Shotgun Microphones

Published Tuesday, May 24, 2011 - 11:50am

What is a shotgun microphone?

A shotgun is a long, cylindrical microphone that excels at picking up sounds in front of it, while rejecting sounds to the sides and rear. Shotguns are designed to have a narrower focus than an average microphone. Shotgun microphones do a great job of picking up the frequencies the human voice produces. Their sound grabbing and voice-capturing abilities make them a great choice for picking up on-camera dialog.

When would I use a shotgun microphone?

Shotgun microphones are most commonly used when you cannot position a microphone directly in front of a sound source. For example, if someone is speaking in front of a video camera and you don’t want them to hold an interview microphone up to their mouth, having an off-screen shotgun mic is a great option. Shotguns are commonly used in film and video production, as well as in live theater, sound reinforcement and in the creation of sound effects. Shotgun mics reject a certain percentage of ambient noise, but retain enough to render a richness that sounds natural.

Do shotgun microphones have any downsides?

A shotgun microphone’s ability to reject ambient sound is frequency dependent; meaning that they do a good job of rejecting high and midrange frequencies, but they don’t reject bass frequencies as well.

Most shotgun microphones have a “rear lobe” in the back: they pick up sound primarily in the front, but they also pick up a little sound from the rear. If you have a shotgun microphone mounted on a video camera, the camera operator needs to be aware that the mic will pick up the sounds they make as well. Another example is when a boom operator is hoisting a shotgun microphone up near a ceiling. They need to be mindful of ducts and other fixtures that may be creating noise behind the mic, as well as to listen for sound reflections that may be creating an unnatural ambience.

As mentioned before, shotgun microphones do a good job of picking up the mid frequencies of the vocal range, but they’re not the best choice for recording musical instruments and other more dynamic sounds.

How is a shotgun different from other kinds of microphones?

The thing that really makes a shotgun different from other kinds of microphones is its long “interference tube.” It’s basically a long, vented tube that‘s positioned in front of the microphone capsule. The length of the interference tube is usually an indicator of how much “reach” a shotgun microphone has; the longer the interference tube, the more focused it will be, but it will not amplify a very distant sound. One downside to longer interference tubes is that they often strip away the natural quality of the sound. However, this is not a rule. Some higher-quality long shotguns capture great-sounding audio.

Does a shotgun microphone “zoom” into a sound?

People often assume that a shotgun microphone is a “zoom microphone.” This is not the case. Shotgun microphones do not actively chase sounds. They are not the audio equivalent of a photographic telephoto lens. Even though shotgun microphones do an above-average job of picking up sounds that originate from a short distance away, they all sound better when they’re physically close to the sound source. That’s why a skilled boompole operator will always strive to get the shotgun microphone as close as possible to the sound source, which often means hovering right at the edge of the frame of a shot.

What is the best way to position a shotgun microphone?

The ideal position for a shotgun microphone is as close to the speaking person’s mouth (or other sound source) as possible. If a shotgun is more than three feet away, the audio will start to sound distant. The farther away the shotgun is, the more distant and reverberant the audio will become. That’s why one of the biggest challenges you face when using a shotgun microphone is getting it as close as possible to the sound source. That’s why boompoles, pistol grips and boompole C-stand mounts are all regularly used.

Can I mount a shotgun microphone to my camera?

Mounting a good shotgun microphone to a video camera is usually a smart idea, simply because the mics that are built into camera usually don’t sound too good. The improvement in sound quality over the built-in mics is great, but it’s important to understand that any sound source which isn’t directly in front of the camera is still going to sound far away, even when you use a high-quality shotgun microphone. The challenge of keeping the audio clear and intelligible for your audience is a constant one, and there is no set-it-and-forget-it solution.

What is “handling noise” and how do I avoid it?

When you mount a shotgun microphone to anything (be it a camera, a boompole or otherwise), you have to be really mindful of vibration and “handling noise.” Shotgun microphones are very sensitive. When you mount one to a camera, it will pick up the sounds of your hands as they support and adjust controls on the camera. Therefore it's necessary to use a piece of equipment called a “shock mount” to attach the microphone. A shock mount suspends the microphone with rubber bands (or utilizes similar kinds of suspension systems), which eliminates most of the vibration and handling noise the mic would otherwise pick up.

We strongly recommend that you use a dedicated shock-mount accessory to fasten a shotgun to a camera, as opposed to using the microphone clamps that are sometimes built in. The microphone clamps built into cameras do not provide enough suspension for higher-quality shotgun microphones, and your audio will be riddled with unwanted noise if you don’t use a proper shock mount.

How does a shotgun microphone connect to a camera?

There are essentially two kinds of shotgun microphones: consumer and professional. Consumer shotgun microphones connect with a 3.5mm mini-plug jack. Professional shotgun microphones connect with a three-pin XLR jack. If you’re connecting a shotgun microphone to a camera, it’s really important to determine what kind of microphone input your camera has, so that you know which microphones will be compatible.

Does a shotgun microphone need power to operate?

Most shotgun microphones have “condenser” elements which are responsible for picking up the sound. This kind of microphone element requires power to operate. Some condenser microphones require a battery, while others need to draw power from the device into which they’re plugged.

Consumer and professional shotgun microphones that don’t operate on battery power require different kinds of external power. Non-battery powered consumer shotgun microphones require the camera or device they’re plugging into to provide them with “Plug-In Power.” Non-battery powered professional shotgun microphones require the camera or device they’re plugging into to provide them with “Phantom Power.”

What is “Plug-In Power” and why would I need it?

Plug-in Power is a small electrical charge that travels through the cable to power the microphone. It’s exclusive to consumer microphones that connect with 3.5mm jacks. Plug-In Power is typically something that you don’t even have to think about. You plug in the microphone, and if the input supplies Plug-In Power, the microphone will operate and that’s it. However, not all 3.5mm mic inputs supply Plug-In Power. If a device has a 3.5mm mic input but lacks Plug-In Power, a non-battery powered consumer microphone will not work in this input.

What is “Phantom Power” and why would I need it?

When the device that a professional shotgun is plugged into is supplying it with electricity, the charge is referred to as “phantom power.” Many professional video cameras that feature XLR mic inputs will also feature phantom power. Because only certain kinds of microphones require phantom power, the camera will also have a switch to turn it on and off. Phantom power is also commonly found on audio mixers and computer audio interfaces. Phantom power tends to intimidate beginners because it just sounds spooky. Fear not. Using phantom power is about as complicated as flipping a light switch to turn on a table lamp. Besides being called phantom power, it is also referred to as “+48V.”

What is “wind protection” and why do I need it?

The term “wind protection” applies to any additional accessories that are designed to keep wind and drafts of air from distorting your audio. Using robust wind protection is absolutely necessary for outdoor shooting. Remember, shotgun microphones are very sensitive. If one is exposed to wind, the shotgun won’t be damaged but the audio it picks up will be terribly distorted.

Every shotgun microphone comes with a basic foam windscreen, but this isn't enough protection for outdoor use. Purchasing additional heavy-duty wind protection is critically important. Even a gentle breeze on a calm day will distort the audio that an under-protected shotgun microphone picks up. There are many names for different kinds of wind protection: wind jammers, softies, dead cats, smoothies, blimps, zeppelins, etc. When you’re estimating the budget of a complete shotgun microphone rig, it’s strongly advised that you factor in the cost of buying proper wind protection.

Are there any controls to adjust on a shotgun microphone?

Some (but not all) shotgun microphones will feature a miniature switch or two. On professional shotgun microphones the switches are almost always recessed into the cylindrical body of the mic. The switches on consumer shotgun microphones aren’t always recessed, and are sometimes found on the rear or base of the microphone.

What is a “Low Cut” switch, and why would I use it?

The most common switch on a shotgun mic is a filter. The filter is sometimes referred to as a “High Pass Filter” or a “Low Cut” switch. These are both the same thing. When this switch is engaged, the activated filter will remove low frequencies from the audio that the mic outputs. Low frequencies are often undesirable, and they’re usually unnecessary for dialog.

A shotgun microphone will pick up more low frequencies than you can hear in any given location. For example, a shotgun will sometimes capture the rumble of distant vehicles, and unnaturally deep sounding footsteps. These sounds can be really distracting to a viewer on normal speakers, and the subwoofers in surround sound systems make it far worse. That’s why it’s usually a good idea to engage the low cut filter if your shotgun mic features one.

What is a “Pad” switch, and why would I use it?

Another common switch is a “pad.” A pad simply makes a microphone less sensitive to loud noises (or in layman’s terms, it turns down the volume of the mic). If you’re using a shotgun microphone in a noisy location such as an active factory or a live band performance, it’s usually a good idea to engage the pad switch. You just need to be mindful to disengage it when the loud noises stop; otherwise the output of the microphone will be unnecessarily low.

Why would I need a switch that allows me to increase the volume?

A few shotgun microphones give you the option to increase the sensitivity of the mic (or in layman’s terms, turn up the volume of the mic). This can be useful if you’re using the shotgun in a really quiet location, where distant sounds are barely audible. You’re more likely to capture quiet sounds if you can boost the sensitivity of the mic.

If the camera or recording device that you’re plugging into allows you to turn down the input level manually, boosting the sensitivity of the shotgun microphone can sometimes help you capture better-sounding audio. The quality of sound that you achieve with any given microphone is partially dependent on how good sounding the “microphone preamp” is on the device that you’re plugged into. A mic preamp is just a small amplifier that raises the soft mic-level signal coming out of the mic up to line level so it can be properly recorded. For example, if the camera you’re plugging into has a noisy, low-quality mic preamp, you may get a better sound if you turn down the input level in the camera manually and engage the sensitivity boost switch on the shotgun mic.

What makes one shotgun microphone better than another?

The trite phrase, “you get what you pay for” applies to shotgun microphones as well. Better-quality shotgun microphones will be put through more rigorous testing during their design phase, made with higher-quality materials and components, and subjected to strict quality-control testing before they are sold. Shotgun microphones are often used in the field, so they have to be durable, especially since the term “in the field” could be anywhere from the Sahara Desert to the Arctic Pole.

While construction and durability are major factors, the attribute that always makes one shotgun microphone more desirable than another is how good it sounds. The better sounding the mic, the more expensive it is likely to be.

The Takeaway

• A shotgun is a long, cylindrical microphone that excels at picking up sounds in front of it, while rejecting sounds to the sides and rear.
• Shotguns are designed to have a narrower focus (sometimes referred to as more “reach”) than an average microphone.
• Shotgun microphones do a great job of picking up the frequencies the human voice produces.
• Shotguns are commonly used when you cannot position a mic directly in front of a sound source.
• Shotgun microphones are used in film and video, live theater, live sound and in the creation of sound effects.
• Shotguns do a good job of rejecting high and mid frequencies, but they don’t reject bass frequencies as well.
• Shotguns have a “rear lobe,” meaning they pick up sound primarily in the front, but also pick up a little sound from the rear.
• Shotguns aren’t the best choice for recording musical instruments and other dynamic sounds.
• An interference tube is a long, vented tube that‘s positioned in front of the microphone capsule.
• A shotgun microphone is not a “zoom” microphone.
• Shotgun microphones always sound better when they’re physically close to the sound source.
• The best place for a shotgun is as close to the speaking person (or other sound source) as possible.
• If a shotgun is more than three feet away from a sound, it will start to sound distant.
• Shotguns are a big improvement in sound quality over the built-in microphones in a video camera.
• It's necessary to use a “shock mount” to attach a shotgun mic to a video camera or boompole.
• Consumer shotgun microphones connect with a 3.5mm mini-plug jack.
• Professional shotgun microphones connect with a three-pin XLR jack.
• Plug-in Power is an electrical charge supplied through a mini-plug input for consumer mics.
• Phantom Power is an electrical charge supplied through an XLR input for professional mics.
• A basic foam windscreen isn't enough protection for using a shotgun outdoors.
• Using additional robust wind protection is absolutely necessary for outdoor shooting.
• When a “High Pass Filter” or a “Low Cut” switch is engaged, the low frequencies are removed.
• When a “Pad” switch is engaged, the shotgun will be less sensitive to loud noises.
• More expensive shotgun microphones typically sound better than low-cost ones.

Published BHphotovideo/ProAudio