AKG Acoustics WMS 4000 Feedback, Frequency Management, Frequency Modulation, Frequency Range

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AKG WMS GLOSSARY

GLOSSARY

DEFINITIONS FROM A TO Z

Feedback

When a microphone picks up amplified sound from a loudspeaker this signal will be reamplified, picked up again, etc., until the commonly known shrill howling (some- times a lower midrange rumbling) sets in.

In small rooms, feedback is usually caused by reflections. In this case, acoustic treat- ment of the walls should help. On stages with correctly set up FOH speakers it is the monitor speakers that may cause feedback. A very good hypercardioid microphone (e.g. a D 3900) may sometimes provide a few extra dB's of gain-before-feedback. Place the monitors slightly off-axis (135-) where the microphone is least sensitive.

Frequency Management

Organization of frequency resources.

Frequency Modulation

A technology that alters (modulates) carrier frequencies to transmit information.

Frequency Range

The frequency range of a microphone is usually stated as the upper and lower fre- quency limits within which the microphone delivers a useful output signal.

Frequency Response

Microphones are not equally sensitive to all notes. The frequency response indicates the relationship between sensitivity and pitch. The 0-dB reference being the output voltage at 1 kHz, the frequency response is measured at constant sound pressure level, from about 20 Hz (lowest note) to 20 kHz (above the upper limit of human hearing).

Hum Sensitivity

Magnetic fields from amplifiers, long power cables, and lighting systems in particular may induce hum in microphones. A micro- phone's hum sensitivity gives an indication of how susceptible it is to this kind of inter- ference. Values are 3 µV/5 µT for dynamic microphones with hum suppression coil, 30 µV/5 µT for dynamics with no suppres- sion coil (D 90, D 95, D 190), and up to 10 µV/5 µT for condenser microphones.

In practice, though, it is the microphone cables, most of all unbalanced ones, and mixer inputs, that are most likely to pick up hum.

Impedance

Frequency dependent AC resistance of a microphone. Always quoted at 1 kHz the actual impedance at other frequencies may differ slightly from this reference value. Also known as “source impedance”.

Intercept Point

The Intercept Point (IP) provides a measu- re for an amplifier's resistance to intermo-

dulation distortion. IP 3, for example, is the reciprocal value of the third-order coef- ficient of an amplifier's nonlinear transmis- sion polynomial.

Interference

Disturbance in transmission caused by extraneous signals.

Intermodulation

A nonlinear (multiplicative) combination of signals with different carrier frequencies that will produce completely new frequen- cies, called intermodulation products.

Limiter

Electronic circuit that prevents subsequent circuits being overloaded by excessive sig- nal levels that would also cause distortion.

Line Microphone

The directivity factor of conventional unidi- rectional microphones is limited by the laws of physics. This can be overcome by installing a slotted tube in front of the dia- phragm (“interference tube”). Off-axis sounds are canceled through interference, which results in an ultradirectional polar pattern.

Matching

Microphones should operate in an open cir- cuit. This is the case if the input impe- dance of the preamplifier or mixer is at least 2 to 5 times as high as the microphone's rated impedance. The appropriate value is quoted in the specifications of each micro- phone as “recommended load impedance”.

Maximum SPL

The highest sound pressure level (loud- ness) a microphone can handle without introducing more than a specified amount of “Total Harmonic Distortion” (1 %), in other words, without distorting the signal. Usually measured at 1 kHz, except for the C 460 B ULS Series where it is quoted from 30 Hz to 20 kHz.

Mechanical Noise

See “Vibrational Noise”.

Memory Effect

The loss of capacity which occurs in nickel- cadmium storage batteries if they are not completely discharged prior to recharging.

Modulation/demodulation

A sine-wave carrier starting at a time of minus infinity and ending at a time of plus infinity contains no information. However, any change in amplitude or frequency at any time (e.g., a pulse-like change) adds information to the carrier.

This process is called “modulation”. The process by which a receiver detects and extracts this information from the carrier is

called “demodulation”.

Multichannel System

A wireless microphone system that allows several radio microphones to be operated simultaneously in the same room.

Noise Burst

Brief disruption of the desired signal by noise from a transient interference source (e.g., ignition spark).

Noise skirt

An ideal carrier spectrum would be a line. As the carrier is modulated, the noise inhe- rent in the switching signals makes the tran- sients look ragged. This raggedness ultima- tely frequency-modulates the carrier with noise. Once that happens, the carrier spec- trum is no longer a line but a noise spec- trum that tapers off to either side of the wanted frequency, which is why this part of the spectrum is called a “noise skirt”.

Phantom Power

to IEC 2681 5/DIN 45596

Condenser microphones require an opera- ting voltage. It can be fed to the micro- phone either by a-b powering or phantom powering. In a-b powering, the operating voltage is fed to the balanced audio wires without using the shield. a-b powering is incompatible with dynamic microphones since the operating voltage would flow through the moving coil and destroy it.

In phantom powering, the negative terminal is connected to the cable shield and the positive terminal is split via decoupling resistors to the balanced audio wires. Since both audio wires carry the same potential, no current will flow through the coil of a dynamic microphone so there is no risk of destroying it even if the phantom power is accidentally left on.

When adding phantom power to a single ended (grounded) input or an input with no front-end transformer, either capacitors or an optional transformer need to be wired into the audio lines as shown below, to pre- vent leakage currents from entering the input stage.

Polarity

If you use more than one microphone for a recording, they should be of the same pola- rity. This means that if the diaphragms move in the same direction, the output vol- tages of all microphones should have the same polarity. If they don't there will be sig- nal cancellation effects causing sound coloration – particularly in the bass range – as soon as you mix the microphone output signals together.

Polar Pattern

The “polar pattern” of a microphone indi-

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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 element444 L 417 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 MicroMicsAccessories GB 40 Guitarbug for Guitar and BassJack plug Guitar system in a bag FlexJack for all electric guitar modelsFlexJack for all electric bass models HOW Multichannel Technology Works WMS frequency band with TV transmitter IntermodulationUse before each performance Automatic frequency setup Shadow loss Multipath transmissionTroubleshooting Hints Problem no sound microphone does not functionProblem 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 InterceptMicrophone a carrier frequency Spectrum analyzer traceFrequencies 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 example Stadium theater, opera house exampleShort antenna cable runs Drawbacks Speech Vocals Guitar/Bass Instruments Live soundTV studio Theater CU 4000/BP HUB 4000 Network concentrator SRA 1 Passive wideband dirctional antennaRA 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 outputs BNC antenna inputsDaisy-chaining outputs AKG WMS PS Antennas Tailored to Every Situation Cabling example/cable lengthsSelecting 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 PSUExample 10-CHANNEL System for Tour Sound 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/PTALL the Specs AT a Glance SystemMP 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.