QSC SF-3 Owners manual

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Cinema Accessories

for DCA Series amplifiers

USER MANUAL

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XC-3

Two-way crossover with delay

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LF-3

Low-frequency filter with delay

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SF-3

Subwoofer filter

*TD-000079-00*

TD-000079-00 rev. B

“QSC,” “DCA,” “DataPort,” and the QSC logo are registered trademarks of QSC Audio Products, Inc.

EXPLANATION OF GRAPHICAL SYMBOLS

The lightning flash with arrowhead symbol,

within an equilateral triangle, is intended to

alert the user to the presence of uninsulated

“dangerous voltage” within the product’s en-

closure that may be of sufficient magnitude to

constitute a risk of electric shock to humans.

The exclamation point within an equilateral

triangle is intended to alert the users to the

presence of important operating and mainte-

nance (servicing) instructions in the litera-

ture accompanying the product.

CAUTION: To reduce the risk of electric shock, do

not remove the cover. No user-serviceable parts

inside. Refer servicing to qualified service per-

sonnel.

WARNING: To prevent fire or electric shock, do not

expose this equipment to rain or moisture.

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

SAFEGUARDS

Electrical energy can perform many useful functions.

This unit has been engineered and manufactured to

assure your personal safety. Improper use can result

in potential electrical shock or fire hazards. In order

to not defeat the safeguards, observe the following

instructions for its installation, use and servicing.

• Maximum operating ambient temperature is 50° C.

• When installing equipment into a rack, distribute

the units evenly. Uneven weight distribution can be

hazardous.

• Connect the unit only to a QSC DCA, CX, or PL2

Series amplifier.

• Maintain reliable e

arthing (grounding) of all rack-

mounted equipment.

WARNING!

While QSC has endeavored to develope and produce the most

dependable and robust Cinema Accessory for your use, QSC

cannot be held responsible for damages resulting from any

deviation or failure by the user to strictly follow the recommen-

dations set forth in the user manual.

All risks attendant to integration of user-configurable Cinema

Accessories with your sound system are assumed by you.

While QSC strives to supply the highest quality technical

solutions, in no event will QSC or its suppliers be held liable for

any damages, consequential, incidental, or otherwise, includ-

ing any claims for lost profits and/or savings resulting from any

attempted integration of the cinema accessories which does

not strictly adhere to the manual’s recommendations.

IMPORTANT SAFETY INFORMATION: PLEASE REVIEW!

TABLE OF CONTENTS

INTRODUCTION

Introduction and description of each model.................................4

CONFIGURING THE ACCESSORIES

General configuration information, all models...............................5

XC-3

Setting up the XC-3....................................................................6

Factory-installed SIPs..........................................................6

Factory-switch settings.........................................................7

Recommended amplifier settings......................................7

LF-3

Setting up the LF-3....................................................................8

Factory-installed SIPs..........................................................9

Factory switch settings.........................................................9

Recommended amplifier settings......................................9

SF-3

Setting up the SF-3....................................................................10

Factory-installed SIPs.........................................................11

Factory switch settings.........................................................11

Recommended amplifier settings......................................11

MOUNTING TO AMPLIFIER...............................................12

APPLICATION EXAMPLE......................................................................13

WARRANTY INFORMATION.........................................14

HOW TO CONTACT QSC AUDIO PRODUCTS ....................15

Illustrations: Setup flow chart, XC-3 front and rear, delay and crossover SIP

selection charts, SIP identifier chart, and HF boost response curve.

Illustrations: Setup flow chart, LF-3 front and rear, delay and crossover SIP

selection charts, SIP identifier chart.

Illustrations: Setup flow chart, SF-3 front and rear, low-pass/high-pass SIP

selection chart, SIP identifier chart.

INTRODUCTION & DESCRIPTION OF EACH MODEL

XC-3 This accessory is a two-way crossover, with the low frequency band fed to channel 1 of the amplifier and the high frequencies to

channel 2. An all-pass filter on the low frequency band delays the audio signal, permitting time alignment of a cone driver with

a high-frequency horn. A selectable high-frequency boost circuit provides several increments of compensation for screen loss or

constant-directivity horn equalization. A HF trim control provides 0 to 20 dB of attenuation for matching levels between

frequency bands.

The XC-3 can be used by itself with one amplifier for a 2-way system (shown opposite page, bottom-left), or with the LF-3

and an additional amplifier for 3-way systems, as shown, opposite page, bottom-right. The XC-3 has a pass-through output in

parallel with the input for distributing th e audio signal to the LF-3. The filter circuitry uses a 4th-order Linkwitz-Riley alignment

with 24 dB/octave slopes.

LF-3 Used in a system with the XC-3, the LF-3 performs the low-frequency crossover functions in a 3-way system as shown, opposite

page, bottom-right. Unlike the XC-3, it has two discrete channels; one LF-3 with an amplifier will support two other amplifiers

with two XC-3 accessories, as shown. The 4th-order Linkwitz-Riley low-pass filters have 24 dB/octave slopes.

Each channel has an all-pass filter providing delay for time alignment. Frequency and delay parameters for both channels

are set individually, although typically they would be set the same.

Each channel has a trim control that provides 0 to 20 dB of attenuation for matching levels among the various frequency

bands.

SF-3 The SF-3 Subwoofer Filter has two summed inputs and a bandpass filter that defines the frequency range of the subwoofer

program. The frequencies of the 2nd-order high-pass and 4th-order Linkwitz-Riley low-pass filters are both set by the user

by selecting and installing the appropriate SIP networks. The high-pass filter also has a switchable low-frequency boost

feature: switched on, it provides a 6 dB bump at the selected high-pass frequency, useful for extending the low-end response

of some speaker systems; off, the response is a flat Butterworth curve that is 3 dB down at the selected frequency. The output

is parallel, feeding the same signal into both channels of the amplifier. The SF-3 has no delay function. A level trim control

provides 0 to 20 dB of attenuation.

The SF-3 can be used to derive subwoofer-range program from full-range audio, as shown, opposite page, bottom-left. It can

also be used with a discrete subwoofer channel in cinema sound systems.

Introduction

Description of each model

This manual covers setup and operation of cinema crossover accessories for QSC DCA Digital Cinema Amplifiers. There are three

models: the XC-3 crossover, the LF-3 low frequency filter, and the SF-3 subwoofer filter. Together with DCA amplifiers, they allow

you to assemble any type of cinema sound system, mono or multi-channel.

Each accessory mounts directly to the back of the amplifier by plugging into the amplifier’s DataPort and is secured with three screws.

Operating power and all connections between the accessory and amplifier are provided by the DataPort connection.

Frequency and delay parameters are user-adjustable by inserting selected 8-pin SIP resistor networks into sockets on the underside

of the accessory. A DIP switch permits selection of functions such as delay and high-frequency boost, depending upon model. Each

accessory includes an assortment of the proper SIP resistor networks and three mounting screws. Keep the unused SIPs for future use.

CONFIGURING THE ACCESSORIES

Configurable functions of the three accessory models

Configure each accessory before you mount it to the ampli-

fier. If an accessory is already mounted to an amplifier,

always turn the amplifier off before changing switch set-

tings, changing input or output connections, or detaching the

accessory.

Use the tables on the following pages to determine the

correct SIP resistor network value for the desired frequency

and delay settings. SIP identification charts are included to

help you identify the values of the resistor networks. A

flowchart for each model will help you properly configure the

accessory.

NOTE: Even if you don’t use a particular filter or delay

feature on an accessory, put an unused SIP resistor

network of any value into its socket to ensure circuit

stability when it is powered up.

The SIP resistor networks have no polarity and therefore do

not need to be inserted in a certain direction. Make sure all

eight pins are inserted properly into the socket holes, and

then gently but firmly press the network into the socket until

it is fully seated. If a SIP resistor network is difficult to remove

with your fingers, use a small screwdriver, prying gently first

at one end of the SIP and then the other, until it is loose.

Using the XC-3 in a simple two-way system. In many speaker

systems, a passive mid/high combination will handle the higher

frequencies, creating essentially a three-way system.

Using the XC-3 and LF-3 in a stereo three-way system

Using the SF-3 with a discrete subwoofer channel

Configuring the Accessories

+ 11 hidden pages