Symetrix 571

Controller Amp/Mixer zur automatischen Anpassung der Beschallungslautstärke an die Umgebungslautstärke

The Symetrix 571 is an ambient noise sensing automatic level controller or SPL computer.
The 571 uses one or two sensing microphones, located in the coverage zone of the sound system,
to continuously sample the loudness of ambient sounds.
The 571’s microprocessor, running proprietary embedded software, computes how loud the sound
system should be, based on the current ambient conditions measured by the sensing
microphone(s). The gain computation uses a combination of the current ambient environment and
“experience” gained during the unit’s on-site calibration procedure. The 571 adds or subtracts
enough gain to operate the sound system at the computed level.
Semiautomatic calibration makes the 571 very easy to set up. The calibration procedure requires no
test equipment and typically takes less than one minute. Internal nonvolatile memory stores the
calibration parameters until they are changed, and the memory will survive indefinitely in the
absence of AC power. Once calibrated, the 571 predicts how the environment should respond
under all possible operating conditions. The SPL computer’s proprietary software allows the 571 to
differentiate between environmental noise and music/paging signals.
Calibrate the SPL computer and its associated sound system when the room is at its quietest.
Pressing the mode switch tells the microprocessor to begin the calibration routine. When the SET
MIN indicator flashes, use the LEVEL SET MIN control to set the sound system’s minimum output
level. When the SET MAX indicator flashes, use the LEVEL SET MAX control to set the sound
system’s maximum operating level. The SPL computer puts those settings into memory along with
their respective SPL’s, then returns the unit to normal operating mode.
The 571 also includes a mic-level paging input, a balanced line-level paging input, a balanced input
for background or foreground music, and page-over music capability (music ducking).
A multi-segment LED bargraph indicates the internal gain of the 571 during operation and serves as
a prompting device during calibration.