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Tech Showcase: Boundary Microphones and Automixers

Plug it in, lay it on the table and it works. Boundary mics have long been the perfect solution for conference rooms where no one wants to wear their own microphone but speech pickup must be intelligible. At the other end of the line is the automixer although this device has evolved to operate in much more complex setups. Both have simplified the task of recording high quality sound and they have reduced the load on operators. The models covered here demonstrate their popularity and strong market segment.

The PZM-10 boundary mic from AKG has a very low profile design for wall or table mounting and it provides a hemispherical pickup pattern. Buyers have a choice between the PZM-10 with mic level output or the PZM10LL with a line level signal. Each mounts in a 25/32-in. diameter hole. The PZM-10 requires 12-48V phantom power. Frequencies below the voice range are rolled off to attenuate LF room noise. AKG also offers the DMM14 U digital automatic microphone mixer with 12 analog, 2 USB and 4 Dante input channels. Each unit also has 6 analog output channels, 2 USB and 22 Dante outputs. There are six programmable presets and up to ten of the mixers can be cascaded for up to 140 auto-mixed channels.

Audio-Technica is now shipping its updated UniPoint U891 Boundary Microphone models featuring a two-state RGB LED status indicator and a touch-sensitive capacitive-type user switch that can be set to three modes, replacing the previously available models. All new U891 models are equipped with an 80 Hz low-cut UniSteep filter to reduce pickup of low-frequency ambient noise, providing immunity from radio frequency interference and a unique PivotPoint rotating connector that changes the cable exit point without the need for tools. All feature a heavy die-cast case and silicon foam bottom pads to minimize coupling of surface vibration to the microphone. Threaded inserts on the bottom of the microphone allow it to be mounted with screws for increased security. The unit’s self-contained electronics eliminate the need for an external power module. All models accept available interchangeable elements that permit angle of acceptance from 100-degree to 360-degree. Models include the remote-capable U891RCb wide range condenser with a cardioid polar pattern; U891Rb) omnidirectional cardioid condenser; and the U891Rb update to the U891RCx.

Audix designed the M60 boundary condenser microphone for immunity to RF interference in boardrooms and conference environments with its heavy duty brass housing, integrated electronics and “hemi-cardioid” pickup pattern. The bottom of the case is fitted with shock absorbent material for dampening vibration. Two threaded holes are provided to allow the mic to be permanently attached to any flat surface. The 1ft. shielded cable can exit the housing at either 180 degrees for temporary surface mounting or 90 degrees for passing the cable through a drilled hole. The cable can be fitted with either an XLR or Phoenix connector and the mic operates on 18 – 52 V phantom power.

The beyerdynamic Classis BM 52 has a half-cardioid pickup pattern and a choice of operating modes including ON/OFF, PushTo-Talk (PTT) and Push-To-Mute (PTM). The two-stage bass roll-off can be used to customize the response to the room. The silent membrane operating key has a braille inscription and an LED indicates the ready-to-speak status. The case is covered with a dust repellant fabric and the non-glare finish gives the mic an unobtrusive appearance. Studio technology rejects RF interference while the linear frequency response picks up speech very clearly. The remote controllable mic can be activated with an external button and a separate device such as a video camera can be controlled with a MOSFET output.

For the simplest way to record meeting notes, conferences or adding a voice track to slide presentations, CAD Audio has the solution with their U7 USB boundary omnidirectional condenser microphone. The 10ft. cable can be connected directly to a computer for quick recording on laptops or desktop machines. The frequency response is configured to provide the clear, high quality speech response and intelligibility and the mic is run on 5V USB bus power. No extra outboard power supply is needed. The black triangular housing blends into the room environment and there is an LED power indicator on the top.

The ClearOne Unidirectional Table Top Microphone is made for conferencing and its very low profile and black case blend into the conference room environment. At the end of its cable is a standard male XLR for direct connection to any professional mic mixer or system. The unidirectional pattern and built-in low-cut filter work to minimize background noise. The unit runs on 9-52VDC phantom power and it can handle up to 141dB maximum SPL. On the mixing and transmission end of things the ClearOne Converge Pro 2 120 advanced multi-channel microphone automixer includes advanced DSP with 12 configurable mic/line inputs. It adds USB audio and USB control while the front panel LEDs provide operational information and error notification.

The MR88 Digital 8 channel Automatic Microphone Mixer from Clockaudio can be used in a free standing or rack mounted configuration and it can be set up on the front panel or by remote from a PC via RS232. Each of the eight input channels uses a balanced XLR connection and the main outputs are XLR. Each channel also has its own record output on RCA connectors. The front panel also has an LED output level indicator and adjustable limiters on each input prevent channel overloads. A headphone output has its own volume control. 48V phantom power is individually selectable for each channel and NOMA operation can be turned on or off. There is also security mode operation and external TTL control and monitoring of channel selection.

The DPA Microphones d:sign 4060 omni boundary layer mic can virtually disappear into a white table top with its stainless steel finish. It is equipped with a rubber disk on the bottom to hold it in place and prevent sliding across the table. The unit is delivered with a detachable 10ft. cable terminated with a DPA MicroDot connector and a DAD6001 XLR Adapter is also provided. The frequency range is 20 Hz – 14 kHz, with a 7 dB soft boost at 8 kHz.

The Model E-2A Automatic Mixing Controller from Dan Dugan Sound Design is equipped for 28 channels of processing, 12 Analog plus 16 ADAT using Dugan algorithms Speech System, Music System and Gain Limiting. It features a six-bus pre/post matrix mixer, four switched Ethernet ports available for a control network and physical remote control from the Dugan Model K Control Surface sold separately. On the front panel is a small display that can be used for setup and operation. Up to 8 units can be linked into one system in an optical ring network. The mixer accepts 12 VDC on a coaxial connector or it can operate with an external 100-240 VAC adaptor. Two of the single rack height devices can be mounted side by side using provided hardware.

For permanent conference table mounted applications the Earthworks IMDL1 directional boundary microphone can provide the appropriate pickup pattern and its speech optimization work to minimize room noise and it is shielded against RF interference. The mic is compatible with all DSP systems that provide 24-48V phantom power. The dual-color LumiComm light ring and touch sensor output found in the IMDL1 models lets installers program the microphone’s function and LED color. The top measures only 1.6in. across and it is available in black or stainless steel finish. The low profile unit has 30kHz extended frequency response and provides high gain before feedback. The LumiComm dual color LED touch ring requires an external power source of 8 – 28VDC @ 85-170mA.

To provide analog and digital inputs into a Dante network, Lectrosonics has the DNT16i processor with 16 Dante digital inputs and 16 mic/line analog inputs with 48V phantom power. There are 48 independent automatic mixers with 36 inputs per mixer and channel activity detectors. The unit supports both switched and redundant modes in Dante operation. With multi-level mixing, mixes can be looped back and used as mixer inputs. Extensive signal processing provides filters, delay and channel linking for compression and limiters. There are also four test signal generators for setup and calibration of sound systems. The DNT16i can be controlled via USB, RS232, Ethernet and programmable logic I/O. The built-in Ethernet switch allows operation with either port in the Switched mode with a single network, and as primary and secondary ports in the Redundant mode with two networks.

The AC-404 USB powered boundary microphone from MXL is used for easy conferencing setups and it includes a 1/8in. headphone output next to the USB connection that can also be used as a recording output. The mic has a 180-degree pickup pattern with a range of about 25ft. Available in either white or black finish, the AC-404 has plug and play connectivity with Mac and PC computers. It is compatible with both USB 1.1 and USB 2.0 The case is all metal construction and its low profile keeps it out of the way while in use. The 40Hz-16kHz frequency response allows the mic to reproduce very clear speech for conferences.

The RCF USA MC 5002 professional desktop microphone has a sturdy white finish metal case and it is supplied with a 3m cable that attaches to its mini XLR connector. The mic has a frequency response (+/- 3dB) of 50Hz to 18kHz and it runs on 12-48VDC phantom power. There are selectable flat, boost and low cut modes for low end response and when the mic is turned on, a red LED lights on its top. The audio port includes a pair of dry contacts for control.

Sennheiser can provide their MEB 114 table top boundary microphone in either black or white finish to match the room décor and its semi-cardioid polar pattern handles clear speech pickup for conferences. Its miniature XLR-3 connector is rugged enough for the conference room but small enough to virtually disappear. Running on 12-24V phantom power, the mic exhibits a 40 Hz – 20 kHz frequency response and it can handle up to a 140dB sound pressure level with an A-weighted dynamic range of 111dB. The MEB 114S includes a programmable surface button that can operate in push-to-talk, push-to-mute, toggle on/off or permanent on modes. There is also a bicolor LED ring for status indication. A camera or media control system can be triggered via the TTL logic output on the bottom side.

The Shure MX395 low profile boundary microphones provide maximum speech coverage with minimum visible profile with a selection of colors and polar patterns including omnidirectional, caridoid and bidirectional. Available in black, white or aluminum finish, the mic uses CommShield Technology to reject RF interference and the LED models feature a bi-color status indicator and a logic input for remote LED control. On the unit’s body there is a DIP switch that can be used to adjust low frequency response. The case can be installed through a 1in. hole in the conference table and secured with a large wingnut from the bottom. The LED models have a 5-pin XLR connector to wire the microphone to an automatic mixer or other logic device. Shure also offers the SCM820 digital Intellimix automatic mixer with Dante audio, up to 96 input channels and third party control system compatibility. Dynamic channel gating and attenuation reduce background noise and Open Microphones Attenuation determines the amount of gain attenuation for a mix output when the number of active microphones changes. MaxBus allows only one channel to be opened per sound source.

When automixing has to go on the road, Sound Devices has the 688 12-input field production automatic mixer and 16-track recorder. This model records timecode-stamped WAV and mp3 files to SD and CompactFlash cards. It has eight output busses, PowerSafe to protect those files from power loss, adjustable input and output delay, three camera returns and dedicated COM return along with a USB keyboard for metadata entry. The mixer can be powered five AA batteries or external 10-18VDC. With batteries, the unit weighs about 5lbs. The integral front panel meter shows input channel and output levels.

The TOA Electronics EM-700 boundary condenser microphone is intended to be stylish, compact and to provide clear speech pickup with extended high frequency response of 35Hz to 20kHz. The cardioid polar pattern and switched low cut filter minimize background noise. The EM-700 operates on 9 to 52VDC phantom power and the black mat die cast aluminum body is rugged for dependable use. The mic has a 24.5ft. cable and XLR connector included.

Among the range of conferencing microphones from Yamaha Unified Communications is the Elite line of wired mics including omnidirectional and cardioid versions available in black, white and brushed nickel finishes. These are protected against RF interference and for permanent installation, the optional mounting adapter can be mounted directly to a table surface. The cable can connect to the side of the housing or it can be routed through a drilled hole to conceal it. The 5-wire versions offer both local and remote control along with LED indicator lights. The units can be operated in push-to-talk, push-to-mute and mute/unmute toggle modes.

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