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The Freedom of a Wireless System
A wireless microphone system gives you the freedom to move about the platform without the restrictions of a cable. Wireless microphone and instrument systems offer this mobility while providing professional audio quality. When choosing the right wireless system for your needs, there are a number of factors to consider, both subjective and objective. This guide is designed to clear up some of the mysteries behind the operating principles of wireless systems. As always, feel free to call 1-800-222-4700 for answers to all your wireless system questions.
What Goes Into a Wireless System?
A wireless microphone system consists of a microphone, a miniature radio transmitter, and a radio receiver. The transmitter is like a tiny FM radio station broadcasting the performer’s signal while the wireless receiver is like an FM tuner or home radio. The only difference is that the receiver is designed so that it is only able to pick up the signal from one particular matching transmitter. In addition, wireless transmitters are battery operated so that they are completely portable.
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There are two basic types of wireless microphone transmitters: handheld and bodypack. Handheld transmitters look like vocal microphones and include the microphone element, transmitter and battery in one package. Bodypack transmitters are small boxes that can go into a pocket, be worn on the belt, or be concealed under clothing. They include the transmitter, battery, and a small microphone connector. Bodypack transmitters are generally used with miniature lavalier microphones that attach to clothing, or with headworn microphones. Bodypack transmitters can also be used for musical instruments.
VHF and UHF
| For a simple single-user setup, an economical VHF system works fine. |
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Wireless mic systems generally operate in several frequency bands, which include the VHF TV channels 7 through 13, or UHF TV channels 14 through 69. The demand for more spectrum usage is increasing while the available spectrum for wireless microphones is decreasing. This means you must choose your wireless system carefully to avoid interference from outside signals. Your Sweetwater Sales Engineer can help you select appropriate frequencies.
It's generally accepted that a UHF system has greater range due to higher power output, and is less susceptible to television interference. However, there are other factors to consider. Higher output power from the transmitter helps overcome dropout problems and can increase (but does not guarantee) operating range, but the sacrifice is often shorter battery life. Most high-quality VHF transmitters offer a reasonable operating range and economical battery life.
A Diversity Receiver Ensures Dropout-free Performance
The term "diversity" is one of the most widely misunderstood concepts of wireless systems. As it applies to wireless microphone receivers, the term simply refers to the use of two antennas to receive a microphone’s signal to eliminate "dropouts.” Dropouts occur when there is interference between the transmitter and receiver antennas, often due to a physical obstruction such as a wall or balcony. Sometimes simply moving around the stage – or parishioners who move about in the auditorium - can result in dropouts caused by reflected radio waves. Moving the receiver antenna to a different location can often reduce or eliminate dropouts. When setting up a wireless system it’s always a good idea to conduct a “walk test” with the microphone to locate dropout-prone areas.
With a diversity system two antennas, each in a different position, pick up the transmitter’s signal. The receiver looks at the signal coming in from the each antenna, and determines which one is the stronger. It then switches to that stronger signal. In a “true diversity” system, there are two independent receivers that perform the same function. A typical diversity receiver is the Shure ULXS4. While this provides the most reliable operation, a diversity system isn’t always necessary. In a setting where there are no obstructions between the transmitter and receiver, and only one wireless mic is being used, it may well be cost effective to choose a VHF non-diversity system.
Wireless Setup Basics
Setting up a wireless mic involves a few more steps than just plugging in and turning up. But, after you've done it a few times it will become an easy habit. This information applies to wireless systems in general. We always recommend that you follow the instructions found in your owner's manual.
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Regardless of what type of transmitter you have, always be sure you start with a fresh battery. Battery life varies from system to system; check your manual. A good rule of thumb - If your battery has served more than half the listed life, replace it. |
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Make certain your transmitter is off. |
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Turn on your receiver. |
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If your system has Automatic Frequency Selection, press the receiver's "Select" button. It will scan and locate a suitable frequency. |
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Temporarily turn down the receiver's volume or level control. |
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Turn on your transmitter. |
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If your system has Automatic Transmitter Setup, press the transmitter's "Sync" button. It will lock on to the receiver's selected frequency. Check the receiver's LED or meter to confirm that it's picking up the transmitter. Turn the receiver's volume control up to a "normal" level. |
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Now adjust the transmitter's audio gain. This is the key to getting a good sound and good levels! You might need a screwdriver for this. Sing or speak loudly into the mic and increase the gain slowly until the receiver's "RF Level" or meter occasionally flashes to indicate a peak during the very loudest moments. |
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Do a walk-around through the performance area while observing the receiver's "Power" LED or RF meter. It should indicate sufficient reception in all areas of coverage. If you experience a dropout, reposition the receiver or its antenna for better reception. |
Simply stated, setting the proper input gain is the most important adjustment on a wireless microphone system. Set too low, the signal-to-noise ratio of the system will suffer. Set too high, severe distortion and/or compression of the dynamic range will occur. Adjusting the transmitter input gain is very much like setting the record level on an analog tape recorder. It is important to consider the features and controls offered on any wireless transmitter that enable accurate gain adjustment.
The transmitter-to-receiver distance has a major effect on the signal-to-noise ratio of a wireless system. As the transmitter moves farther away from the receiver, the overall signal-to-noise ratio grows worse as the transmitter signal gets weaker. When the system gets near the limit of its operating range, dropouts will become more frequent and a buildup of steady background noise (hiss) may be audible.
Which Wireless Microphone is Right for Me?
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Wireless Lavalier/Headworn System:
There is no doubt that wireless lavalier microphones have just about become the standard for miking the worship leader. That's not to say, however, that a reliable wired lectern microphone doesn't have certain advantages. Consider the following:
1 Does the worship leader move around the pulpit? If the answer is "yes", you'll probably want to invest in wireless lavalier mic system such as the Sennheiser EW 122 G2. Lavalier mics are great because they're completely inconspicuous and won't interfere with the sight line of the congregation. A wireless system outfitted with a beltpack transmitter allows the worship leader to move freely about the room and congregation. Perhaps the best combination of sound quality and mobility comes via headworn systems such as the Countryman E6 Earset microphone. The E6 is virtually invisible and moves with the speaker’s head. Therefore sound is always clear and consistent.
2 Does the worship leader stay in one place or will other speakers be stepping up to the mic? In that case, a wired lavalier system or lectern microphones might be a better choice. Generally speaking, it's better to use a single lectern mic rather than two to ensure a more consistent tone.
3 Cardioid or Omnidirectional? The speaker's style will influence the choice you make in microphone polar patterns. Lavalier, lectern and handheld mics come in both types. While conventional wisdom suggests that unidirectional or cardioid mics such as the Sennheiser ME 4 may offer more stable performance in live applications, you'll want to experiment. If the worship leader moves his or her head from side to side, his or her voice may move in and out of the narrower pick-up pattern of a cardioid mic. The result will be less audibility when the speaker’s head is turned away from the mic. An example of an omnidirectional lavalier is the Sennheiser ME 2. While the omni may offer a slightly more true-to-life sound it also presents greater feedback challenges, particularly when in close proximity to other active lavalier mics.
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Handheld Microphone w/ Built-in Transmitter:
This is the mic for a worship leader or vocalist who needs mobility. It can provide much greater feedback rejection and allow higher volume than a lavalier. It’s perfect for situations in which a mic will be passed from person to person. A handheld wireless mic such as the affordable Sennheiser freePORT Vocal Set may well be the ticket. Models such as the Shure ULX2/Beta58 use the same capsules as popular vocal mics. |
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Acoustic Instrument Mics:
There are certain acoustic instruments that may have to compete for volume with amplified guitars, keyboards, and basses, but don’t lend themselves easily to stationary miking. For instruments such as trumpet, trombone, and sax, the Samson Airline 77 Wind Instrument System has an integrated transmitter, eliminating the need for a bodypack, and features a mic that clips onto the bell of the instrument. For flautists, the Audix ADX10-FL miniature condenser mic mounts on the flute head joint. The advantage of these mics is the ability to play while eliminating obtrusive mics, stands, and messy cable runs. |
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Guitar and Bass Wireless Systems:
Guitar and bass players were among the first to go wireless onstage, with freedom of movement and less risk of tripping over cables being the most obvious advantages. The Audio-Technica ATW-3110 system features a compact transmitter that stays in place no matter how much a musician may move about. The Samson Airline Wireless Guitar system eliminates the bodypack and comes with a connector designed to fit guitar and bass with either Gibson-style or Fender-style output jacks. |
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