How to choose a wireless microphone?

JTS R4 Professional wireless mic system

I have been using and installing wireless microphone systems for over 30 years, and in that time I have seen wireless technology grow from vhf systems with a couple of channels to modern 16 channel systems.

Choosing the right wireless microphone for you is not just about the best technology, it is also about ease of use and probably budget as well.

In this article my aim is to give you enough knowledge to make an informed choice, and to offer a few suggestions from personal experience.

Terminology

Whether they are referred to as 'Wireless microphones', 'Wireless mics', 'Radio mics' or 'Roving mics' they all refer to the same thing. That is a Receiver that is connected to the PA system by wires, and a transmitting microphone that communicates with the receiver using wireless radio frequencies.

Typical professional wireless receiver

A wireless receiver that connects to your sound system using a microphone cable

Audio Technica Handheld Transmitter

A wireless handheld transmitter that connects to the receiver using a wireless radio link

Audio Technica Belt Pack Transmitter

A wireless belt pack transmitter that connects to the receiver using a wireless radio link

A 'Tie mic', 'Tie clip mic', and 'Lavalier Mic' refer to a miniature microphone that is normally clipped to clothing (but could be worn on a lanyard). These microphones rely on a separate transmitter pack, usually designed to be clipped onto a belt, hence the name 'beltpack'.

Audio Technica Tie Mic or Lavalier Mic

The handheld wireless mic combines the microphone and transmitter into a single package not much bigger than a standard handheld such as the Sure SM57.

Headworn mics can come either has heavy clunky things best left to aerobics tutors or much more discrete wire framed headsets. The use of wire framed headsets is recommended as the mic turns with the wearers head, so pickup is maintained. These too rely on a beltpack.

Wire Frame Headset Mic

Beltpacks contain the transmitter for microphones or other sound sources to plug into and send signals to the wireless receiver. They can be worn on your belt, in pockets provided the aerial is not tangled up, or under clothing. Keep in mind they work best if you avoid placing anyone between the transmitter and the receiver.

The Basics of how a wireless microphone works

Radio Frequencies

Wireless microphones, mobile phones, Wifi devices, Bluetooth and Satellite TV all broadcast their signals using radio waves. Like our roads where there is a limited amount of space to carry cars, there is a limited number of radio frequencies available to carry signals.

To avoid wireless chaos international standards have been agreed to say which frequencies wireless microphones can use. With more and more commercial pressure from the mobile phone companies the space for wireless mics has been squeezed tightly.

Here in the UK we have:

  • channel 70 (863 to 865 Mhz) free to use with no licence and room for 3 to 4 microphones depending on the local radio traffic
  • channel 38 (606.500 - 613.500 MHz) which requires a licence, and room for 12 to 16 microphones
  • VHF 173.8 - 175 MHz, free to use with room for 2 mics and the most likely to suffer from interference
  • Digital 2400 - 2483.5 MHz shares its space with computer WiFi and other wireless devices.
Radio Mic Frequencies UK
Channel Frequencies Licensed No. of Mic's
VHF 173.8 - 175 MHz none required 2
Ch 38 606.500 - 613.500 MHz £85 per year (2019) 10***
Ch 70 863 - 865 MHz none required 4*
Digital 2400 - 2483.5 MHz none required 10**

* Although 4 systems are possible, in practice it may be limited to 3 in close proximity to mobile masts

** Up to 10 channels are possible, the max number may be limited in close proximity to wireless data networks

*** Offcom have a 10 channel plan that shows 10 mic's can be used concurrently, some manufacturers say they can provide more

Channel 38 systems require a uk wireless microphone licence

 

Cheap wireless systems that use VHF should be avoided, many churches still rely on old VHF systems installed 10+ years ago, and they remain usable due to the remote locations of many churches.

Channel 70 or free to use systems were very popular because they avoid the £85 licence fee, however, the government only confirms availability of this channel on a rolling 12 month period. This means that equipment purchased now only has a guaranteed service life of 12 months. There is no compensation scheme to users who buy now and find the channel made illegal in 12 months. There is another problem, 4G phones and 4G transmitter booster stations in close proximity to this band can render it unusable or restrict the number of microphones that can be used. This is expected to get worse with the roll out of 5G.

Channel 38 licensed systems work in protected frequencies and the government has established the principle of compensation if they move the frequencies. You can have up to 16 wireless systems in this band shared between microphones and wireless in-ear monitors.

Digital systems use the same frequencies as WiFi routers, and the more digital wireless systems are in use the less space for WiFi networks, 10 microphones would block any WiFi at all.

Receivers and Transmitters

All analogue receivers are tuned to listen on a particular frequency for a signal from the matching transmitter. There is no security built in and so any suitable receiver could in theory eavesdrop. If a specific manufacturer was to encode the signal being sent then only their receivers would be able to make sense of the signal.

Digital receivers encode the information being sent to and from each receiver and transmitter, it is not the frequency that links them but the content of the digital signal. Digital systems have a few milliseconds delay which analogue systems do not. More digital frequencies are used as the number of mics increases.

Diversity receivers have two antenna and work by choosing the strongest radio signal between the direct line of sight signal and a signal reflected off the surfaces of a building. So if your performer turns so that their body is between the receiver and transmitter a diversity receiver may still get a signal.

So how do I choose the best system for me?

  • Everyone should avoid VHF systems
  • If you cannot afford the annual licence fee these are your options:
  1. If you operate in a building where line of sight cannot always be maintained then choose channel 70
  2. If you can maintain line of sight and WiFi access is not important then you can to go digital
  3. If you need more than 4 microphones you would have to go digital
  • If you can afford the annual license then it makes sense to choose channel 38 because of the lack of interference, its protected status, and the greater number of channels available

Will a cheap system do?

In this case you really do get what you pay for:

  • Budget entry level models without diversity receivers and cheaper components wont last as long or cope with difficult buildings and are more prone to interference.
  • Intermediate models with more complex circuitry and true diversity receivers that are more reliable
  • Professional systems with higher power transmitters and built to cope in demanding environments

I would not recommend purchasing a budget entry level model, we have a range of intermediate level and professional level wireless microphones for sale

So how do I choose the best style of wireless mic for me?

  • If you are a professional sound engineer then having a combination of lavaliere, headworn wire headset, and handheld is essential
  • If you are a travelling speaker with your own sound system the using a lavaliere or headworn wire headset would be best, the latter especially if you are turning your head to look at projector screens.
  • For interaction with audience or congregation members the a wireless handheld works best.
  • If you are buying wireless microphones for a church then most churches I have advised or installed systems into have used two tie mic and two handheld systems, with additional systems if they have worship musicians and singers.
  • Primary schools are best using handhelds for the youngest children and the tie mics being more fragile reserved for teachers
  • Theatres and Drama workshops would be best off using wire frame headsets.

 

Add comment