Technology Showcase: Audioconferencing Systems
Apr 1, 2007 12:00 PM, By Bennett Liles
Careful installation is key to meeting the challenges of conferencing in medium to large venues.
High-profile conferences in medium to large venues are technically challenging — even when the acoustics are good, and the sound system is working. Once you've gotten more than a dozen speaking participants involved, manual mixing is just too much to handle. This is particularly true with a free-form situation, in which anyone can talk at any time. You can't simply put up all the microphones and sit back. Therefore, much of the complexity of audioconferencing systems, and their cost, comes from the mechanisms of automatic microphone selection for participants who have no expertise in handling such equipment. In fact, along with automatic mixing, some audioconferencing controllers have a selector that limits the number of microphones that can be on at any time.
Adding to the complexity is the fact that, in many cases, a conferencing system is installed as an upgrade in an older facility that does not have modern acoustic treatment or design. Bad acoustics can make a good audio system sound bad and serve as an insurmountable challenge to even the best-designed and -installed conferencing system. As the ratio of direct-to-reflected sound decreases, the effectiveness of echo cancellation in the conference mixer will deteriorate. The full effect of bad acoustics and improper configuration will be even more noticeable on a broadcast or multipoint conference feed than it is in the room. The good news is that these products have gotten smarter and more capable in recent years, to the point that if a system is competently selected and installed, it can function adequately in all but the most dismal acoustic environments.
Key points in the setup of an audioconferencing system are positioning the microphones close enough to the participants for strong direct sound pickup without breath popping, setting the threshold levels on the mixer noise gates so that conversation is properly mixed without “upcutting,” or chopping off the first syllable of speech, and keeping the microphones away from sound emitters such as sound system speakers or HVAC equipment. Even the most sophisticated electronic noise suppression system is no substitute for a noise-free acoustic environment, but when used, noise suppression should be transparent so that its effect is noticed only after it is turned off.
Only the best-quality cables should be used, and any with damaged shields or broken ground pins should be eliminated. A tiny, but steady, background hum can be ignored by listeners, but electrical noise and hum, picked up in microphone cables and amplified, will become quite obnoxious when the action of a compressor or noise gate brings it up and down with the speakers’ voices.
With the range of options presently available, a good fit can be found for any conferencing venue and format. Here is a survey of key systems offered in the current marketplace.
AKG Acoustics offers the CS2 as a modular and cascadable discussion-reinforcement system with a choice of microphone polar patterns through interchangeable capsules, goosenecks of various lengths, and a 1RU CS2 BU base unit with DIN-type expansion ports. Along with automatic mixing, or microphone selection, the CS2 features number of microphones (NOM) limit selection. Included are a master output level control, headphone jack with level control, and speaker output level. On the input side are master microphone, line, and auxiliary input level controls. An operation mode selector allows for a choice of microphone operation between voice activation and push-to-talk buttons on the individual microphone stations.
A choice of long- or short-stem gooseneck microphones, a local speaker level control knob, 3.5mm headphone jack, and a push-to-talk button can be connected to the delegate stations. The chairman station is identical to the delegate units with the addition of a priority override control. Adjustable functions include voice-activation hold time and on/off, NOM enable/disable, priority level, and adjustable compression. The MSRP for the CS2 BU/20 base unit for up to 40 mic stations is $3,165. Each chairman station is $893, and each delegate station is $832.
The Envoy digital discussion system from Auditel can be used in a portable, seat-arm, or flush-mounted configuration for up to 250 delegates. Each microphone station includes three-way voting and request-to-speak buttons, and a yellow “wind-it-up” flashing light activated by a speech timer. The voting buttons can also be used for individual gain adjustments.
The stations are connected by a single loop-through cable and may be controlled with a pushbutton console or with a PC running Auditel's Windows-compatible software, which also provides camera control for fully automated image projection. The microphone stations are available in tabletop portable, seat-arm mount, and surface flush-mount configurations.
The Beyerdynamic MCS-D 200 is a digital conferencing and interpreter system featuring MultiSession capability, in which one large conference can break up into several smaller ones with independent conference sound capability, and then return to one large system without the need to change any cabling.
The system consists of the MCS-D 200 control unit, MCS-D 202 interpreter station, MCS-D 2073 microphone station, and the MCS-D 2074 service microphone station. A single control unit can control up to 1,400 microphone stations, and its integral power supply can run up to 15 stations. Through the iCNS software, the NetRateBus can provide up to 54 audio channels with functions including private calling between microphone stations. The MCS-D 202 interpreter station features selectable A/B output and configurable access to the various audio channels. The 10-button microphone stations can be configured as chairman or delegate stations, and include a voting function.
The CDS200 II congress data system from Brahler provides a central control unit that can control up to 1,000 microphone stations and 4,000 voting units with centralized or decentralized (delegate) manual microphone switching. The DPS202 central control unit can operate the system in a standalone configuration or in conjunction with a computer for touchscreen, mouse, or keyboard control. Computer control enables electronic station labeling, ChipCard authorization, voting, and camera monitoring features. In addition to five voting keys, the DC9 delegate unit has a local speaker, information display, and illuminated microphone key. The delegate stations are also available in a flush-mount version with a variety of colors for permanent installations and can operate in various preset modes.
ClearOne's new Converge Pro line of audioconferencing platforms is headed up by the Converge Pro 880, which features eight mic/line inputs, four line inputs, 12 outputs, acoustic echo cancellation, and noise cancellation on each mic input, as well as drag-and-drop configuration software with an event scheduler.
The units are linkable for expanded capacity and include Ethernet and USB connections for remote management through SNMP and HTML. ALC and AGC circuits maintain steady audio levels, while mic channels can be gated in groups and sorted into 32 configuration presets. Single commands can execute up to 255 macros to automate configuration and operational changes. High-pass, low-pass, PEQ, and notch filters are also configurable. The Converge Pro line includes the Converge Pro 840T, Converge Pro 8i, and the Converge Pro TH20 telephone hybrid.
For multilingual meetings, the DCS 6000 digital conference system from Danish Interpretation Systems provides eight floor channels and 31 interpreted channels. The 6010 central unit features an integral power supply for all stations, and connects to them over DCS-LAN with Cat-5 cable. The front panel includes an alphanumeric LCD display showing mode, language, and system settings.
External PC control connections are available, and the system will interface with AMX and Crestron control. The microphone stations come with either fixed gooseneck mics or XLR connectors for other panel-mounted mics. Each unit includes a brightly illuminated light ring for identification of the unit in use. The system also offers the CM6060F and DM6060F chairman and delegate flush-mount microphone stations with a channel selector. All mic stations have an on/off pushbutton, a mic-on LED indicator, and a mic request in queue indicator light.
The Dwcs 2.4 from IRP Professional Sound Products is a digital wireless system operating on a carrier in the 2.4GHz band and consisting of chair and delegate microphone stations, the base receiver/processor, and the remotely mounted antenna system. Packetized digital audio provides 1mW transmission, with 1024-bit encoding to prevent interference and unauthorized reception. Rechargeable NiMH batteries in each unit allow eight to 10 hours of transmission time, with up to 8,000 stations in one system.
Chairman stations have delegate microphone override with a priority button, and any conference can be centrally administered with a PC running the Windows-based dwcs24Net administration software and interfaced with Crestron or AMX control. The base unit's four audio outputs can interface directly with an automatic mixer. The administrator can activate up to four microphones simultaneously based on stations sending requests to talk.
Listen Technologies markets the CCS 800 100-person discussion system as a powerful product in a compact form. The system consists of 98 LBB3330/00 delegate units, two LBB3331/00 chairman units, an LBB3310/10 control and power supply unit (CPSU) with feedback suppression, 10 33ft. lengths of station connection cable, and one LA210 multi-CPSU interface.
The delegate unit has a local speaker and two 3.5mm headphone jacks with volume control and an illuminated ring to indicate an active mic. All delegate units have seven-pin circular loop-through connectors for daisy-chaining the connection cable. In addition to all the delegate functions, the chairman unit features a priority button and delegate mic muting. The control and power supply unit allows four microphone operational modes and a test mode, and it can directly connect up to 50 microphones.
Media Vision USA has an interesting entry with its CloseTalk wireless infrared conference system, which features an unlimited number of stations running up to 10 hours per battery change in conference or 20 hours in listen-only. Each station includes a gooseneck microphone with variable-length stem, local speaker with volume control, speak request key, power/reply key, and headphone jack. The ceiling-mounted infrared transceivers can be surface- or flush-mounted to cover any size room.
The system's line-of-sight, IR-based wireless communication combines cable-free flexibility with the discussion security of a hard-wired system. PC software enables central control, voting, and delegate roll calls. The central control unit offers queue handling for up to 256 participants, line-in and telephone-in controls, chairman control functions, and a new videoconferencing camera-control capability.
The SDC 8200 digital conference system from Sennheiser combines discrete text messaging, software configuration, camera control, and interpreter functions with 10 conference modes for up to 1,024 participants.
The SDC 8200D delegate unit features a gooseneck microphone, integrated speaker, two headphone jacks with volume control, mic key, request-to-speak button, and voting keys. The SDC 8200DV adds smart-card voting, tallying, and text messaging. Each unit has two RJ-45s, enabling it to be daisy-chained on Cat-5. The SDC 8200C chairman unit includes mic control over the other stations. Other stations add 2-channel monitoring for multi-language events.
The SDC 8200CU/CU-M central unit provides balanced audio inputs and outputs, sub-D aux outs, serial PC interfaces for configuration with SDC 8200SYS software. This enables seating name assignments, conference configuration, vote tabulation and display, microphone management, and other functions.
When a site requires a conference system to be brought in for particular occasions, the Shure ConferenceOne discussion system provides several sophisticated features normally found in permanent installations. The SCM410 automixer can be linked to add wireless microphones to the system, and a media playback unit such as a CD player can be connected. Phantom power is available for adding external condenser mics.
The system can be fed into any existing PA system or can provide its own PA function with the internal speakers on the microphone stations. An AEC/telco interface with a six-pin block connector allows multi-point conferencing. Daisy-chain layout with Neutrik MiniCon connectors simplifies setup of chairman and delegate units, each of which has a telescoping, foldout Microflex gooseneck microphone. Shure IntelliMix handles the conference, and the system indicates the active channel with a red light ring on the microphone. External control and system integration such as Crestron and AMX is available through a rear-panel RS-232 connection. The chairman console C1-Ci has a priority button and an LCD screen with menu navigation.
Among the many large-scale conferencing options from Taiden is the HCS-4100 digital conference system, a heavyweight contender for large, multilingual gatherings where a bank of interpreters may be present.
The HCS-4100 can make up to 64 channels available over a single daisy-chained cable through Taiden's MCA-Stream digital audio processing. The main unit features LCD menus for configuration, RCA audio outputs, a record in/out port, a balanced line-in connection, alarm signal interface, a balanced output for mixed audio send, and six independent mic outputs for multi-track recording on the HCS-4120M series professional video and audio recorder module.
System capacity can be expanded with the HCS-4100ME to a maximum of 378 interpretation units and 4,096 discussion/voting units. With PC configuration, video tracking and switching can be added. Numerous contributor desk stations may be used. Among these is the HCS-4386C chairman unit, which features an electret condenser mic with an illuminated ring for active mic indication. The unit includes an integrated speaker, two headphone jacks with level control, mic on/off, five voting buttons, and a two-digit channel display with up/down selection buttons that are activated when headphones are connected.
The TS-800 series infrared wireless conference system from TOA Electronics can include up to 64 chairman/delegate stations (96 with the TS-900), as well as accept audio input from an external source. Other features include a control over the maximum number of microphones that can be on at any time, auto mic-off, speaker restriction to prevent interruptions, and installation status checkup to verify the configuration settings at any time. Of course, the system offers the typical advantages of an infrared product with high security and cable-free deployment of the mic stations.
The TS-900 system adds three-choice voting and instant tabulation and a second audio channel for bilingual conferencing. The microphones on the mic stations are available in two lengths — 14.5in. and 20.5in. The chairman unit can override any delegate unit with a priority function, and the base unit can even be mounted on a microphone stand. Mic stations are equipped with integral speakers, and the base unit includes an audio output for recording. Battery time on chairman and delegate units is about 10 hours, but AC operation is also available.
Among the medium- to large-venue conferencing systems, digital technology has presented more configuration options, automated mixing, and system expandability, while infrared systems can now offer some unique security features with relatively low cost and simple setup. Although these modern features have made the product selection process more complex, a more perfectly suited system can be found for any venue. Once you have made basic decisions, such as whether to go with a portable versus permanent, cabled or wireless system, and chosen features such as security level, style, and channel capability, selecting the final system should be fairly straightforward.
For More Information
Danish Interpretation Systems
IRP Professional Sound Products
Media Vision USA
Bennett Liles is a freelance television production engineer and AV technician in the Atlanta area. He specializes in government video production, distance learning, and videoconferencing.
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