Operation Modes - Apex Digital Argos User Manual

Operation modes.

GENERAL
The operation of the ARGOS can be based on three different sources :
• Microphone
• Line
• Loudspeaker signal
THE 3 OPERATION MODES
Microphone:
The best way is to base the operation on the actually measured sound level by means of a
microphone placed in the room. The ARGOS measures the sound pressure level in exactly
the same way as a sound level (dB) meter used by the authorities. Those parts of the audio
chain that are connected at the output of the ARGOS have no effect on the maximum feasi-
ble sound level. The position of the volume controls on the amplifier(s), the number of ampli-
fiers and speakers or the efficiency of the loudspeakers don't have any effect. If the ARGOS
is used in microphone-mode, the SLOW response is automatically selected to make sure that
sudden crossings of the threshold caused by external noise sources (voices, sounds with an
impulsive character) have no effect on the operation.
Line:
The ARGOS bases its operation on its own output signal (line-outputs). The amplifier(s) and
speakers are not part of the servo loop so the gain reduction is not based on a measurement
of the sound pressure generated by the speakers as in the microphone operation mode.
This Line operation mode is particularly suited in those cases where the maximum allowed
SPL is low (<80dBA).
If the ARGOS is used to protect an installation from damage or if it is used as a sound
leveler, this is also the best solution.
If used as a sound level limiter, calibration should take place at maximum volume settings on
the amplifier(s), to make sure that after installation no higher sound pressure levels can be
reached.
Loudspeaker:
In these cases where only one amplifier is used and the maximum admissible SPL is low, the
operation can be based on the speaker output signal of the amplifier. As such the amplifier
becomes part of the servo loop. Therefore the volume settings on the amplifier have no effect
on the maximum attainable SPL.
FAST/SLOW settings:
In the position Line or Speaker the user can choose between fast or slow operation.
In these cases where a maximum SPL should not even be exceeded for a short period, one
should choose the "FAST" position. However, this setting has the following drawback: if the
input signal is too high and the ARGOS has to decrease the level constantly, the operation
can become audible. In this situation it is important to adjust the input signal on the mixing
desk or preamplifier in such a way that the ARGOS can operate with a minimum of gain
reduction.
However, if it is important to keep the average sound level below a certain limit, the best
choice is the "SLOW" response.
This is also the best position if the ARGOS is used as a sound leveler or to protect loud-
speakers and amplifiers of getting damaged because of excessive sound levels.
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