I receive requests on a regular basis from integrators trying to find solutions for large conference rooms, training rooms, or other environments where control of the audio needs to be addressed with little or no human interaction other than power up, source selection, dialing, and volume control. However, the complexity of the audio needs oftentimes requires more advanced functionality working in the background. These applications may call for an automixer. In short, an automixer receives audio signals, such as multiple microphones, phone lines, computers, and other sources, combines them and routes them to endpoints such as local speakers for speech reinforcement (a.k.a. “voice lift”), remote locations via phone lines, recorders, etc. One of the main benefits of an automixer is the ability to automatically turn off unused microphones in order to minimize background noise and improve gain-before-feedback. They can also decrease the output automatically to compensate for level increases that would occur when multiple people talking activates more than one microphone simultaneously – keeping the overall output to a reasonable level. Before talking technology, I start by looking at non-technical elements such as at how the room will be used and by whom, room layout(s) and acoustic elements, including construction and ceiling heights. Not all automixers are created equally. Without going too deep into the technology, let’s look at some factors to consider in narrowing choices to those options that may work for your application.
- Number of inputs. Remember to address each type of source including:
- Mics – If you are using wired condenser mics. Make sure you have phantom power.
- Line – Count stereo sources, such as CD players, as two inputs.
- Phone – Find out if you need POTS (analog) or VOIP compatibility
- USB – This simplifies sharing computer audio from presentations with local and remote participants. It is also the easiest way to connect to software based VTC CODECS. While audio connectivity from a computer can be accomplished using the line inputs and outputs, using USB reduces the number of digital to analog and analog to digital conversion stages, thereby improving quality.
- Specialized inputs – for example, the ClearOne Beamforming Mic Array is only compatible with the E-Bus on certain ClearOne Converge Pro automixers.
- Number of discreet outputs. Count the number of unique zones. If you are using ceiling speakers for voice lift, plus stereo speakers at the front of the room for playback, these will need to be on separate outputs.
- Routing flexibility – Can you get the signal to the correct output through the correct processors? For example, can you get the DVD player to the output that feeds the front speakers, without routing them to the ceiling speakers? Some applications, such as courtrooms, require the ability to route to recording devices prior to any gating, yet still gate signals routed to outputs used for voice lift. In room divide / combine scenarios, flexible routing is essential to accommodate various room configurations.
While it is imperative to ensure sure you can connect all sources and get them to where you need, the following items may also help narrow the field to identify the best solution for your application.
- Control – Do you need front panel access to most functions – which may also give end users more control than is in their best interest. Will you need third-party control via RS232? If using third-party control, do you prefer to simplify programming by having recallable presets or macros? Do you prefer an end-user- and programmer-friendly basic remote controller that emulates a telephone dial-pad? Will software-based control simplify revisions, troubleshooting, and cloning complex setups between similar rooms?
- Processing – Beyond filters (EQ), gating, ALC, AGC, etc, options can include Stereo Acoustic Echo Cancellation (AEC) or the much more effective distributed AEC. Adaptive Noise reduction can help reduce background noise in changing environments, such as can occur with cycling HVAC systems.
- System Expandability – Are changes in the future? Can the system be expanded without forklifting the original equipment from phase one?
- Built-in or external amplification – while it is easy enough add external amplification, some automixers add multiple internal low Z and 70V amplifier channels at a favorable price point.
As previously mentioned, suitable inputs, outputs, and routing, are essential to the basic functionality of a system. The remaining elements are more of a personal choice for the system designer. Please feel free to share your thoughts on what you consider important when choosing an automixer. I look forward to your comments.