Boundary Microphones and Automatic Mic Mixers Technology Showcase
Aug 29, 2011 2:39 PM, by Bennett Liles
The Audio-Technica AT-MX351 is a 1RUsolution to automatic mixing of up to four microphones featuring individually selectable 48V phantom power, limiters on each mic channel, pre or post-controller audio outputs for each channel, and a TTL output and closure control input for remote control. NOM attenuation operation is included and can be turned on or off. The unit includes a headphone output with level control, an output level meter with peak, and RMS modes in addition to balanced inputs and outputs with switchable mic/line input levels.
Handling eight microphones in a 1RU chassis, the autoTwo from Biamp uses plug-in barrier connectors and features NOM attenuation, adaptive threshold sensing, selectable last mic on, and 48V phantom power. There are main and aux outputs along with stacking capability for two units. Each channel includes trim, pad and level control, combined active/peak LED, and an unbalanced direct output. On the rear panel are DIP switches to select gating, phantom power, and direct out pre/post gate.
Multiple functions, connection variety, and programming versatility are hallmarks of the Converge SR 1212A from Clearone. The digital matrix mixer is a 12-input, 12-output device with four integral 35W power amplifiers that connect to 8Ω or 70V speakers. Featuring Dynamic Automatic Resonance Elimination (DARE), ALC, AGC, and advanced digital processing on each amplifier channel, units can be linked to handle up to 96 microphones and 16 telephone lines for conferencing, training, courtrooms, churches, zoned paging, and other applications.
The Clockaudio MR88 is a DSP-microprocessor-controlled automatic switching 8-channel mic mixer with balanced low-impedance XLR inputs and balanced stereo outputs that can be switched to mic or line level. The rear-mounted VCA connector allows access to the open-collector outputs and the internal control inputs. For connection to stereo gear there are also RCA -10dB level output connections. Multiple units may be daisy chained through RCA linking ports.
The most recognizable name in auto mixing is Dan Dugan Sound Design and Dan’s latest entry is the Model E-1 automatic mixing controller with three methods of unit control. These are the front panel, the Web control panel, and the serial connection. Internal flash memory stores all four programs associated with the device operation, and the DSP firmware embodies the Dugan Speech System Algorithm. The unit can connect to the interstage patch points of an existing mixer to convert it to the automixing functions. Multiple units may be linked to act as one larger automatic mixer.
Taking configuration and function versatility to a new level, the SPN 1624 from Lectrosonics is one of several models in the Aspen line of mixers that provide a crosspoint matrix; master/slave input expandability; control by RS-232, USB, Ethernet, and the unit’s logic I/O ports. Each input is adjustable from -10dB to +60dB and a single Cat-6 connection carries data, audio, and control signals. Multiple automatic mixing and recording modes enable each input to behave differently at each output.
The Peavey Sanctuary Series S-4 provides four XLR mic and 1/4in. line level inputs in a 1RU chassis that includes 48V phantom power, selectable microphone priority, a soft-knee compressor with variable threshold, and a PFL switch on each channel for setup and testing. Individual channels also have a signal activity and peak indicator, a low-cut filter, channel insert or direct output 1/4in. connection, and an automatic/manual operation switch on inputs 3 and 4.
The AM2 Automixer from Rane can play a dual role in that it offers an eight-input standalone automixing unit with XLR connectors and individual signal and output indicator LEDs, but in addition it can use the remote audio device (RAD) port to send the mic mix over a Rane Mongoose or CobraNet network. Optimized for speech, the AM2 has a fixed 100Hz to 7kHz bandpass filter, and the main XLR output port can be set to either line or mic level. Cascade in/out connections enable each unit to be part of a larger coordinated mixing setup.
One of the most familiar members of the small automatic mic mixer group is the SCM410 4-channel mixer from Shure with its input gain knobs flanked by screwdriver-adjustable equalizer controls. The half-rack chassis includes a balanced mic/line output and an RCA auxiliary out connector. A last mic on lock-on circuit maintains ambient sound, and the mixing logic automatically adjusts for background noise. The front panel includes bi-color-channel activation and clipping LEDs along with a peak responding LED output level meter.
Symetrix designed the Automix Matrix 780 for maximum versatility in a minimum space. The 1RU mixer includes eight mic/line and four line-only inputs along with compression, AGC (gating and gain sharing), matrix mixing, feedback elimination, filters, EQ, limiting, and delay. Front-panel controls and indicators are amply augmented by the software interface, which displays a graphical mixer with all of the unit’s functions. The eight outputs can be fed in any combination for a wide variety of mix feed scenarios.
The D-901 from TOA Electronics is a digital mixer with 12-input, eight-bus, and 8-channel output functionality that also incorporates a feedback suppressor and automatic mixing based on NOM attenuation. A ducker drops the level of other inputs when one channel is active. A built-in compressor can be used along with flexible speaker crossover points and filter slopes. The unit can store up to 16 configuration presets for instant recall by front-panel buttons, and the settings can be locked. The eight-bus matrix allows flexible input-to-output signal routing for zoning and room combining.
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