User guide DMX-66
page 10
Each output has a 31 band graphic equalizer. All parameters can be copied to the other EQs or individually
adjusted for each output.
Overview adaptive automixer
Automixer processing is useful in situations where multiple microphones are used, such as in churches, board
rooms, conference rooms or courtrooms. Automixer solves the typical problems that occur when multiple mics
are used.
In fact, the voice signal picked up by multiple microphones suffers from multi-path interference, also called comb
filtering. This multi-path interference affects the quality of the sound source by emphasizing sound at some
frequencies and canceling the sound at others
Moreover, multiple opened microphones could easily create multiple potential feedback loops and consequently
input gain must be limited.
Automixer is a real-time sound algorithm that automatically reduces the level of a microphone's audio signal
when it is not being used and maintain a steady limit on the overall signal level of the opened microphones.
Automixer has the following benefits:
Lowering hiss, rumble, reverberation and other extraneous noise that occur when several microphones operate
simultaneously.
Improving gain before feedback.
Reducing the comb-filtering effect.
Automixer is ideally suited for applications such as churches, board rooms, conference rooms or courtrooms.
Gating
The automixer unit controls the microphone’s state as following:
If the RMS level is above t
he current adaptive threshold, the microphone’s state is open i.e. the block applies no
attenuation to the signal.
If the RMS level is below the current adaptive threshold, the microphone’s state is attenuated i.e. the block
applies an off attenuation to the signal.
Adaptive Threshold
The internal algorithm dynamically sets the gate threshold level in accordance with the ambient noise. For
example, in a noisy room the automixer would increase the threshold level to prevent any of the microphone
channels from being triggered on by the noise. On the other hand, in a quiet environment, the threshold level
must be lowered.
Off Attenuation
Automixer algorithm attenuates the signal using a ramped gain control. The resulting behavior is a smooth
transition from one state to the other.
Thus, reliable, quick acting, noise-free gating and pleasant sounding turn on and turn off characteristics are
achieved.
NOM Gain
The NOM (Number of Open Microphones) attenuation control circuitry automatically adjusts gain level according
to the number of active inputs. This allows the system to deliver maximum acoustic gain while preventing
feedback.
Last Microphone Hold
Last Microphone Hold feature keeps the most recently activated microphone even if the sound level drops
below the threshold setting.