AKG Acoustics Understanding Multichannel Wireless Performance with WMS 4000 Technology

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AKG WMS MULTICHANNEL TECHNOLOGY

HOW MULTICHANNEL TECHNOLOGY WORKS

FREQUENCY MANAGEMENT, INTERFERENCE, AND PRACTICAL REMEDIES

Interference due to intermodulation can occur as soon as a radio-frequency circuit consisting of semiconductors or ferrites – like that of a WMS receiver – handles several RF signals at different frequencies. The number of disturbing frequencies (intermodulation products) increa- ses exponentially wherever several radio links (frequencies) are used simultaneously. This laws of physics have the biggest impact when several radio microphones are used at the same time. The innumerable new frequencies genera- ted by the combination, addition and subtrac- tion of the desired frequencies cause additional interference. Expert management of the fre- quencies of all radio sources designed to be used simultaneously is therefore absolutely essential for the problem-free operation of a multichannel wireless system.

Incorrect positioning of the antennas and recei- ver is just as frequently a source of undesirable interference. It is essential to ensure a mini- mum distance of 5 feet (1.5 m) from large metal objects such as lighting gantries and stage decorations (especially wire mesh). You should also avoid placing antennas in wall niches to prevent shadowing. Radio signals reflected or shadowed by walls, ceilings or metal structures also weaken the useful signal, thus resulting in improper functioning of the

radio equipment (see WMS 40 illustration on page 6/7). The interference from electrical appliances that cause electrosmog (such as computers and lighting equipment) can be par- ticularly disturbing during deep fades. During a deep fade that changes only slowly, a tone code squelch prevents unwanted noise from lasting too long.

On the other hand, a conventional muting cir- cuit is unable to differentiate between “friend” (the right frequency) and “foe” (unwanted sig- nals). If the level of interference is too high, it may interrupt the audio path during noisy deep fades. Most receivers use both types of circuit: a fast muting circuit to eliminate short bursts of noise, and a tone code squelch to reject persis- tent noise. Since both types of circuit act like a hard gate on the audio signal, there will always be some residual switching noise.

To ensure problem-free operation, always ob- serve the following basic rules when setting up a multichannel wireless system as opposed to a single channel application. Always position the receiving antennas within the far-near differ- ence range (see page 45). Nevertheless, make sure there is always an unobstructed line of sight between the transmitter and receiver during the performance. Also, the better the

audio signal fed to the transmitter and the high- er the signal/noise ratio of the transmitter and receiver, the better your wireless system will work. Basically you should always set the trans- mitter audio input gain first. The signal-to-noise ratio is the ratio between the amplitude of the wanted signal and the noise amplitude; it is a logarithmic expression for the purity of a signal. With radio transmission, the signal/noise ratio depends on the amplitude of the audio signal. The stronger the audio signal, the better the sig- nal-to-noise ratio. This is why it is always a good idea to make sure not to set the audio input gain of the transmitter too low.

In order to enhance the signal/noise ratio, the audio signal passes through a pre-emphasis cir- cuit in the transmitter and a corresponding de- emphasis circuit in the receiver. The amplitude of the signal is not evenly distributed over the frequency spectrum. Higher frequencies have a lower amplitude than lower frequencies, resul- ting in a lower signal-to-noise ratio for higher frequencies than for lower ones. FM demodula- tion generates more high-frequency noise. The pre-emphasis circuit boosts higher frequencies ahead of the radio link, whilst the de-emphasis circuit in the receiver attenuates them by a cor- responding amount.

Automatic frequency setup

During concerts and other performances, a number of applian- ces emit electromagnetic waves that may disrupt your transmis- sion channels (outside interference). Thanks to the “Environment Scan” function, AKG wireless systems are able to localize such “jammers”, switching to suitable interference-free frequencies instead.

In other words, the system automatically searches for gaps in the fre-quency spectrum – that is, frequencies where no interfe- rence is de-tected – occupying them with its own carrier fre- quencies.

Important: Run Environment Scan during the soundcheck and note the results. Do another test shortly before the performance, as there will almost certainly be new sources of interference, such as television and radio transmitters, or mobile phones in the audience. This gives you time to correct any problems that may have arisen.

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Contents Wireless Page Wireless Technology for the Future Pioneer in Acoustics for Over 50 Years120 DYN How it all started …Die DYN Series Founders Dr. Rudolf Görike and Ing. Ernst PlessEarly products 12 a180 Company namePeter Wolf BreakthroughExpansion course Rock me AmadeusWMS AKG expands its activities in the wireless marketTurning point New research centerJust like a radio set HOW Radio Signals are TransmittedCase for wireless mics Radio waves instead of cablesSignal propagation Positioning the receiverRule no WavelengthInterference BandwidthFrequency Modulation FM Example of AKG WMS 40 carrier frequenciesModular Solutions to Meet Individual Requirements Head-worn microphone for extreme Clip-on or head-worn microphoneFor presenters Activities like aerobics and sportsHandheld Mics for Lead and Backing Vocals Microphone cleaning and maintenance On/off switchVolume Angle of incidenceHEAD-WORN Mics for Lead and Backing Vocals PT 40 Portable transmitter Mini XLR connectorRear panel and battery compartment Flexible antennaAF LEDs SR 40 diversity Receiver ON/OFF switchAntennas Alternative receivers Diversity LEDsSO 40 snapon transmitter Release button Battery compartmentXLR connector Color codeXLR connector pin 2 hot Setting the squelch thresholdBattery charging made easy TM 40 Transmitter module Status LED3700M 3800M Wireless and supremely flexibleOn/Off switch AF LEDs 880MMicrophone MP 40 Micropen for PresentersCable compartment Color code pen clipDetachable microphone MP 40 micropen in handheld modePR 40 Portable receiver ON/OFF switch Put it in your pocket …With C 444 L head-worn or C 417 L lavalier microphone More Goodies for PresentersPT 40 Bodypack transmitter With proven D 880M microphone element417 L 444 LAvoiding feedback Wireless Systems for Maximum Mobility Training communicationsPR 40 Portable receiver PT 40 careAKG WMS 40 UHF for Instruments Radio Links for Portable InstrumentsInstrument MicroMics Connecting to microphone or line inputsMicroMic C 411 L pickup Instrument MicroMic Instrument MicroMicsGB 40 Guitarbug for Guitar and Bass AccessoriesJack plug FlexJack for all electric guitar models Guitar system in a bagFlexJack for all electric bass models HOW Multichannel Technology Works Intermodulation WMS frequency band with TV transmitterUse before each performance Automatic frequency setup Shadow loss Multipath transmissionProblem no sound microphone does not function Troubleshooting HintsProblem poor audio Modular Solutions for Custom Reqirements Backlit LC display SR 400 Receiver On/Off switch Recessed level controlStatus LEDs Metal caseRange of accessories for complex applications Auto setupRehearsal mode Infrared transmissionInfrared sensor On-Mute/Program-Off switchExtremely rugged spring steel mesh grill HT 400 Handheld transmitter DisplayBattery status display Frequency preset LCD display Rugged mini XLR connectorJack for external mute switch Frequency in MHz Low battery capacity warningLocking DC jack Input jack for a local or central power supply e.g., PSUUser Friendly Quick Charger Integrated charging contacts for direct chargingRA 4000 B Omnidirectional wideband booster antenna PSU 4000 Central power supply unitAB 4000 Antenna booster HPA 4000 Headphone amplifierSetting UP Multichannel Systems IP 3 InterceptSpectrum analyzer trace Microphone a carrier frequencyFrequencies Frequency Management a good idea for any multichannel system Stage a Stage B Here is a proven way to add clean frequenciesFar-near difference Band I + 0,15Modular Solutions for Professional Requirements Skin Fat SELECTING, Placing and Using AntennasSignal loss caused by the audience Muscle CartilageCable type Impedance SELECTING, PLACING, and Using AntennasCable position a Cable position B GageStadium theater, opera house example Stadium exampleShort antenna cable runs Drawbacks Live sound Speech Vocals Guitar/Bass InstrumentsTV studio Theater SRA 1 Passive wideband dirctional antenna CU 4000/BP HUB 4000 Network concentratorRA 4000 B Automatic gain setting Battery status readoutFrequency presets Battery compartment Jog switchInscribable color code element Magnesium body Jack for remote Mute switchSilent Mode setting Hidden pilot toneProgrammable status display CUTTING-EDGE True Diversity ReceiverBacklit display Half-rack 19 all-metal case SR 4000 ReceiverEnvironment Scan Battery life displayEnvironment Scan and Rehearsal Mode Professional XLR and jack outputsCU 4000 Charging unit Lockable DC jack Intelligent WAY to Power WMS 4000 TransmittersCharging status display LED Recovery key and LED Such as a PSUInternal RAM Integrated temperature sensorCU 4000 Charging unit in a flight case Data interface to transmitter electronicsBNC antenna inputs BNC antenna outputsDaisy-chaining outputs AKG WMS PS Cabling example/cable lengths Antennas Tailored to Every SituationSelecting and placing antennas SRA 2B Active wideband directional antenna ASU 4000 Remote powerd adapter for antennasSRA 1 Passive wideband directional antenna ZAPD-21 Antenna combinerAs RF levels on site. This makes it incredibly Standard PC accessories. This allows you toLink Between the WMS 4000 and a PC Network Example WMS 4000/PC networkYour Computer AS a WMS 4000 Control Center You can even set up the basic parametersGet a Cup Setup Mode Moving PC Rehearsal Mode Ensures maximum operating reliabilityAKG WMS 4000 Power Supply Line input jacks, DC input lockable Jog control Recommended headphonesMonitoring Without a Mixer StudioSpecification Amount Description SeminarsRA 4000 B PSUTour Sound Example 10-CHANNEL System for Tour SoundAmount Description AKG WMS Practical Examples Example 16-CHANNEL System for Mobile USE Vienna KonzerthausGala Musical Couples, August WMS 4000 WiringWMS 4000 mobile rack Detailed system layout is shown on the following pagesWMS 4000 16-CHANNEL Setup AKG WMS Practical Examples Example 46-CHANNEL System for AN Opera House High-tech for pure enjoymentStage Channels Channels WMS 4000 1-CHANNEL Setup SpecificationAKG WMS Practical Examples Banjo GuitarViolin and viola See guitar. top rightTubas SaxophoneClarinet TromboneSound systems AV/sound companyBars and clubs Meeting and social roomsAKG Wireless Systems AT a Glance Microtools HT/PTSystem ALL the Specs AT a GlanceMP 40 micropen PR 40 diversity Mounting kit, 2 antennasDefinitions from a to Z Directional Antenna Electromagnetic Wave SpectrumDistortion Environment DiversityFrequency Management Phantom PowerFeedback Frequency ModulationPop Noise Hypercardioid Ultra-directionalCardioid Pressure Gradient MicrophoneReflection Signal LossSignal-to-noise S/N Ratio Remote AntennaIndex Selected KeywordsAppendix Appendix Appendix Appendix Appendix Page AKG ACOUSTICS, U.S
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WMS 40, WMS 400, WMS 4000 specifications

AKG Acoustics has long been recognized as a premier brand in the professional audio industry, particularly in the realm of wireless microphone systems. Among its celebrated offerings, the WMS 4000, WMS 400, and WMS 40 series stand out for their advanced technology and robust performance, catering to a range of applications from live performances to studio recordings.

Starting with the WMS 4000, this system is engineered for versatility and reliability. It features a sophisticated transmission diversity system that minimizes dropouts and ensures clear audio quality. The WMS 4000 offers an extensive frequency range, accommodating diverse environments and frequencies. A standout feature is its digital pilot tone, which automatically mutes the transmitter when it is switched off, effectively preventing unwanted noise during transitions. With a range of up to 300 meters, the WMS 4000 is ideal for large venues, allowing performers ample space to move without compromising sound quality.

Next, the WMS 400 series maintains the high standards set by its predecessor while providing a more accessible option for mid-level performers. It combines ease of use with quality audio performance, boasting a user-friendly interface that simplifies setup and operation. The WMS 400 employs an efficient frequency management system, which automatically scans the environment to select the best frequencies available, ensuring optimal performance with minimal interference. The system also features a rugged metal chassis, enhancing durability for live applications.

The WMS 40 series serves as an entry-level solution, perfect for beginners and small venues. It is lightweight and features a straightforward design, making it easy to operate for users without extensive technical knowledge. One of its most notable characteristics is its plug-and-play functionality, allowing for quick setup without complicated configurations. The WMS 40 series also offers excellent sound quality through its crystal-clear audio transmission and robust reception, making it a popular choice for schools, theaters, and small events.

All of these systems benefit from AKG's heritage in sound engineering, incorporating advanced audio processing technologies that ensure superior sound fidelity. They also come with a variety of microphone options, including handheld, lavalier, and headworn microphones, providing flexibility to meet different performance needs. Whether for a professional stage or an intimate setting, the AKG WMS series delivers outstanding performance, reliability, and user-friendly features that cater to a wide range of audio applications.