Sound on Site
Posted Aug 5, 2004

When you're doing professional shoots, you've got two alternatives for capturing higher-quality audio: get really, really close to your subject, or get an external microphone. Assuming that close proximity is not always an option, with all the mics, connections, and strategies available, what do you need to know to do on-site sound right?

It generally only takes a video shoot or two before you realize that the weakest link on your camcorder is the microphone. Don't worry: It's not you, or really your camcorder for that matter, just the simple fact of life that all onboard microphones are lousy.

This leaves you with two alternatives for capturing higher-quality audio: get really, really close to your subject, or use an external microphone. Assuming that close proximity is not always an option, you'll almost certainly end up going with the latter approach, which is also the more complicated. What do you need to know to do on-site sound right?

We'll start with a brief inventory of your camcorder, which will tell us the type of microphones you can connect to and the equipment you'll need to do so. Then we'll survey the most popular types of microphones and their uses. We'll also run through several common shooting scenarios with specific recommendations for microphone setup.

Note that there are myriad options for working around your camcorder's microphone. In general, I looked at options that were the least expensive, could be operated by the camera person and easily carried with, or attached to, the camera. If you're permanently mic'ing up a room, you should consider a different range of options. But if you're assembling a kit you can afford, take on the road at a moment's notice, and adapt to your next shooting environment, you've come to the right place.

BeachTek, Shure, and Sony provided most of the equipment we tested in this article, which is why their names keep popping up in the recommended equipment list. While they're certainly not the only equipment suppliers out there, we're more comfortable recommending equipment that we've used in the testing described below and several other shoots than passing judgments on microphones sight unseen—or sound unheard, if you will.

Connection Options
There are two ways to connect external microphones to camcorders, though not all camcorders offer either or both options. First, of course, is your microphone port, which comes in two general categories. One is an XLR connector, which is typically available only on high-end prosumer and professional camcorders. The other is the more typical 3.5mm stereo connector (also called a 1/8" connector), which is found on most consumer camcorders.

My Sony DCR-VX2000 camcorder offers both MIC and LINE input, while the vast majority of consumer cameras offer only MIC input. Microphone-level input is the output from the inexpensive, primarily unpowered microphones like those you may have used to record audio to your computer. They're inexpensive, and push out a very weak signal, like a few ten-thousandths of a volt. In contrast, LINE power is produced by a powered sound system like your stereo or a professional sound system. The signal is much, much stronger.

If your camcorder has a MIC input (which it probably does), it should work well with many of the microphones discussed in this article. However, if you ever try to connect your camera to a professional sound system, like that used at a speech or conference, you'll need to reduce the LINE output to MIC level (more on this in the scenarios below). Otherwise, the signal will be too strong for your camera and will produce distortion and possibly damage your camera.

The Sony camcorder, not atypically, also supplies plug-in power to power certain microphones. Specifically, lavaliere and boundary microphones use "condenser" pick-ups to acquire and convert sound to electrical signals. Unlike dynamic microphones, which are driven by magnets and sound waves, condenser microphones need electrical power to produce a signal.

Connect a condenser-type microphone to a camcorder without plug-in power (also called "phantom" power), and you won't get a signal. There are other alternatives for powering these types of microphones, but before buying, it pays to determine whether your camcorder has plug-in power or not. Generally, if it doesn't say so on the microphone port, it doesn't, but check your camera's documentation to be sure.

You can also attach a microphone to a camera if it has an intelligent accessory shoe. An accessory shoe is a bracket that sits atop the camera for holding accessories like lights and microphones. Not all cameras have accessory shoes, and not all accessory shoes are intelligent, meaning that they can provide power, control, or both to installed peripherals.

In Figure 1(, the camera on the left has an accessory shoe, but it's not intelligent, just plain metal on metal. It can certainly hold a camera or light, but it can't send power to the unit, or, more importantly, accept the audio back into the camera and actually use the microphone.

On the right, you can see the metal connectors beneath the covering I've pulled back, which indicates that this accessory shoe is intelligent and can power and communicate to a microphone and flash attachment.

Typically, if the accessory shoe is intelligent, the camera vendor will offer at least one optional microphone, but check your camera vendor to be sure. When available, these microphones are easy to install and use, relatively inexpensive, and can noticeably boost sound quality over that of the embedded microphone.

Types of Microphone
Figure 2 ( shows a good cross section of the types of microphones you should be considering for your shoots. Let's briefly identify them, and then cover the three characteristics of microphones you need to learn before buying.

On the bottom is a handheld microphone, the Shure SM63 ($198 list) like those frequently seen on game shows and news broadcasts. As the name suggests, it's meant to be held in your hand during operation.

When you can use a handheld microphone, it's almost always the best alternative, with a great blend of quality and ease of use. It works well in many one or two-person shoots, or when one interviewer is talking to multiple interviewees. You can also attach them to stands for hands-free operation in speeches, concerts, and conferences.

The Shure EZB/O ($188 list) shown in Figure 2 is a boundary or surface-mount microphone. These microphones are designed to be attached to desks or stage floors to pick up sound from multiple speakers and are typically used in conference rooms and theaters.

The two lavaliere microphones shown in Figure 2 are each designed to be attached to an individual, and used hands-free. The Shure SM 11 Lavaliere ($175 list) is a "wired" lavaliere connected to the camera via cable, while the Sony Lavaliere is part of the Sony WCS-999 wireless microphone system ($149.99 list) that sends the sound over a wireless signal to a receiver mounted on the camera. Lavalieres are excellent alternatives when you have one or two individuals speaking, offering excellent quality and unobtrusive, hands-free operation. However, they're tough to transfer smoothly from person to person during the shoot like a handheld. In addition, because they are smaller, lavalieres are less robust than handheld microphones, so typically don't last as long.

Two microphones shown in Figure 2 that are mounted on a camera's accessory shoe are the Sony ECM-HS1 ($69.99), which connects via an intelligent accessory shoe, and beneath it is the Sony ECM-Z27C ($149.99 list), which connects via the attached cable with a 3.5mm adapter.

While the HS1 can only work on Sony camcorders with intelligent accessory shoes, the Z37C can work with any camcorder that has an accessory shoe and a microphone port. If the camera's microphone port doesn't supply plug-in power, a small battery can power the Z37C.

These two Sony microphones share several characteristics. First, they are shotgun mics designed primarily to pick up sound from directly in front of the camera and eliminate sound from the sides and behind the microphone. In addition, both are monaural mics which pick up only one channel, not stereo mics like most others shown in Figure 2.

In addition to shotgun mode, you can also switch the HS1 into zoom mode, where the pattern of sound picked up by the microphone mimics the current view of the camera's zoom lens. When the zoom lens is pulled completely back into a wide angle view, say to show an entire stage, the sound pickup pattern is also very wide. When the lens is zoomed in telephoto mode to focus on a single performer, the microphone pattern is similarly focused, eliminating all sound except that directly in front of the camera.

As we'll see, shotgun microphones produce better sound than most camcorder microphones, but are inferior to handheld or lavaliere microphones. While generally more flexible and easier to use than the handheld or lavaliere, if quality is your primary goal, shotguns aren't your best alternative.

The Three Questions
This leads us to the three issues you need to address before buying a microphone. Note that you have to ask the same questions whether the microphone is wired or wireless, since the issues are identical.

First is the pickup pattern, or directionality, of the microphone, which defines which sounds the microphone picks up and which it ignores. At one extreme are the "omni-directional" microphones used in your camcorder that pick up sound equally from all sides of the camcorder. At the other extreme are "uni-directional" microphones that pick up sound from a single direction and shut out all other noises.

For some microphones, like the shotguns we've been discussing, the pickup pattern is obvious. Shotgun microphones are designed to ignore ambient sound and are extremely unidirectional. In specification sheets for shotgun microphones, you'll frequently see terms like cardioid, super-cardioid, or even hyper-cardioid pickup patterns, which designate an increasing exclusion of ambient sound to focus more completely on sound that's directly in front of the microphone.

Most other microphones come in either omni-directional or cardioid patterns, and you need to be careful to get the right microphone for the intended use. For example, if you're buying a boundary microphone for use on a lectern where you just want the speaker's voice picked up, a cardioid pattern is the obvious choice. However, if you're buying a boundary microphone for a conference room where all participants must be heard, an omni-directional microphone is a better choice.

It's also critical to know the pickup pattern when using the microphone. For example, if you're using a hyper-cardioid shotgun microphone to pick up a group discussion, you probably won't capture speakers at the periphery of the group. Similarly, a handheld microphone with a cardioid pattern will minimize sounds not emanating from directly in front of the top of the microphone.

The next key issue is whether or not the microphone requires power. As we discussed previously, if the microphone requires power, and your camcorder's microphone doesn't offer plug-in power, you'll have to figure out another way to power the microphone.

Most microphones that need power simply list "Phantom Power Requirements" or something similar on the specification sheet. If not, note that all condenser-type microphones will need power, either from the camcorder or battery. In contrast, dynamic microphones do not need power and can run even if your camcorder doesn't offer plug-in power, assuming you can plug it into your camera, of course. Which leads to our next essential microphone fact, which is connector type.

Virtually all professional microphones connect via what's called an "XLRM" connector, or XLR male connector. This means that the three XLR pins are sticking out of the connector and that your cable will need a female connector to attach to the microphone. Birds and bees at eleven.

XLR is the favored technology because it is "balanced," which means that cables can run long distances without picking up noise for electrical wires and other sources. In contrast, unbalanced cables, like those typically terminated with 3.5mm jacks, pick up noise quite easily, especially as cable lengths grow longer.

For this reason, other than shotgun microphones that mount directly on your camcorder, you'll very rarely see microphones that connect via 3.5mm plugs. The primary exceptions are wireless microphones like the Sony WCS-999 in Figure 2, which uses a 3.5mm jack to connect to your camcorder. However, since the receiver mounts on your camcorder, the distance traveled over the unbalanced wiring is quite short.

Square Peg into a Round Hole
So, if you want to use a high-end microphone with your camcorder and you don't have an XLR jack, you'll have to find a way to convert from the XLR cable to the 3.5mm connector on your camera. We explored two alternatives.

The first was a "line matching transformer" from RadioShack, specifically the A3F XLR Jack-to-1/4" Plug Adapter/ Transformer. Since this product output to a 1/4" plug, I added a 1/4"-to-3.5mm converter, officially the 274-875A connector, to connect to my camcorder. Total cost was under $20, besides the XLR cable. This rig is shown in Figure 3(

In my lab setting, this setup generally worked well, though it converts the stereo signal from the microphone to monaural, and doesn't supply the plug-in power required for many microphones. Ergonomically, however, it's clearly not a field solution, since one inadvertent bump would probably rip my camera into multiple pieces.

If I used the line matching transformer route in the future, I would choose the Shure A96F transformer, which inputs XLR and outputs 3.5mm, with a flexible cable that avoids the right angle attachment shown in Figure 3. Mail order price for the A96F is around $40.

The other alternative we explored is the BeachTek DXA-8 Ultimate Adapter, which lists at $399 but can be found for a few dollars less via mail order. Figure 4 shows the two faces of the product, back and front, which screws into the tripod mount beneath your camcorder, with a similar mount on its bottom so you can continue to use a tripod.

On top, the unit has three connectors, two for XLR cables and one for an unbalanced 3.5mm connector. The output is a 3.5mm connector with microphone power, so you can plug it into any camcorder with a microphone jack.

The twin XLR connectors mean you can use the DXA-8 to mix together two microphone signals, controlling respective volume with the two volume dials shown on the bottom of Figure 4( In contrast with the line matching transformer approach, the DXA-8 captures stereo, not monaural output.

The 48V switch to the right of both volume controls means that the DXA-8, which is powered by a 9-volt battery, can supply phantom power to condenser microphones. In addition, the LMT buttons engage a "limiter" function that prevents distortion from hot inputs, a critical feature when accepting LINE-level input from a sound system. The unit also has preamplifiers that boost the low signal from microphones, which can eliminate hiss.

After using the different approaches to converting XLR input, I liked the BeachTek under-the-camera approach much better. If you don't need all the functionality of the DXA-8, consider the DXA-2, which sells for around $125 and provides one XLR port and one unbalanced 3.5mm input, with volume control but no phantom power or limiters. I would definitely buy this over the RadioShack or even Shure A96F approach.

Sound Quality
So those are the microphones and the ways they connect. But how do they perform?

To test performance, we used a high-quality, digitized recording of a woman speaking, played back over computer speakers at a standardized volume. To create ambient sound, we left all office equipment running, which created a distinct hum of background noise.

We set up the VX2000 approximately ten feet away from the speakers, and then recorded the audio using all the microphones shown in Figure 2. During each recording, we used the VX2000's manual gain controls to boost the audio to an acceptable level. For this reason, while you'll notice some minor volume differences in the waveforms you're about to review, the most significant differences will be in the detail captured by the microphone and the amount of noise in the signal.

Let's start by looking at the difference between the best and the worst, shown in Figure 5(, which contains waveforms produced by the camcorder microphone and the Shure lavaliere microphone. You'll notice that the waveform on the bottom shows higher peaks and valleys, indicating higher volume. You'll also notice that when there was no speech, the line of noise produced by the camcorder was noticeably thicker, indicating more ambient noise.

Most striking, however, is the detail missed by the camcorder. As indicated in the picture, the woman speaking is saying the word "tutorial," and there are noticeable peaks at the "t"s and "i" in "tutorial" with the Shure lavaliere. These peaks are not present in the camcorder mic's waveform, indicating the speech was much more muffled and harder to understand. If you listened to the results, you would find the Shure lavaliere audio clear, crisp, and natural, while the camcorder audio sounded tinny, and almost like it was shot in a barrel or other close quarters.

Overall, the results produced by the Sony Wireless Lavaliere system and the three Shure wired microphones were very similar and clearly superior to that produced by the two shotgun microphones. These findings are illustrated in Figure 6(

Again, the Shure solution produced higher volume, a crisper signal, and slightly less noise. Overall, while the ECM-HS1 and ECM-Z73C produced better audio than the camcorder microphone, the difference was much less striking than that produced by the microphones used closer to the source.

Don't take this as a sweeping indictment of shotgun microphones. Both the Sony models are relatively inexpensive and rather small, and Shure and other vendors offer larger, more sensitive models that would likely produce better results. In the price range we surveyed in this review, however, you'll produce the best results if you can mike up the sound source.

These conclusions noted, we turned our attention to the difference in quality produced by connecting through the RadioShack line matching transformer and the recorded output from the BeachTek DXA-8. This is shown in Figure 7(

As you can see, the RadioShack produces a monaural signal, which is why there is only one waveform. Detail is quite good, and the signal is slightly less noisy than the bottom signal, which was produced through the BeachTek unit.

However, the noise is less because the signal is lower than the BeachTek unit, which sounds much more vibrant. In addition, the BeachTek signal is much more nuanced than the RadioShack signal, which sounds a bit flat. Overall, most listeners would clearly find the BeachTek audio the more pleasing of the two.

On-Site Sound Scenarios

Let's look at several common scenarios and discuss the different microphone alternatives. I'll assume that your camera has a single 3.5mm microphone connector that accepts microphone-level audio.

Scenario 1

Wedding requirements vary dramatically over the course of the wedding, and it's very difficult to propose one setup that works in all instances. At the very least, you'll need a microphone on the groom-either a wireless microphone like the WCS-999 or a MiniDisc or DAT tape recorder-and a shotgun microphone for the reception (or cabled or wireless handheld).

Since you may need to use the shotgun and lavaliere microphone simultaneously, you'll need a mixer like the DXA-8. Since the DXA-8 offers only one 3.5mm input, which you'll use for the wireless microphone, you'll also need a shotgun microphone with XLR output, which neither of the Sony units offers.

Scenario 2
Single person talking (CEO broadcast, customer testimonial)

Sony WCS-999 Wireless Microphone system ($149.99 list). This system is easy to operate and connect to your camcorder, produces high-quality audio, and can move around with the speaker. Total cost: $149.99.

Scenario 3
Two people talking on camera (interview, training)

Rig 1: Shure SM63 Handheld Microphone ($198 list), Shure AF96F ($40), 15-foot XLR cable ($14.99, RadioShack). Speakers share the handheld microphone; functional, good-quality audio, but inelegant. Total cost (approximate): $260.

Rig 2: Shure EZB/O Boundary Microphone ($188 list), Shure AF96F ($40), 15-foot XLR cable ($14.99, RadioShack). Hands-free operation; functional, good-quality audio. Total Cost (approximate): $250. Caveats: Room must be otherwise quiet, and the boundary microphones work best when placed on a raised desk or table.

Rig 3: Two Shure SM11 Lavaliere Microphones ($350 for both), two 15-foot XLR cables ($30 total), BeachTek DXA-8 ($399). Killer system with great quality and flexibility. Total cost (approximate): $800.

Scenario 4
Connecting to a Sound System

If you're shooting a concert or conference, you'll get the best sound by connecting to the output of the on-site production sound system. In most instances, you'll have to solve at least two issues: the physical connection from the soundboard to the camcorder, and dropping the line-level output to microphone-level input for your camera (assuming that it doesn't accept line-level input).

Depending upon the soundboard, the outputs can be anything from RCA connectors like those on your stereo, to 1/4" jacks to XLR connectors, and you should be prepared for all three possibilities. We assumed XLR output for our suggested systems.

Rig 1: The Shure A15LA Line Input Adapter ($42 retail) to drop the LINE-level output to microphone input and the Shure AF96F ($40) to convert from XLR to 3.5mm. Total cost: under $100. Caveat: You have no ability to adjust the sound coming from the sound system, which may still be pretty hot.

Rig 2: BeachTek DXA-8 ($399). This unit can perform both conversions (XLR to 3.5mm and line to microphone) while offering limiters that help ensure distortion-free audio, plus a ton of utility in other shooting environments.

Noise Reduction Software

When we created our test setup for this project, we deliberately left our computers, routers, printers, and monitors running, producing a consistent din of ambient noise. Our reasoning was pretty obvious: How can you possibly test a shotgun microphone's ability to ignore ambient sound without lots of ambient sound? In addition, since few weddings, interviews, or other videos are shot in sound booths, the noise also provided a lovely dose of reality.

Of course, once we heard the background noise present in even our highest-quality recordings, our thoughts quickly turned to noise reduction software, which works best with regular, consistent background noise like machine hum or tape rumble, as opposed to irregular noises like crowds cheering or traffic noises. We surveyed our labs and some recent press releases, and assembled three products.

First on our list was Sony Pictures' vaunted Noise Reduction filter for Sound Forge, which costs $279.97, but requires Sound Forge ($399) or another DirectX-compatible audio editor to run.

Next was BIAS's newly released SoundSoap Pro for Windows ($599 retail), which functions as a DirectX plug-in that we ran within Sound Forge. Third was the noise reduction capability that comes with Adobe Audition, a complete audio editor that retails for $299, though it's much cheaper in several Adobe bundles.

Note that true noise reduction filters work differently from inexpensive functions typically called noise gates. The machine hum from my office equipment was most noticeable during the brief periods between spoken words in the original recordings, though you can also hear it throughout the recording. Noise gates work by setting thresholds for noise. When the audio exceeds the threshold, the noise gate filter assumes it's audio that's supposed to be heard and leaves it alone. When the volume goes under the threshold, it assumes the audio is noise, and simply eliminates it, reducing its volume to zero.

When the speaker paused for breath in our test recording, a noise gate would reduce the volume to zero, eliminating the hum during the otherwise silent period. However, noise gates do nothing to reduce the audible hum while she's speaking. This produces a noticeably artificial effect, since you can hear the hum when she's speaking, but not when she pauses.

In contrast, all three noise reduction technologies cited here try to identify the background noise and eliminate it throughout the entire recording. You start by selecting an otherwise blank stretch in the audio file that's devoid of speech, music, or other audio that's supposed to be there, and contains only the background hum. Then you tell the noise reduction filter to capture a noise print or noise profile of that hum, and eliminate it from the entire audio file.

We tested noise reduction utilities from Sound Forge, SoundSoap, and Audition on three audio files. We highlighted the same segment in the three original files to identify the noise print and then ran each filter using the default settings.

Two of the audio samples were from this project, one the low-quality audio recorded with the embedded microphone on the Sony camcorder and the other the excellent audio captured with the Shure handheld microphone. We also tested an audio file recorded from a cassette player which will be integrated into a DVD memorializing a recent awards ceremony for the Stoneman family here in Galax.

On the high-quality recording, all three technologies virtually eliminated the machine noise, making it sound like it was recorded in a sound studio. The Shure microphone produced a great original signal, and all three filters made it sound positively pristine.

The results with the lower-quality recording were less encouraging; basically, you can't turn a sow's ear into a silk purse, no matter how good your software is. Though all three programs removed most of the background noise, the detail that wasn't captured by the camcorder's microphone was not magically restored. While the recording sounded better, the improvement was incremental, not exponential. The lesson is clear: get a good microphone setup and don't expect to compensate for onsite recording deficiencies in post.

The results from the cassette tape were simply fantastic, with all three products dramatically reducing tape hiss and rumble. If you're doing this type of conversion, noise reduction technology should be in your budget.

Which product performed best? Very tough call and my instincts are to be politically correct on this one and say they were all equal, especially given the focused nature of our tests. In addition, since we used the default setting on all three products, it's impossible to say whether a bit of fiddling with any of the products would have produced significantly different results. However, if you held a gun to my head (or threatened to crush my beloved 3-chip DCR-VX2000), I'd have to say that SoundSoap was shockingly good.

Happily, you don't have to put your money down based on this extorted recommendation; all three vendors offer free, downloadable trial versions you can try on your own noise problems.