Technology: Wireless microphone systems
Technology: Wireless microphone systems
We asked René Mørch from DPA Microphones and Sean Meagher of Samson Technologies about wireless microphone systems
How do you define a wireless microphone system?
René: A microphone connected to a transmitter and a receiving unit, offering one or more channels.
Sean: A wireless microphone system transmits audio from a microphone transmitter to a receiver, eliminating the cable from the signal path, allowing live performance freedom.
What do wireless mic systems consist of?
Sean: There are three main components: the microphone, the transmitter and the receiver. The microphone can be integrated into the transmitter. The most common [setup] is a handheld vocal microphone and transmitter, but Samson also makes transmitters that are integrated into headset and single earset mics as well.
René: Everything that isn’t a wire! Basically, it is a transmitter, receiver, antenna distribution units (assuming they are not integrated), antennas and a remote GUI – for example an iPad or a PC – so you can control it.
What are the advantages of wireless?
Sean: Wireless mics give the live performer freedom to roam without being tethered and it reduces the clutter of running cables all over the pulpit. There are also multichannel systems that can have two or four receivers in a single unit with a mixed output, reducing the number of mixer inputs needed for multiple performers.
René: The person using it can move wherever they want without being constrained by a physical wire. For preachers, this means they can easily interact with their congregation and get closer to them. Also, if you are using a headset microphone or a lavalier, you have your hands free, so you could be doing other things such as holding a book. Another advantage, especially with headsets, is that your tone of voice doesn’t change because the microphone is always the same distance and place from your mouth.
What are the drawbacks?
René: They are more expensive but you do get what you pay for. Security, for example, comes with a price tag so if you want a system that ensures no dropouts or interference, you will pay more. Also, wireless spectrums can get cluttered and a frequency that might work in the morning won’t work later in the day when the nearby theatre turns on its wireless system and starts occupying the space. This can result in interference and you may even end up broadcasting each other’s sound. Look at a spectrum analyser to find the spot that has the most space. An inexpensive unit doesn’t have this feature but simply suggests appropriate frequencies to use, where it detects less nearby traffic. More expensive digital systems now offer a frequency hop feature that automatically shifts you to a clearer frequency.
Sean: Wireless systems use batteries that need to be replaced or recharged. We recommend installing fresh batteries (or fully charging the system) before each session to ensure optimal performance. They also have ranges from 100–300 feet depending on the type of system and RF (Radio Frequency) environment; once the performer goes out of range, the user can experience dropouts.
What is the frequency spectrum and its restrictions?
Sean: Transmitters and receivers must always operate on the same channel. Where multiple transmitter/receiver systems are used, each must operate on a different channel. However, there are limitations as to how many systems can be used at any one location and which frequencies can be used by each system. This is due to the problem of intermodulation, where one radio signal can distort another through the introduction of new, unwanted RF signals. When using multiple systems, follow a channel plan from the manufacturer that is designed for multiple systems or perform a wireless frequency scan to find the clearest operating channel, if the system has the feature.
Understand what frequency bands are legal to operate wireless microphones. A number of previously legal bands in the US have been auctioned off or designated for other use by the FCC. When using multiple wireless systems, be aware of what frequencies might be problematic because of nearby TV stations.
René: Seek information and/or professional guidance to fully understand the restrictions in your area. Maximise their investment by making sure your system is upgradable and will therefore last for more than a year or two, especially as governments often introduce frequency alterations to free up space for other businesses.
What else do HOW technicians need to know?
René: Make sure your system can cope with high-quality microphones and that you have invested in the best microphones you can afford, because the microphone is the start of the audio chain and, if you don’t pick up great audio to begin with, it is never going to sound good.
Most modern wireless systems offer decent quality and the higher-end systems are almost on par, in terms of audio quality, with wired solutions. Your microphone should be fit for purpose, both in terms of its physical appearance and also in terms of the electrical and acoustical interface to the transmitter. It is important to match the sensitivity of the microphone, its self-noise and its maximum SPL handling to the capabilities of the transmitters. The dynamic range of a good-quality transmitter is typically higher than the microphone’s capabilities so, to get the best from your wireless system, you need to establish proper gain structure and set the correct input levels between the transmitter and the mic.
Sean: In large, multichannel wireless systems, technicians can greatly simplify antenna connections with the use of a passive antenna splitter or an active antenna distribution amplifier. They allow multiple receivers to share the same pair of antennas (though each receiver must still be tuned to a different channel), thus facilitating faster, more compact set ups by reducing the number of antennas. Many antenna distribution amplifiers also serve to increase the active range by adding a certain amount of RF gain for a stronger, quieter signal.
Another way for techs to maximise the active range of a system is through the use of remote antennas, particularly powered antennas. The purpose of a powered antenna is to improve receiving sensitivity while at the same time reducing interference. By using remote antennas, the receiver can be placed almost anywhere (within reasonable limits dictated by your cabling); for example, near the audio equipment so that the sound engineer can have immediate access to it if adjustments are necessary during performance.
This article was first published in the May-June 2019 edition of Worship AVL. Subscribe at www.proavl-central.com/subscribe/worship