This installment of our blog series on Basic Audio Techniques for Video explains the basics of working with wireless mic systems. If you missed the previous installment discussing how to avoid wind noise when recording outdoors with lavalier microphones, you can read it here. In order to produce a great video, you need great sounding audio to go along with your picture. In some instances, a wired microphone may not make the most practical sense, or you may simply prefer the freedom of movement a wireless mic offers. There are some simple techniques to help get the best performance from your wireless microphone systems.
Wireless Microphone Basics
It’s always important to ensure that you have a copy of the manual that matches your wireless mic system. There is a wide variety of makes and models for wireless mics and not all are created equal. Some instructions can even change from model to model within the same brand. There are some basics that are common among most models, however, specific menu settings and buttons may vary across different manufacturers and models.Batteries
The most common issues with wireless mics on a shoot are the result of weak batteries, especially in the transmitter. Start every recording session with a fresh pair of batteries in your units. Plan to swap out the batteries for a fresh pair about four hours into your shoot, perhaps around lunchtime, until you get more familiar with a particular unit’s battery life. Most manufacturers advise against the use of common rechargeable NiCad or Nickel Metal Hydride cells. These types of batteries tend to drop to a low voltage level fairly quickly, even though they are able to hold a lower voltage for a long duration. Fresh alkaline batteries start off with a higher voltage that diminishes much more gradually. Not having to worry about recording audio with a low battery makes for a less stressful recording experience. Some models, such as the System 10 camera-mount wireless system, utilize a built-in lithium ion rechargeable battery in the receiver that can operate for up to 12 hours. In order to make them last the duration of your shoot, ensure they’re fully charged the night before. While it’s possible to power them from a portable USB battery pack in a pinch, it’s easier not to worry about charging them while recording.Frequencies
After completing your battery check set all your wireless mics to the best operating frequencies. All pairs of traditional UHF receivers and transmitters need to be set on matching frequencies. To start, select a frequency for your first system and leave them turned on. Then, scan your next receiver to choose another frequency and set the matching transmitter. Continue this process for all the systems to be used in the shoot. Remember, there’s a wide variety of frequencies to choose from, so you can allow some space in between them. Keep your systems organized by labeling receivers and transmitters that are in the same set. There may be other radio devices on or close to your chosen frequency. One way to detect interference is to turn off the matching transmitter and watch the indicator light for each receiver antenna. When the transmitter is turned off, neither light should come on at all. If either antenna light shows any activity, it’s picking up an unwanted signal. It can also help to listen to the receiver for any electronic chatter. All manufacturers include additional frequency information in the manual or online for easy reference. Some of the newer systems on the market operate in the 2.4 GHz range and are frequency adaptive. They automatically change frequencies to avoid interference. Simply pair those systems to each other.Mics
Your choice of which lavalier to use will greatly affect the overall sound quality of the audio, regardless of whether you’re using a wireless or hardwired system. To set the microphone input level on the wireless transmitter:- Plug your headphones into the receiver. Start with the knob turned to the lowest possible position.
- While speaking into the mic, raise the level gradually until it begins to sound clear and bright.