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Tech Roundup: Boundary Mics and Automixers 2021

Long a favorite in conferences and classrooms, the boundary microphone has made its mark by providing unobtrusive sound quality while the automatic microphone mixer has enabled unscripted panel shows in particular to shed reverberation and avoid microphone up-cuts. One of these devices represents an ingenious use of basic boundary layer audio physics and the other employs increasingly sophisticated algorithms to strategically assist even the most experienced sound operator. Both devices represent major advances in audio technology that challenge modern users to imagine a professional realm without them.

The AKG CBL201 is a dual element cardioid pattern boundary layer mic that features easy talk/mute control by touching the mic and a color coded LED ring that indicates the current operation mode depending on the setting of two hidden toggle switches. The mic also offers RF interference protection and a connection for external mute control. The AKG DMM8 UL automatic mixer has 12-band graphic EQ on its outputs, six programmable presets, and t wo-cha n nel streaming in and out to interface with a local area network. As many as ten units may be cascaded to provide control for up to 80 channels. Various output mixes can be created through the audio matrix capability to route all inputs to all outputs.

Nearly invisible audio pickup and control is the idea behind the Audio-Technica ES947C/FM5 cardioid condenser boundary microphone. It conceals a 5-pin XLR output connector that enables a remote on/mute function as well as triggering of other external devices. Its visible part above the table displays a two-state RGB LED ring with seven selectable colors that indicate the mic’s status. The cardioid pickup pattern covers 120 degrees and the unit is shielded from radio frequency interference. The tough metal case houses its own power module and on top is a two-layer steel mesh protective grille. Rubber isolators prevent vibration contact between the metal case and the table top. The Audio-Technica ATDM-0604 automatic mic mixer with its SmartMixer Technology can fit into very tight spaces while allowing channels to be mixed automatically in gate or gain sharing mode. On the front panel display or from a Windows computer, users can make gain adjustments, operate phantom power, set and recall presets, and change IP configuration.

The Audix ADX60 boundary condenser microphone can handle a wide range of applications including conferencing, stage and broadcast uses. Its hemicardioid pickup pattern favors the specific area toward which the mic is oriented. Operating on 9-52V phantom power, the mic comes with a power adapter (APS910) and 25ft. cable. The mini-XLR cable connection is nearly invisible and the die cast zinc body with steel mesh screen on top provide ample protection with a stylish look. Full-bodied voice pickup is made possible through the microphone’s 50Hz-18kHz frequency response. The mic is also equipped with a rubber base to dampen vibration from a table surface.

The durability of the elastic bearing ring isolated beyerdynamic Classis BM 34 boundary layer microphone is matched by its vocal friendly 150Hz-18kHz frequency response and 60dB signal to noise ratio. At home in a table top or a ceiling mount arrangement, the mic exhibits very sensitive pickup of voices from a distance with its half cardioid pattern allowing users to move freely around the room with no acoustic dead areas. The Classis BM 34 is also equipped with a bass roll-off filter to attenuate excessive room boom. This model is available in a black, white or silver finish to perfectly match any room, ceiling or conference table. All of the Classis BM series microphones feature the Scudio technology, making them insensitive to wireless communication devices such as mobile phones.

The CAD Audio Astatic 210 button microphone is designed specifically to pick up vocal frequencies in a 360-degree pattern and output at an adjustable line level. This performance is enhanced by an integrated 150Hz, 6dB per octave high-pass filter and a signal level limiter. The microphone is shielded from RF interference and architectural surface vibration is dampened by shock absorbing polymer bushings. These features make it suitable for application not only in conference rooms but also for security and observation. The integrated volume control is located on the side of the microphone and is protected from tampering when the mic is installed. A 3.5mm terminal block connection on the bottom of the mic accepts DC power and it sends out an unbalanced, amplified signal.

For multiple use huddle rooms, the Clearone CONVERGE Huddle is a powerful DSP unit featuring three balanced audio mic/line inputs with Distributed Echo Cancellation on every mic input. It also has two balanced line outputs and dual 10W speaker outputs. Small enough to mount under a table, on a wall, behind a display, or in a half-rack space, the unit is perfectly compatible with third party mics, cameras and speakers. The camera connection is a USB 3.0 Type A port on the front panel where there are also location, status and power LED indicators. On the rear panel, in addition to the other input and output ports, there is also a headphone connection and an RJ-45 pass-through with PoE.

Not only superior in its performance specs, the Clockaudio ARM 202-RF cardioid boundary layer mic is impressive with its motorized operation. Two independently powered microphone capsules are built into the housing which, until it is activated by a remote switch to rise, protrudes only two millimeters above a conference table surface. Available in Black Nextel, Satin Nickel or Nextel Suede custom coating finishes, the microphone is RF shielded and solidly constructed of brass. The 50Hz-18kHz frequency response produces full voice response and the 125dB maximum sound pressure level avoids distortion on vocal peak sounds. The condenser mic operates on 9-48V phantom power. The MR 88 8-channel automatic microphone mixer is rack mountable with mic/line input levels and recording outputs on every channel. The multi-level channel priority system gives the auto-mixing a natural sound. There are also adjustable limiters for each channel.

Whether it’s on a table or any other flat surface, even with the sound source at a distance, the DPA BLM4060 displays good sensitivity and a broad 20Hz-14kHz (+/-2dB) effective frequency range with 7dB soft boost at 8kHz. The mic is supplied with a 10ft. cable terminated at both ends with a MicroDot connector. It can also take sound pressure levels up to 134 dB before clipping. The omnidirectional condenser element is attached to a black rubber disk housed in a 4in. diameter stainless steel base that blends with any room décor. Operating on 12-48V phantom power, the mic can cover the sound area from a conference table up to 20ft. long.

The Dan Dugan Sound Design E-3A Automatic Mixing Controller is a product from the famous pioneer who wrote the book on automatic microphone mixers. This unit can be connected to the input patch points of the main mixer so that each mic channel is processed independently and fed back into its own channel on the main mixer. A second option involves internal mix busses on the E-3A handling the processing and outputting a summed signal to the main mixer. It can eliminate up-cuts and reduce gain to eliminate acoustic feedback when two panelists are talking simultaneously. The E-3A can process up to 16 AES and 16 ADAT channels while being controlled remotely from the Dugan Control Panel for Java, Dugan Control Panel for iPad or the Dugan Model K Control Surface, as well as from the front panel.

For nearly invisible installation and compatibility with all DSP systems that provide 24-48V phantom power, the Earthworks IMDL1 directional boundary mic is the right call. This model picks up pure speech in tight areas with an audio response range that extends to 30kHz (+/-2dB). Operating on 24-48V phantom power, the mic can handle an SPL up to 145dB and it is available in black or stainless finish. It is also available with the LumiComm Touch Ring that consists of a dualcolor LED light ring and a touch sensor output that works with an external media control system.

The Lectrosonics DNT16i Digital Processor is a sophisticated device that can handle any automixing scenario with its 48 independent automatic mixers, 36 inputs per mixer, and channel activity detectors. Mixes can also be looped back and used as mixer inputs. Features include signal processing with filters, delay and channel linking for dynamic processing as well as gain smoothing. The chassis is small enough for rack mounting or it can easily go under a table. Remote control options include USB, RS-232, Ethernet and programmable logic I/O. There are 16 mic/ line analog inputs with 48V phantom power and wide range gain control, 16 DanteTM digital inputs, and 32 DanteTM digital outputs.

A unique 3-capsule boundary design allows the MXL AC-44 to emphasize direct voice pickup in a 180-degree cardioid pattern while minimizing sound from the back of the microphone. Connection is simplified by a USB-C terminal with no drivers necessary. Just next to that is a 1/8in. audio mini output connector for recording. The sturdy metal frame and metal grille on top protect against damage from impacts. The case is only 2.5in. by 3.5in. and the mic extends only an inch above the table surface. Included is a 6ft. USB-A to USB-C cable. The mic is available in white, black, and cobalt.

Maximum features in minimum space is the idea behind the RCF MC 5002 Professional Desktop Microphone. The tough white metal body can be carried around and used in the most physically challenging environments. The switch on top is very easy for any non-tech conference participant to use and the red LED on the body indicates when the mic is on. The unidirectional condenser unit runs on 12-48V phantom power and there is a three meter cable terminated in a mini XLR included. 50Hz-18kHz (+/-2dB) frequency response picks up speech very well and the mic can be used in FLAT, BOOST and LOW CUT modes.

The Sennheiser SL Boundary 114-S DW wireless table boundary microphone combines versatility in operational settings with complete freedom in placement. Its programmable top button can be set up for Toggle ON/Toggle OFF, push-to-mute, push-to-talk, and permanent ON. When any of those selections are made, the LED status indicator responds with visual confirmation. The internal battery can be charged on a USB connection or wirelessly by induction using the separately available wireless power transmitter CHG 2W for two mobile devices. The SL Boundary 114-S DW is also compatible with the SL Rack Receiver DW and can be monitored and controlled remotely with the Sennheiser Control Cockpit app. The cardioid polar pattern slightly favors the front of the unit and the wide 40Hz-20kHz frequency response assures perfect vocal quality.

Pickup pattern control on boundary mics can be a challenge but it is one that has been met by the Shure MX396 Microflex MultiElement Boundary Microphone. Available in two and three-element configurations, the mic has an individual audio output for each element. This allows custom tailored pickup to suit the room size, conference table design, and participant seating arrangement. There is a programmable multi-function mute switch on the top with a logic output. The internal DIP switches can be set to allow an external device such as an automatic mic mixer to mute the microphone. Each pickup element requires 12-48V phantom power and the device uses its CommShield technology for filtering RF interference. The control end of things is covered by the Shure SCM820 Digital IntelliMix Automatic Mixer. This unit has multiple I/O configurations and networking options including per-channel direct outputs, independent automixes to the mix A and B outputs, aux inputs on the front and back panel, and gain level LED meter rings on each input. Windows 10 control software handles routing, monitoring, and configuration. Standard Ethernet or Dante digital networked audio configurations available. The SCM820 is also AMX and Crestron control system compatible.

Taking it on the road is the award-winning Sound Devices Scorpio Premium Portable Mixer-Recorder with 16 mic/line preamplifiers, 32 channels of Dante in/out, AES in/out, 12 analog outputs, and multiple headphone outputs. Recordings are made on 256 GB internal SSD and two SD card slots. Operators have the ability to route any input to any channel, bus, or output and there are built-in analog limiters, high pass filters, delay, 3-band EQ, and phantom power. Up to 16 channels can be automixed at a time, and two separate groups can be mixed simultaneously.

The TOA Electronics EM-700 Boundary Condenser Microphone is designed with a pattern that favors sound from the front while rejecting general room sound from other directions. The element operates on 9-52VDC phantom power and the frequency response is a wide 35Hz-20kHz without the low-cut filter which rolls off 12dB per octave below 100Hz. The filter switch is located on the bottom of the case. The body is made of die cast aluminum with a black finish. Included with the microphone is a 25.6 ft. cable terminated in an XLR.

Among the wired microphones in their line, the Yamaha Unified Communications Omnidirectional Table Top Microphone has a frequency response of 125Hz to 18kHz and signal to noise ratio of 70dB. The mic connection allows an external device to sense button presses on the housing and trigger various events and responses. The LEDs on the case indicate the microphone status. Its 87dB dynamic range assures pickup from relatively distant sources as well as undistorted output from louder sounds. Representing the ultimate in versatility in an audio processing unit, the Yamaha MRX7-D can be custom configured for any sound environment and it can use its Dante connectivity to operate with other Dante connected devices. The graphical interface of the MTX-MRX Editor is very intuitive and there is a wide range of external control options and DSP functions. The front panel includes I/O signal level indicators, a preset selector, status LEDs, and an SD card slot while the rear side has a range of I/O connections, networking ports, and remote control interfaces.


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