Why does the selection of a wireless system start with the application?

First, it is necessary to determine who will be using the microphone, how they will be moving, and how critical the reliability of the transmission is. Only then can a specific series of devices be chosen.

When selecting, the following factors are important:

• vocal or speech,
• number of transmitters,
• size of the stage,
• distance from antennas,
• ability to run a cable,
• requirements regarding the appearance of the microphone,
• presence of IEM,
• number of other RF systems.

A presenter standing at a lectern has different needs than a frontman moving around the entire stage. Meanwhile, a conference with eight microphones is not simply an eightfold version of a single-channel system – as the number of devices increases, frequency, intermodulation, antennas, and RF monitoring become increasingly important.

Therefore, professional selection should start from the event scenario. 

Handheld microphone, bodypack, or headset?

 The type of transmitter should depend on how the user works during the event. A handheld microphone provides direct control over the distance from the mouth, a bodypack allows connecting a lavalier, headset, or instrument, and a headset keeps the capsule in a fixed position relative to the voice.

Vocal

For a vocalist, the most natural choice is usually a handheld transmitter with a suitably matched capsule.

The advantages are:

• known working method,
• control over the distance from the mouth,
• the ability to consciously use the proximity effect depending on the capsule,
• no bodypack and cable near the body.

In a loud stage environment, the directional characteristics of the capsule, the way the microphone is held, and monitoring are particularly important.

The system should also withstand the dynamics of the vocalist without overloading the input path.

Presenter

A presenter often needs free hands, which is why a bodypack with a headworn or lavalier microphone is used.

A headset keeps the capsule close to the mouth and in a relatively fixed position. This way, the volume level is less dependent on whether the speaker turns their head or moves around the stage.

A lavalier is visually more discreet, but it is located further from the mouth and may pick up more ambient sound and reverberation.

Therefore, the choice between a lavalier and a headworn microphone should consider not only appearance but also the acoustics of the room and the required gain before feedback.

Panel discussion

In a panel discussion, the problem becomes the number of simultaneously open microphones.

You can use:

• handheld microphones,
• lavalier mics,
• headsets,
• table solutions, depending on the format.

If the panelists are to speak freely without passing microphones to each other, each may need their own channel.

Then, in addition to choosing the capsules themselves, you need to consider managing multiple microphones. A greater number of open channels means more collected reverberation and room sound, so the mixing method and use of an automixer can be very important.

Instrument

A bodypack can also be used for wireless transmission of the signal from an instrument, e.g., a guitar or bass.

However, it should not be assumed that every microphone bodypack is automatically suitable for every instrument.

You need to check:

• type of input,
• signal level,
• impedance,
• appropriate cable,
• gain adjustment range.

The instrumentalist has a lot of freedom of movement, but the system still needs to be considered in the overall RF coordination.

How many wireless channels do we need?

 The number of channels should correspond to the maximum number of transmitters that may be needed simultaneously, along with a reasonable buffer based on the event scenario.

It's not enough to just count the people.

For example, a conference may include:

• two hosts,
• four panelists,
• two microphones for audience questions,
• one backup handheld.

That's already nine potential channels, even though not all will be constantly active in the mix.

At the concert, you need to count:

• vocals,
• wireless instruments,
• guests,
• talkback, if using RF,
• possible backup transmitters.

The larger the system, the more important it becomes to check how many compatible channels can actually operate simultaneously in the available spectrum. You should not buy or rent several independent sets without checking if their ranges and frequencies allow for a common configuration.

Analog or digital wireless system?

Analog and digital systems can be used professionally, but they differ in how audio is transmitted and the behavior of the path. You should not choose solely based on the phrase "digital = better".

In classic analog systems, companding is used, which is dynamic compression before transmission and its playback on the receiver side. Digital systems do not require such a process and can offer a wide audio bandwidth and high dynamics. On the other hand, digital transmission introduces a certain latency, the value of which depends on the specific design.

When choosing, it is worth analyzing:

• audio quality,
• latency,
• RF resistance,
• spectrum efficiency,
• number of compatible channels,
• encryption, if needed,
• monitoring and management capabilities.

A high-end digital system can handle complex multichannel productions, but a simple digital system operating, for example, in a shared band with other devices may not be the best solution for a large concert.

What matters is the specific architecture of the system, not the word “digital” itself.

Why does the frequency range of the device matter?

The frequency range determines in which part of the RF spectrum a particular transmitter and receiver can operate. This directly affects the ability to find free and mutually compatible frequencies.

Two receivers of the same series may come in different bandwidth variants. If their ranges do not overlap, transmitters cannot be swapped freely, nor can the entire system be planned as a single common pool.

In larger productions, a wide tuning range provides more options for avoiding:

• local emissions,
• other wireless systems,
• interference,
• unfavorable parts of the band.

It is also important to remember that the availability of specific frequencies depends on the location and local regulations. Therefore, one should not choose a system solely based on the fact that it “operates in UHF.”

In practice, before the event, it is necessary to check, where the system will be used exactly and what RF devices will be operating next to it..

How does the RF environment affect the choice of system?

The RF environment includes all radio signals present at the event location. The more crowded the spectrum, the more important the capabilities of tuning, scanning, and frequency coordination become.

Interference can come from, among others:

• other wireless microphones,
• IEM systems,
• local radio and television broadcasts,
• devices operating in other shared bands,
• technical equipment located in the facility.

In a large system, it is not enough to find frequencies where "nothing is currently heard." It is also necessary to select channels so that the wireless devices themselves do not generate problematic intermodulation products.

That is why larger productions use spectrum scanning and software for frequency coordination.

Shure indicates that proper RF planning is needed in both analog and digital systems, as both can be susceptible to interference.

What is the difference between diversity and true diversity?

Diversity is a general method of increasing reception reliability by using two or more antennas or receiver paths. It aims to reduce the risk of dropout caused by multipath, which is a situation where waves reach the antennas via different paths and can cancel each other out.

However, the term "diversity" does not precisely describe how the system is constructed.

In solutions referred to as true diversity two antennas and two independent receiver sections are typically used, and the system selects or combines the more favorable signal. Shure distinguishes such a solution from simpler techniques that use one receiver section and antenna switching.

In practice, this means that when comparing systems, it is not enough to read the word "diversity" on the casing. It is worth checking, how the manufacturer exactly implements differential reception.

In critical concert and event applications, the architecture of the receiver can have a real impact on resistance to signal loss.

When is antenna distribution needed?

Antenna distribution is primarily needed when multiple receivers are to use a common pair of properly positioned antennas.

Without distribution, each receiver may require its own antennas. In a large rack, this creates many RF elements placed close together, often in an unfavorable position relative to the stage.

The distribution system allows:

• to use a common pair of antennas,
• to place them in a better location,
• to split the signal to multiple receivers,
• to limit the number of antennas at the rack.

Active distribution devices can also compensate for losses resulting from signal splitting. Shure describes distribution as a way to transmit two antenna paths to multiple receiving channels; example systems from the manufacturer split one pair of antennas to several receivers.

This does not mean that with two simple channels, it is always necessary to use an elaborate active system. However, the greater the number of receivers and the more demanding the infrastructure, the more sense centralized distribution makes.

How to select and position antennas?

The antenna must be compatible with the frequency range of the system and be located in a place that provides the best possible radio path between the transmitter and the receiver.

One of the basic principles is to maintain as good a line-of-sight, that is, radio visibility. It is not about the transmitter needing to be literally visible to the operator, but that there should be as few obstacles as possible between it and the antenna that attenuate or reflect RF.

Shure recommends, among other things, avoiding walls, large metal objects, and large numbers of people between the transmitter and the antenna, and – when possible – raising the antennas above the audience and other obstacles.

In practice, antennas are often positioned:

• near the stage,
• to the side of the stage,
• on an elevation,
• in a location that provides good coverage of the entire area of performer movement.

It is not always best to leave them behind the receivers in a rack standing under the stage.

One must also remember about RF cables. A coaxial cable attenuates the signal, and the loss increases with length and frequency. Therefore, a very long antenna run can negate the benefit of a good antenna position. Shure recommends using appropriate low-loss cables and considering their attenuation when designing the path.

The gain of an active antenna or booster should also not be set "to maximum." The goal is to compensate for actual losses, not to overload the RF input of the receiver.

How to plan a larger multi-channel system?

A large wireless system should be planned as a single whole including frequencies, receivers, antennas, distribution, power, and monitoring.

A practical workflow might look like this:

1. count all microphone and instrument channels;
2. add IEM and other RF devices;
3. check the tuning ranges of all devices;
4. perform an RF environment scan;
5. prepare frequency coordination;
6. configure receivers and transmitters;
7. plan antennas and distribution;
8. check RF levels throughout the work area;
9. conduct a movement test with transmitters.

With many channels, networking is also very important. Modern receivers can provide information about:

• RF quality,
• battery status,
• audio level,
• frequencies,
• alerts.

This allows the RF operator to monitor the entire system from one position instead of controlling each receiver individually.

The more channels there are, the more the wireless system becomes an RF infrastructure, and less a collection of individual microphones.

Microphones and IEMs operating during a single event

Wireless microphones and IEMs should be planned together, as both systems use RF and can operate in the same physical space.

In a wireless microphone, the transmitter is located with the performer, while the receiver is usually in the rack. In a classic IEM, the situation is reversed: the transmitter is with the monitor world or rack, and the receiver is with the musician.

This causes a different RF geometry.

IEM transmitters can operate with relatively high power near microphone receivers if the entire infrastructure has been poorly laid out. Therefore, IEM transmitting antennas and microphone receiving antennas should not be treated as random elements standing next to each other.

In many IEM systems, antenna combiners are also used. Shure indicates that when connecting multiple IEM transmitters, active combiners help reduce the level of unwanted intermodulation products compared to simply connecting transmitters.

The topic of monitoring is described in more detail in the article Floor monitors or IEM in-ear systems – what to choose for the stage?

The most important rule is: microphones and IEM should be in the same RF coordination.

How to choose a system for a concert, conference, and corporate event?

The same wireless system can work well in several applications, but the priorities are different.

At a concert the most important factor is resistance to dynamic stage conditions. A vocalist or instrumentalist can move across a large area, while IEM, communication systems, and other radio devices are operating nearby. The system must have appropriate RF stability and well planned antennas.

At a conference the number of channels and the ability to quickly manage the microphones of several speakers and panelists often matter more. A headset can provide a more stable speech level than a lavalier, but the final choice depends on the format of the event.

At a corporate event the system should be flexible. During one evening, a microphone for the host may be needed, several bodypacks during the presentation, handhelds for Q&A, and later a microphone for the vocalist.

Therefore, the system should not be selected solely for one point of the program. The selection and rental of wireless systems should consider the largest RF configuration that will occur during the entire event.

Summary

The selection of a wireless microphone starts with its application, but it does not end with the capsule and type of transmitter. It is necessary to determine the number of channels, RF environment, available frequency range, method of reception diversity, antenna positions, distribution, and cooperation with IEM.

For a simple event with one or two channels, the configuration can be very straightforward. For a dozen or several dozen systems, a common RF design is needed, including spectrum scanning, frequency coordination, antennas, and monitoring of the operation of devices.

The most important practical conclusion is simple: the reliability of the wireless system depends on the entire RF path, not just on the quality of the transmitter and receiver. A well-chosen capsule will not help if the antenna is in the wrong place or if the system operates on poorly coordinated frequencies.

Frequently Asked Questions