Symetrix 371 SPL computer
371
SPL Computer
A P P L I C AT I O N S
Restaurants
Retail Stores
Casinos
Offices
The Symetrix 371 SPL
Computer automatically raises
and lowers sound system
levels in response to changes
in ambient noise conditions.
Designed for installations
featuring foreground music
and/or paging, it ensures that
music and announcements
are always clearly audible and
distinct, but never too loud.
Proprietary AmbiSense™
technology enables the 371
to continuously monitor
changing ambient noise
levels—not just during gaps
in the audio program—so it
can respond quickly to
sudden changes.
A simple set of step-through
menus displayed on the front
panel LCD guides you
through setup of the 371. You
set the parameters of the
acoustic environment and
then set the way you want the
unit to respond to changes in
it. In operation, the 371 tracks
environmental noise levels,
internal signal levels and all
the control settings. It makes
appropriate gain changes
whenever it finds measured
noise levels that deviate from
the stored performance
characteristics. Menu adjustments determine how much
the gain is changed, and how
quickly that change occurs.
Transit Stations
Hospitals
Simple calibration, precise
performance, and value
priced. Backed by our 15-year
history of SPL processing
innovation, the Symetrix 371
offers a complete and
affordable solution for audio
level management.
F E AT U R E S
Uses Microphone for
Noise Sensing
The 371 uses an external microphone to measure
changes in the ambient noise level.
Continuously Monitors Proprietary AmbiSense™ technology responds to
Ambient Noise Levels
environmental noise changes in real time—not just
during gaps in audio program.
Headphone Monitoring Monitor the sense signal using a separate front
panel headphone output.
Sense Signal
3 Operating Modes
Display numeric reading and relative bargraph of
the signal appearing at the sense terminals.
Easy Calibration
Perform calibration under typical installation
conditions. No waiting for the quietest or noisiest
ambient environment.
Phantom Power
Sense input provides microphone with 15V
phantom power. Enable or disable through front
panel menu adjustment.
Ratio Adjustment
Choose an adjustment ratio of SPL change vs.
program level change.
Gain Controls
Set minimum and maximum limits for SPL gain
range between +20 to –30 dB.
Active—Indicates continuous measurement of the
ambient noise level.
Adjust gain of sense input and line output through
menu selection. Connect an external trim pot to
the 371's rear panel to control output gain
remotely.
History—Displays the lowest and highest SPL
readings from when the unit was last reset.
Bypass—Bypasses the gain control of the SPL
controller and the AGC.
Signal Path
Controls mono or stereo signals through Euroblock
connectors.
Averaging Time
Choose integration time of the running average SPL.
Ducker Control
Ducker input provides momentary reduction of
program level (from 0 db to –40 dB) and inhibits
sense operation for the duration of externally
supplied control signal.
R E A R PA N E L
SIGNAL FLOW DIAGRAM
LINE
INPUT
LEFT
A R C H I T E C T S A N D E N G I N E E R S S P E C I F I C AT I O N S
BAL
INPUT
VCA
LINE OUTPUT
LEFT
VCA
LINE OUTPUT
RIGHT
RMS
DETECT
LINE
INPUT
RIGHT
BAL
INPUT
DUCK /
PAGE
TRIGGER
INPUT
BAL
INPUT
AVERAGE
LEVEL
DETECT
ADJUST
SPL
CPU
CALIBRATE
REMOTE
GAIN
TRIM
DC
AMP
MENU EXIT
MENU NEXT
PHANTOM
POWER
SENSE
INPUT
MIC
/LINE
INPUT
SENSE
GAIN
RMS
DETECT
SENSE
MONITOR
VOLUME
BANDASS
FILTER
SENSE
HEADPHONE
AC C E S S O R I E S
19" Rackmount Tray height is 1U
#RM-3
Filler Panel covers unused half of rack tray
#FP-3
Y Power Cable connects a 371 with any other 300 Series product
#PY-3
RC-3 Remote Control controls one volume channel
#RC-3
S P E C I F I C AT I O N S
Input/Output
Maximum Input Level
Program Input Impedance
The Ambient Level Controller (ALC)
shall control the output level of the
sound system in response to the
observed acoustical noise level
within the controlled space during
system operation. The ALC shall
utilize an external microphone to
sense the ambient noise level.
These measurements shall be made
continuously. The ALC shall
accommodate musical or paging
program signals. Provision shall be
made for the user to monitor the
audio signal used by the ambient
sense system by using headphones.
The ALC shall provide useradjustable parameters to alter the
way that it responds to changes in
the ambient noise level. These
parameters are: minimum and
maximum gain through the device,
gain:sense ratio, and averaging
time. In addition, the ALC shall
provide active mode, bypass mode,
and a history mode that collects
and displays ambient noise history
from the controlled space. The
sense input shall accept either mic
or line level signal. The sense input
gain shall be adjustable, and 15 volt
phantom power shall be available.
A master output level control shall
also be provided.
The ALC shall provide two
independent line level balanced
inputs and outputs that control two
audio signals. The maximum input
level shall be +20 dBu and the
maximum output level shall be
+26 dBu (+22 dBm into 600 ohms)
balanced. The balanced input
impedance shall be 20,000 ohms
and the output source impedance
shall be 200 ohms balanced, 100
ohms unbalanced. The gain control
range shall be –30 dB to +20 dB.
The frequency response shall be
20 Hz to 20 kHz +0/–1 dB with
THD+N less than 0.025% at +4 dBu
over the same range of frequencies.
The output noise of the device shall
be less than –95 dBu (20 kHz noise
bandwidth, unity gain). The input
and output configuration shall be
active balanced.
All connections shall utilize barrierstyle terminal strips. In addition to
the audio input/output connections, there shall be a connection
provided for a ducker input. The
ducker circuit will have an
adjustable threshold and will
inhibit response to changes in
ambient level when signals applied
to the ducker input are above the
threshold level.
A front panel power indicator shall
be provided. A liquid crystal display
shall be provided to communicate
operating parameters and setup
information with the user. A
lockout function shall be available
to prevent parameter setting
changes by unauthorized users.
The ALC shall occupy half of the
width of one rack space and shall
be housed in a metal enclosure. It
shall use an external, safety agency
approved, power supply. The
Ambient Level Controller shall be
the Symetrix model 371 SPL
Computer.
+20 dBu balanced, +20 dBu unbalanced
>20 k ohms balanced, >10 k ohms unbalanced
Input Common Mode Rejection
>40 dB
Maximum Output Level
Output Impedance
Connections
+26 dBu balanced (20 k ohm load)
Line Inputs, Sense Input, Ducker Control,
+22 dBm balanced (600 ohm load)
Remote Gain, Line Outputs
200 ohms balanced, 100 ohms unbalanced
Power In
Euroblock
7-pin DIN
Headphone
1/4 in. TRS, will drive mono or stereo headphones
Performance Data
Program Frequency Response
Program Path THD+N
Output Gain Limits
Sense Channel Frequency Response
Sense Channel Gain
Additional Headphone Monitor Gain
Program Channel Output Noise
Master Output Level Adjustment Range
20 Hz to 20 kHz, +0, –1 dB
<0.025% (+4 dBu in, +4 dBu out)
Physical
Size (H x W x D)
–3 dB at 300 Hz and 6000 Hz
1/2 rack unit
1.75 in. x 8.5 in. x 6.5 in. / 4.445 cm x 21.59 cm x 15.875 cm
+20, –30 dB
Shipping Weight
4.5 lbs./ 2.03 kg
selectable, 0 dB to +70 dB
28 dB maximum
–95 dBu @ unity gain, typical
+/–10 dB internal,
+10 dB to –50 dB remote
Symetrix, Inc.
6408 216th St. SW
Mountlake Terrace WA 98043 USA
Electrical
Power Requirements
PS-3
PS-3E
Tel 425.778.7728
Fax 425.778.7727
www.symetrixaudio.com
10 W maximum, Symetrix PS-3 or PS-3E only
115 V, 60 Hz AC nominal
230 V, 50 Hz to 60 Hz AC nominal
© 2001 Symetrix, Inc. All rights reserved. All
specifications are subject to change without
notice. Symetrix products are manufactured
in the USA.
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