The Symetrix 571 SPL Computer is an automatic level controller designed to maximise intelligibility by adjusting system gain in response to changes in ambient noise levels. It effectively manages the volume of a sound system by continuously measuring environmental noise and making real-time gain adjustments.
Its operating functions are managed by a microprocessor running proprietary Symetrix software, which streamlines calibration and allows installers to optimise performance for a wide range of environments. No external test equipment is required, as the Symetrix 571 calibrates itself and stores the necessary data during setup.
The Symetrix 571 features separate inputs for paging and music, along with dual microphone inputs for sensing ambient noise and a direct input for paging microphones. A front panel control enables the page-over-music function, offering up to 14dB of music attenuation during announcements. Additionally, a front-panel LED meter displays gain changes and assists in setup and calibration.
Beyond basic volume control, the Symetrix 571 includes an averaging time control for the sensing microphones and a ratio control to fine-tune its responsiveness to ambient noise fluctuations. Its intelligent design prevents the system from making excessive gain adjustments in response to its own output, avoiding feedback loops and maintaining consistent audio levels. During calibration, the installer defines the acoustic environment and sets the response parameters, after which the Symetrix 571 automatically makes smooth, accurate adjustments to maintain optimal levels.
From racetracks and ballrooms to subway stations, the Symetrix 571 provides reliable system level control that responds to real-world noise conditions rather than relying on pre-set timers.
Both the Symetrix 571 and Symetrix 572 SPL Computers perform similar functions but are designed for different applications. The Symetrix 571 uses one or more external microphones to sense ambient noise, making it ideal for environments requiring constant paging, where levels need to adjust quickly and smoothly without interrupting the audio signal.
In contrast, the more cost-effective Symetrix 572 utilises the speaker system itself to detect changes in ambient noise. While this eliminates the need for external microphones and associated cabling, it requires periods of silence in the audio signal to function effectively as a sensor.
Features
- Constant or averaged time sensing (1.2 secs. to 5 min.)
- No runaway gain, feedback 40 dB control range
- Ignores level changes in the audio signal passing through the SPL computer
- Allows for more than one microphone to “average” a room’s ambient signal
