Qsc audio LF-3 User Manual
PERFORMANCE ACCESSORIES
1675 MacArthur Boulevard
Costa Mesa, CA 92626
Ph: 800/854-4079 or 714/957-7100
Fax: 714/754-6174
www.qscaudio.com
LF -3
Low Frequency FIlter
Basic Description
The LF-3 Low-Frequency filter, when used with the XC-3 two-way
crossover, provides the low-frequency crossover to create a threeway active system. The unit mounts to the rear panel of a
two-channel DCA or CX amplifiers to save cost and rack space. The
output signal andthe operating power for the unit are conducted
through the amplifier’s DataPort, eliminating added external
wiring or power transformers.
The LF-3 features two discrete channels with 4th-order LinkwitzRiley low-pass filters with 24 dB/octave slopes. Each channel has
an all-pass filter providing delay for time alignment of lowfrequency drivers with mid- or high-frequency drivers, as well as a
trim control providing 0 to 20 dB of attenuation for matching
levels among the various frequency bands. Frequency and delay
parameters for both channels are set individually. One LF-3
mounted on an amplifier will support two other amplifiers with
XC-3 accessories installed, even in stereo.
Compatible Amplifier Models
DCA 1222, DCA 1622, DCA 2422, DCA 3022, and DCA 3422
CX 302, CX 502,CX 702, CX 902, CX 1102,CX 302V, CX 602V, and CX1202V
LF-3 Features
• Compatible with 2-channel DCA series or CX series amps
• Designed for tri-amp cinema or installed sound systems
•
Adds crossover and time alignment functions without requiring
additional rack space, cabling, or AC outlets
•
Selectable low-pass frequencies from 80 to 500 Hz
•
Selectable time-alignment delays from 0.3 to 1.8 millisecond
•
Mounts directly to back of amplifier via DataPort interface
•
Precision components for accurate performance
•
Active balanced XLR inputs
LF-3 Spec Sheet.11/7/00
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ON
OFF
full-range audio
full-range audio
L
R
XC-3
2-way crossover
LF-3
low-frequency filter
XC-3
2-way crossover
Ch. 1
MF
CX or DCA amplifier
HF
Ch. 2
Ch. 1
LF
CX or DCA amplifier
LF
Ch. 2
Ch. 1
MF
CX or DCA amplifier
HF
Ch. 2
QSC Audio Inc. 1675 MacArthur Boulevard • Costa Mesa, CA 92626 • Ph: 800/854-4079 or 714/957-7100 • Fax: 714/754-6174 • www.qscaudio.com
LF-3 SPECIFICATIONS
GENERAL INFORMATION
Low-pass frequency
Output to amplifier
Accessory’s operating power
GENERAL AUDIO
Input stage type
Male HD-15 connector to amplifier DataPort
Male HD-15 connector to amplifier DataPort
Electronically balanced differential
Output stage type
3Balanced
Dynamic range
118 dB nominal
Total harmonic distortion
Less than 0.1%
Signal to noise ratio
Min. 103 dB
Low-pass filter type
4th-order Linkwitz-Riley alignment; -6 dB at crossover frequency
Low-pass roll-off type
24 dB/octave rolloff
LF-3
Supply Voltage (no load)
+15 volts provided by amplifier, -15 volts provided by internal charge-pump converter.
Supply Current Requirements
Less than 50 mA
Operating Temperature
0–70oC
Input type, each channel
Electronically balanced differential
Input impedance
22.6 kΩ balanced; 11.3 kΩ unbalanced
CONTROLS (each channel)
Selectable using SIP resistor networks: 80, 150, 200, 250, 300, 400 & 500 Hz
Time alignment (all-pass) delay
Selectable using SIP resistor networks: 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1.0, 1.3, 1.4 & 1.8 miliseconds
Low frequency delay
Bypass or engage using DIP switch
Gain adjustment
Trim potentiometer 0–20 dB attenuation
CONNECTORS
Input
Female 3-pin XLR, one per channel
5.1
Cinema
Processor
L
C
R
LS
RS
Sub
XC-3XC-3XC-3
1
2
1
2
1
2
1
2
DCA
DCA
DCA
DCA
Left
MF
Left
HF
Center
MF
Center
HF
Right
MF
Right
HF
Left
Surround
Right
Surround
LF-3LF-3SF-3
1
2
1
2
1
2
DCA
DCA
DCA
Left
LF
Center
LF
Right
LF
Spare
Sub
Sub
Full-range
audio in
Channel 1
Full-range
audio in
Channel 2
LF filtering
LF filtering
LF delay
LF delay
Level trim
0…-20 dB
LF out
Channel 1
DataPort
LF out
Channel 2
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