boom. A boom allows the mike operator to position the mike just outside the camcorder's view, but still quite close to your talent. This short pickup distance (usually just a few feet) coupled with the tight pattern of the mike makes boom-mounted shotgun mikes almost as effective as the lavalier for blocking out unwanted sounds.
The Sony ECM-Z157 ($90) is a camcorder-mounted, battery-powered shotgun mike that offers omnidirectional, cardioid and supercardioid pickup patterns. Sennheiser's MKE300 shotgun mike ($249) offers a supercardioid pickup pattern, minijack output, suspension mount for resistance to vibration and built-in battery.
The AT835b from Audio-Technica ($329) is a battery- or phantom-powered shotgun mike suitable for boom or camcorder-mounted applications. Nady's VCM-100 directional shotgun mike ($65) works well for boom or on-camcorder applications. The Azden ECZ-990 shotgun mike ($100) is a compact, camcorder-mounted microphone with tight pickup pattern.
Lavalier Mikes
Lavalier mikes are tiny by design, making them inconspicuous enough
to attach right to your on-screen talent. Because the lavalier
mike is so close to the speaker's mouth, his or her voice comes
across much louder than the competing noise. Even when using an
omnidirectional lavalier mike, sound pickup is clean and clear.
Because it's tricky to make miniature dynamic elements, most lavalier mikes are of condenser design. This means they require either a built-in battery or power from another source. Many lavaliers have a battery housing mounted part way down their cable; others draw power directly from a wireless transmitter.
The Crown GLM-100 miniature lavalier is an omnidirectional condenser mike available with output electronics for cabled use or without electronics for wireless applications ($209 and $105, respectively). One of the few dynamic lavalier mikes available, Shure's SM11 ($117) is an omnidirectional unit which offers the benefit of needing no power supply or battery.
Wireless Mikes
Though not technically a mike "type," wireless mikes
deserve their own discussion. Wireless mikes offer the utmost
in freedom, putting an end to tangled cables and limited shooting
distances. Most good wireless transmitters will give you reliable
sound from 100 feet away or more, depending on conditions.
Wireless mikes most often come in two different styles: handheld and lavalier. Wireless handheld mikes are very convenient for interviews or commentary, especially where mobility is an issue. The transmitter is part of the handheld mike itself, making the whole mike assembly just slightly larger than a wired version.
Wireless lavalier mikes offer that crisp, up-close "lav" sound without the nasty cables. Wireless lavs are almost always condenser mikes, because there's a handy power supply at the transmitter end of the cable. Wireless lav transmitters are usually belt packs about the size of a deck of playing cards, using a 9-volt battery for power.
Wireless receivers usually mount directly to the camcorder, and also rely on a 9-volt battery for power. A miniplug cable carries the wireless mike signal from the receiver to the camcorder.
Sony's affordable WCS-990 wireless mike system ($150) offers a lavalier mike, two transmission channels, an earphone monitor and a transmission range of up to 100 feet. Azden's WR22-Pro receiver ($280) is a two-channel, camera-mounted unit that works with any Azden wireless microphone.
Nady's affordable 151 VR VHF wireless mike system ($230 with handheld mike, $280 with lavalier) offers 250-foot range, noise reduction and minijack audio output. The Nady 551 VR ($850) offers two switchable VHF frequencies and surface-mount technology for reduced size and weight.
Plugging it In
Interfacing an external mike to your camcorder is rarely as simple
as just plugging it in. Many professional mikes use a low-impedance,
balanced signal on a three-pin XLR connector. This type
of signal stays crisp and clear over long cable runs, and actually
cancels out any noise picked up in the cable. Most consumer camcorders
have unbalanced, high-impedance inputs on minijack connectors--that's
strike one, two and three for the humble camcorder. Thankfully,
the solution is as simple as converting the professional mike
signal with an impedance-matching transformer. Available for less
than $50 from such manufacturers as Shure, Audio-Technica and
Radio Shack, this converter attaches between the mike cable and
the camcorder input.
The last snag you may need to work around when using professional mikes is that of phantom power. Some pro condenser mikes work with phantom power only, and no consumer camcorder supplies phantom power down the mike cable. The solution? An external phantom power box. This box plugs into an outlet and supplies power to the condenser mike, intercepting the mike cable between camcorder and microphone. Whirlwind (888-733-4396) even makes a phantom power supply that runs off a pair of 9-volt batteries.
Without a doubt, using an external mike with your camcorder is the best thing your can do for your audio. The clarity and power of your soundtracks will improve, and you'll become a better videographer.
That's what happens when you use the right tool for the job.
Contributing editor Loren Alldrin is a freelance video and music producer.
Glossary
- Zoom Mike
- A combination stereo mike/mono mike system on
some camcorders that uses the stereo mike signal when the lens
is in the wide-angle setting, and the mono mike signal when the
lens is in the telephoto position.
- Element
- The part of the microphone that converts sound
waves into an electrical signal.
- Condenser Element
- A small microphone element consisting of a diaphragm attached to a condenser and a preamp that requires power from a battery or from the camcorder or mixer to which it is attached.
-
- Preamp
- A low-level amplifier that boosts the very weak
signal produced by a condenser mike to a usable level.
- Phantom Power
- Power supplied to a condenser element by
a camcorder or mixer.
- Dynamic Element
- A microphone element consisting of a diaphragm
attached to a freely moving wire coil surrounding a magnet. This
arrangement is mechanically rugged and produces a relatively strong
electrical signal.
- Pickup Pattern
- A graphical representation of the directions
from which a microphone will pick up sound.
- Omnidirectional
- A microphone that picks up sounds from
all directions.
- Directional
- A microphone pickup pattern that is not omnidirectional.
- Cardioid
- A somewhat directional pickup pattern that resembles
a heart.
- Supercardioid
- A pickup pattern that is similar to the cardioid
pattern, but more directional.
- Hypercardioid
- A very directional pickup pattern.
- Shotgun Mike
- A long, tubular microphone that has a highly
directional pickup pattern. See supercardioid and hypercardioid.
- Boom
- A long pole used to carry and position a shotgun mike.
- A long pole used to carry and position a shotgun mike.
- Handheld Mike
- A mike with a handle that can be placed in
the hand or clamped onto a mike stand.
- Lavalier Mike
- A small mike, usually having a condenser
element, that is attached to the speaker's lapel or otherwise
suspended below the speaker's mouth.
- Impedance
- An electrical characteristic of microphones and
audio circuits that must match in order for the two to work properly
together. High-impedance mikes must be used with high-impedance
equipment, and low-impedance mikes must be used with low-impedance
equipment.
- Balanced Signal
- An audio signal carried by a three-conductor
cable.
- Unbalanced Signal
- An audio signal carried by a two-conductor cable.
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