QSC Audio SF-3 User Manual

PERFORMANCE ACCESSORIES

1675 MacArthur Boulevard
Costa Mesa, CA 92626
Ph: 800/854-4079 or 714/957-7100
Fax: [phone]

www.qscaudio.com

SF -3

Subwoofer Filter

Basic Description

The SF-3 subwoofer filter allows the addition of subwoofers to an
existing full-range system, offering adjustable low-pass filtering and
high-pass subsonic filtering with optional B6 boost and mono-summing.
The unit mounts to the rear panel of a two-channel DCA or CX amplifiers
to save cost and rack spack. The amplifier’s DataPort provides the
accessory’s operating power and receives the output signals,eliminating
added external wiring or power transformers.

For subwoofer material derived from full-range audio, a 4

th

-order
Linkwitz-Riley low-pass filter lets you set the upper range of the sub­woofer band to 80,150, or 250 Hz.The subsonic filter offers a range of
roll-off frequencies from 20 to 50 Hz to protect subwoofers from over
excursion, with optional equalization to extend the response of B6
speaker enclosures. A trim control provides 0 to 20 dB of attenuation
for matching levels among the various frequency bands. Filter fre­quencies are programmable via provided SIP resistor networks.

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 CX 1202V

SF-3 Features

• For 2-channel DCA series or CX series amps

• Designed for professional cinema applications or installed

sound systems

•

Mounts directly to back of amplifier;inter faces with amplifier
via DataPort

•

Adds low-pass and subsonic filtering functions without requiring
additional rack space,cabling,or AC outlets

•

Precision components for accurate performance

•

Active balanced XLR inputs

•

Selectable subsonic frequencies from 20 Hz to 50 Hz

•

Defeatable 24 dB/octave low-pass filter for deriving subwoofer
program from mono or stereo full-range audio

SF-3 Spec Sheet.11/7/00

12345678910

OFF ON

Cinema processor
subwoofer output
or full-range audio

SF-3

subwoofer filter

Ch. 1

DCA amplifier

Ch. 2

QSC Audio Inc. 1675 MacArthur Boulevard • Costa Mesa, CA 92626 • Ph: 800/854-4079 or 714/957-7100 • Fax: [phone] • www.qscaudio.com

SF-3 SPECIFICATIONS

GENERAL INFORMATION

Subsonic filter frequency
Subsonic fitler Q

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; both inputs summed
Output stage type Balanced
Dynamic range 118 dB nominal
Total harmonic distortion Less than 0.1%
Signal to noise ratio Min. 103 dB
Subsonic filter type 2nd-order, 12 dB/octave
Low-pass filter type
Low-pass roll-off slope

4th-order Linkwitz-Riley alignment; -6 dB at crossover frequency

24 dB/octave rolloff

SF

-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 k‰balanced; 11.3 kΩ unbalanced

CONTROLS (each channel)

Selectable using SIP resistor networks: 20, 25,30, 35, 40 & 50 Hz

Selectable using DIP switch: 0.707 (Butterworkth) or 2 (6 dB peak)

Low-pass filter

Bypass or engage using DIP switch
Low-pass filter frequency
Gain adjustment

Selectable using SIP resistor networks: 80, 150 & 250 Hz

Trim potentiometer 0–20 dB attenuation
CONNECTORS
Input

Two female 3-pin XLR

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

Audio* in

Channel 1

Audio* in

Channel 2

SF filtering

*Either full-range (for derived subwoofer program)

or discrete subwoofer program

Level trim

0…-20 dB

SF out
Channel 1

DataPort

SF out
Channel 2