Boom Mic Roundup

What is a Boom Mic?

No, this is not a mic that explodes. Yet plenty of people have used them to capture the sound of some sort of explosion! Boom Mics, also known as Shotgun Mics or Rifle Mics, are those that are predominantly used on top of a pole to capture audio when videoing. You will have seen plenty of film shots where there is someone attempting to hold a microphone steadily on the end of a long pole. This person is known as the Boom Operator and they would work in conjunction with either a separate Camera Operator, or Sound Recordist or both. Their job is to keep the microphone centred squarely on the action so that the dialogue is crystal clear. Boom mics (although not specifically on a boom pole) are often used for sound capture in sports broadcasts, nature recording and theatres. This is often when the mic is referred more as a shotgun mic instead of a boom mic.

The Anatomy of a Boom Mic

Boom mics come is all shapes and sizes, although the traditional type resembles a long barrel with slits down the side. These mics are mainly designed to capture sound at a distance, whilst rejecting the sound around them. The back end of the mic typically houses the electronics and power regulators, as well as the output connection(s). It’s the front portion of the mic that usually holds the key to its success. Apart from the actual mic capsule, the barrel as mentioned previously will usually have a series of slots running down it. These are designed in such a way that sound reaching the microphone capsule from this source is out of phase from the sound reaching the capsule from the front. This has the effect of cancelling out the sound received from the sides.

Longer isn’t always better!

Hold the jokes please… There is a common misconception that the longer the shotgun, the better it is. Whilst it is true that longer boom mics are more directional then shorter ones (within the same range), this may not suit your application. For example, you many actually want to capture some of the ambiance, in which case a shorter, wider response mic may be desirable. Also, a very long-barrelled microphone may end up in shot if you have restricted space available to you.

What’s That Noise?

One of the most annoying results when recording sound is unintentionally also picking up noise that is unwanted. This could be background noise which is avoidable by simply quieting the person making the noise, or waiting for other noise to stop. It could also be caused by the mic picking up stray RF signals such as those produced by a mobile phone in close proximity to the microphone. To avoid this situation, look for a mic that offers RF shielding – usually only available on Broadcast Shotgun Mics.

Let’s Get Connected

One of the most common questions we receive at TheMicStore, is ‘How do I connect the boom mic?’. Here we need to talk about the difference between consumer boom microphones and professional versions. Consumer versions are typically expecting to connect to a 3.5mm jack plug on a camcorder or camera. These connections are usually unbalanced, which essentially means that the longer the cable used to connect between the mic and the recording device, the more background noise will be picked up. Our own rule of thumb on this is that this connection should be kept lower than 7-10 metres. Anything more and you are likely to be able to audibly hear a background hiss on your recordings.

Professional boom mics are likely to have what is known as an XLR connection. This is a 3-pin balanced connection and does not suffer from the same noise concerns providing the signal path remains balanced all the way to the recording device. It is possible to use an XLR microphone with a 3.5mm input, however unless the input on your device is also balanced, the sale rule will apply regarding maximum cable lengths.

Have You Got the Power?

Most boom mics will need power for them to work. This can be in one of two forms. Either the microphone can be battery-powered internally, or power can be supplied to the mic from the recording device or camera. This is frequently known as Phantom Power. Battery-powered boom mics are typically used with consumer-grade equipment. Professional cameras or recording devices will often have the ability to supply phantom power to the microphone, and for many professional microphones, this is the only way to make the mic work. If you do not have phantom power available, but want to take advantage of the higher-quality specifications of a professional mic, you can opt for a portable phantom power device.

I’ve Got Two Ears but Only One Mouth!

Do you need a stereo or mono microphone? Well let’s consider the facts. If you are recording an interview, chances are your interviewee has only the one mouth. So why would you ever need stereo? Some applications for boom mics involve capturing the sound around us (or at a distance) in a way that makes it sound like you are actually there. This is most relevant if you are using the mic for wildlife recording, or maybe action scenes such as sports filming. In this case, you many want to choose a stereo mic rather than mono. If all you are doing is dialogue based, it’s fairly safe to assume that you just need a mono mic.

Other Considerations…

The only other things to think about when choosing a boom mic, is how it is going to be mounted, held and protected. When a microphone is hovering above the heads of the action, it is all too easy to wobble the mic, or knock the pole it is mounted on, which will result in the mic picking up unwanted sounds. Boom operators will therefore often employ the use of some form of microphone suspension. These devices essentially hold the microphone in an elasticated cradle which absorb knocks and other vibrations.

So now you have the microphone, it is adequately isolated from vibrations, and you need to get it up off the ground. This is where you’ll need the help of a boom pole. These come in a range of lengths and weights, and will be typically made of either aluminium or carbon-fibre. Aluminium is a good lightweight material but does not have the strength of carbon-fibre, and therefore if the boom pole is to be used regularly, carbon-fibre may be a better long-term choice.

The final consideration will be to do with wind noise. Whilst in an ideal world the weather will be beautiful with not a breath of wind, in the UK this is rarely the case and certainly cannot be relied upon! So you should consider the use of some form of microphone windshield. These will either fit directly to the mic or be part of a suspension-mount kit, and will be specific to the size of the boom mic.

But there are so many choices…?

We know that there are lots of models out there, but by choosing what type of mic you need based on the information above, the perfect model is right around the corner. So why not call TheMicStore on 0800 098 8079 and we’ll work it out based on your own individual requirements.

 

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