572
2
Do You Have The Right Unit?
Symetrix makes two different SPL computers: the 571 and the 572. Although both units perform
essentially the same task, they are different.
The 571 requires an external sensing microphone(s) to monitor ambient conditions. The 571 works
in real time; adjustments are made continuously, regardless of music, paging, or silence. The 571
does not interrupt the signal path at any time.
The 572 uses the sound system loudspeaker(s) to monitor ambient conditions. Doing this requires
the 572 to monitor the incoming program material for silent sections. Once the 572 detects silence,
it switches to sense mode, switching the loudspeaker(s) from the amplifier output to its sense
input. Sensing takes one to two seconds. Any signal applied to the paging inputs during this time
immediately terminates the sense period. If a silent period never occurs, the 572 forces one. A
front-panel control determines the length of time that elapses before a forced sense occurs.
Sensing may also be triggered externally. The 572 interrupts the signal path during sensing. Table
1-1 provides a tabular comparison of the two units.
Feature
571
572
Uses dedicated microphone for ambient sensing ............................. Y
N
Uses sound system speakers for ambient sensing ............................ N
Y
Sound system loudness controlled by ambient noise conditions ..... Y
Y
Continuous, real time operation ....................................................... Y
N
Program silence sensing triggers ambient sense period .................. N
Y
Mic and line level paging inputs ...................................................... Y
Y
Page over music (ducking) ............................................................... Y
Y
Music + page mixing ........................................................................ Y
Y
Calibration required ......................................................................... Y
Y
Timed ambient sensing .................................................................... N
Y
Interrupts signal path during sensing ............................................... N
Y
Table 1-1. 571 - 572 Feature comparison.
