When you start taking videography and filmmaking seriously, you quickly realize how important sound is to your productions. One of the first steps you can take to improve your audio is to upgrade your microphone to a professional shotgun mic with an XLR connection. In this article, I'll explain how you can do this, even if your camera doesn't have XLR microphone inputs.
Making high-quality moving images with sound requires knowing a thing or two about using audio equipment. This is especially true when you're shooting footage with dialog. In order to hear your on-camera subjects clearly, a good starting point would be to outfit your camera with a professional shotgun microphone.
Before we segue into the world of professional shotgun microphones, it's important to determine what kind of mic input your camera has. If you're using a compact camcorder or a video-enabled DSLR, you likely have a 3.5mm mini-plug mic input. Professional microphones connect through XLR inputs— not mini-plug, so you first need to choose a piece of equipment to adapt an XLR mic to your camera.
In order to plug an XLR cable into a mini-plug input, many people buy an inexpensive 3.5mm to XLR adapter. This is not a good solution. The problem is that a small 3.5mm plug and a large, 3-pin XLR plug have different impedances. Poorly matched impedances will degrade your sound quality. Remember, you're on a mission to improve your audio, so properly matching impedances is really important.
When you adapt an XLR connector to mini-plug, you need a low-to-high impedance matching transformer. That may sound complex, but when you buy the right piece of equipment it's something you don't even have to think about. The most basic tool for this job is a simple adapter with a built-in transformer, like the Pearstone LMT100. You simply attach an XLR microphone cable to the XLR end of the Pearstone LMT100, and plug the mini-plug end of it into the mic input on your camera.
If you use a Pearstone LMT100, you will be limited to using only a single microphone. Also, if the microphone you want to use requires phantom power to operate, the LMT100 will not be able to power the mic. If you want the option to use more than one microphone, and you think you might like having features like phantom power and level controls, you'd be better off with an XLR adapter box.
As you can see in the photograph above, the XLR Adapter box mounts to the base of the camera. It screws into the camera's tripod thread. The camera and XLR Adapter can still be mounted to a tripod, because the XLR Adapter has a standard tripod thread at its base. In the photo above, the camera and XLR Adapter are mounted to a Manfrotto HDV501 head. An XLR Adapter box can be used on a tripod and removed to shoot handheld. They add to the bulk of the camera, but it's a good tradeoff considering that you'll have much better audio to match your picture.
Impedance transformers are built into the XLR Adapter box, so you never have to worry about losing sound quality due to a mismatch. In addition to enabling you to attach multiple XLR microphones to your camera, most XLR Adapter boxes allow you to plug line-level signals into your camera. For example, if you need to feed the signal from an audio mixing board at a wedding reception to your camera, having line-level inputs on your camera will be really handy. A couple of good choices for XLR adapter boxes with this feature is the Beachtek DXA-2T and the juicedLink CX211.
One of the big technical hurdles you may find yourself trying to jump over is a camera feature called AGC. AGC stands for Automatic Gain Control. In the most basic terms, AGC raises and lowers the audio level of the camera, to help avoid distortion when sounds get too loud, and to turn up the volume so you can hear softer sounds more clearly. AGC can be useful when you're shooting in noisy environments, when you don't have the opportunity to adjust your audio levels manually. However, in other situations AGC can be really distracting. When you're recording dialog in a quiet area, AGC will duck down the levels when a subject speaks, and in moments of silence AGC will start pumping up the levels. This creates an uneven ambiance, and it will irritate your viewers.
A few cameras (like the Canon 5D mkII) allow you to turn off the AGC, but the vast majority of cameras do not. To combat AGC, some XLR Adapters feature the ability to defeat it. They do so by feeding a constant tone into one of the audio channels on the camera. The AGC circuit on the camera hears the tone, and because it's a constant, unchanging sound, the AGC sits still and doesn't move the audio levels up or down. This allows you to record much more even-sounding audio on the other channel. There is one major drawback: because one of the audio channels on the camera is being used for the constant tone— you cannot use two microphones. But, if you're serious about getting good audio, the tradeoff is worth it. A single, well-positioned shotgun microphone can capture great sound.
There's a good variety of shotgun microphones available to choose from. As the mics go up in price, the build quality gets better and better, but what you're really paying for is sound quality. As you can see, there are different lengths of shotguns available. The longer they are, the more directional they get. If you plan on mounting the shotgun on top of your camera, you typically don't want to use a shotgun longer than 10 inches. Of course, this can vary depending on what kind of lens is being used.
A few things to keep in mind as you shop for a professional shotgun microphone are phantom power, handling noise and wind protection. Some shotgun microphones can be powered with an internal AA battery, while others require phantom power to operate. Phantom power is a small electrical charge that is sent out of the microphone input. It travels through the microphone cable and powers the capsule in the shotgun. Mics that can only be operated with phantom power have a slightly lower noise floor. This is a good thing. The lower your noise floor is, the cleaner your audio will be. Mics that run on AA batteries can plug into more equipment (namely XLR adapters that can't supply phantom power).
When you mount a shotgun microphone to a camera, you have to be really mindful of vibration and handling noise. Shotgun microphones are very sensitive, therefore when you mount one to a camera it's necessary to use a shock mount. A shock mount suspends the microphone with rubber bands, which eliminate most of the vibration and handling noise the mic would otherwise pick up. To take the guesswork out of choosing a shotgun microphone, a shock mount and the cable that you need to plug it in, B&H has created some kits with all of these items included.
The Rode NTG-2 and the Audio Technica BP4073 are popular choices for both on-camera and boompole use. The NTG-2 can be powered with either an internal AA battery or with phantom power. The BP4073 requires phantom power to operate. Both kits include the Pearstone DUSM-1 shock mount, as well as a short right-angle XLR cable. The 1.5' cable is the perfect length for mounting a shotgun mic to your camera.
Upgrading to a professional shotgun microphone and properly adapting it to your camera can do wonders for your sound quality, but sometimes improving your tools is only half the battle. Mounting a shotgun microphone directly on top of your camera will produce decent-sounding audio, but when you have a person speaking to the camera— or if you're shooting a scene with dialog, you will get much better-sounding results if you use a boompole to get your pro shotgun microphone closer to the speaking person's mouth.
Even though shotgun mics do a good job of capturing sounds emanating from a few feet away, when you're shooting footage with dialog, it really behooves you to get the microphone closer to the action. The best way to do this is to attach the mic to a boompole and hoist it over the heads of your on-screen talent. This practice may seem antiquated and crude, but it works really well, and it's still the best way to achieve good dialog audio.
If you're going to be shooting footage with dialog, picking up one of these B&H complete boompole kits is a really good idea. You get everything you need to get booming with a single purchase. These kits also come with all the necessary items to operate the shotgun while mounted on your camera. A carrying/storage case is included, as well as a pistol grip, which can be useful for operating the shotgun off of the camera in situations where boompole use isn't practical.
The complete boompole kits also include softie windscreens for the shotguns. Using advanced wind protection is absolutely necessary for outdoor shooting. Remember, shotgun microphones are very sensitive. If they're exposed to wind, the audio they pick up will be terribly distorted. Every shotgun microphone comes with a basic foam windscreen, but this isn't going to cut it for outdoor use. More involved wind protection is critically important.
I hope this article was helpful. If you have any questions at all about upgrading to a professional shotgun mic, we encourage you to post them in the Comments section below.