Cinema Accessories
for DCA Series amplifiers
U S E R M A N U A L
▼ XC-3
▼ LF-3
▼ SF-3
Two-way crossover with delay
Low-frequency filter with delay
Subwoofer filter
*TD-000079-00*
TD-000079-00 rev. B
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
Illustrations: Setup flow chart, XC-3 front and rear, delay and crossover SIP
selection charts, SIP identifier chart, and HF boost response curve.
LF-3
Setting up the LF-3....................................................................8
Factory-installed SIPs..........................................................9
Factory switch settings.........................................................9
Recommended amplifier settings......................................9
Illustrations: Setup flow chart, LF-3 front and rear, delay and crossover SIP
selection charts, SIP identifier chart.
SF-3
Setting up the SF-3....................................................................10
Factory-installed SIPs.........................................................11
Factory switch settings.........................................................11
Recommended amplifier settings......................................11
Illustrations: Setup flow chart, SF-3 front and rear, low-pass/high-pass SIP
selection chart, SIP identifier chart.
MOUNTING TO AMPLIFIER...............................................12
APPLICATION EXAMPLE......................................................................13
WARRANTY INFORMATION.........................................14
HOW TO CONTACT QSC AUDIO PRODUCTS ....................15
3
INTRODUCTION & DESCRIPTION OF EACH MODEL
Introduction
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
accessoryincludesanassortmentoftheproperSIPresistornetworksandthreemountingscrews. KeeptheunusedSIPsforfutureuse.
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 apass-through output in
parallelwiththeinputfordistributing the audio signal to the LF-3. The filter circuitry uses a 4th-order Linkwitz-Riley alignment
with 24 dB/octave slopes.
LF-3
UsedinasystemwiththeXC-3, theLF-3performsthelow-frequencycrossoverfunctionsina3-waysystemasshown, opposite
page, bottom-right.UnliketheXC-3, ithastwodiscrete 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:switchedon,itprovidesa6dBbumpattheselectedhigh-passfrequency,usefulforextendingthelow-endresponse
ofsomespeakersystems;off,theresponseisaflatButterworthcurvethatis3dBdownattheselectedfrequency.Theoutput
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 programfromfull-rangeaudio, as shown, opposite page, bottom-left. Itcan
also be used with a discrete subwoofer channel in cinema sound systems.
4
CONFIGURING THE ACCESSORIES
Configurable functions of the three accessory models
Configuring the Accessories
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, changinginputoroutputconnections, ordetachingthe
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
flowchartforeachmodelwillhelpyouproperlyconfigurethe
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
itisfullyseated.IfaSIPresistornetworkisdifficulttoremove
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 and LF-3 in a stereo three-way system
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 SF-3 with a discrete subwoofer channel
5
XC-3
Setting up the XC-3
Setup flowchart for the XC-3
Setting up the XC-3
Setting up the XC-3 requires setting the DIP switches and
selecting/inserting SIP resistors into the appropriate sockets.
DIP switches #2, #9, and #10 must be set to the ON position
(default settings for the XC-3). The flowchart below takes you
through all the steps necessary before mounting the accessory
to the amp.
Theillustrationbelowshowsthelocationsofthesocketsforthe
SIPresistornetworks. TheSIPresistornetworkscanbeinserted
either way, as long as each network pin goes into its own hole
inthesocket.Straightenthepins,ifneeded,beforeinsertingthe
SIP into its receptacle.
Use the tables on the following page to select the correct
resistor networks for the settings you need. The SIPs supplied
with the XC-3 provide a selectable frequency range for fXO of
80 Hz to 1.5 kHz, and delay settings from 0.3 to 1.8 milliseconds;
contact QSC’s Technical Services Group if your application
requires different settings.
When using the XC-3 in a three-way system in conjunction with
the LF-3, the lower frequency (fHP) should match the crossover
frequencyoftheLF-3(fXO).TheSIPssuppliedwiththeXC-3allow
a selectable frequency range for fHP of 80 to 500 Hz.
XC-3 Factory-installed SIPs
fXO
500 Hz (12 kW SIP resistor in J1)
1.8 milliseconds (27 kΩ SIP resistor in J2)
80 Hz (68 kΩ SIP resistor in J7)
LF delay
fHP
XC-3 controls,
switches, and SIP
socket locations
6
XC-3
Setting up the XC-3
XC-3 Factory Switch Settings
When shipped from the factory, the DIP switch settings should be set as follows:
Switches 7 & 8 ON:
sets XC-3 to Biamp mode
Switch 1 ON:
activates LF delay
Switches 3 through 6 OFF: HF boost disabled
Switches 2, 9, and 10 ON: Factory default settings for proper operation.
XC-3 Recommended Amplifier Settings
Clip limiters: ON (both channels)
Lowfrequencyfilters:ON(bothchannels),selecteither30
or 50 Hz roll-off, depending on speaker specifications
(both channels)
Operating mode: stereo
Use these tables to determine the
Identifying SIP resistor networks
correct resistor values for the crossover
frequencies and delays you need. The
shaded values are for the high-pass
frequency (fHP) of the XC-3.
Crossover freq. (fXO
)
SIP resistor value
80 Hz
150 Hz
200 Hz
250 Hz
300 Hz
350 Hz
400 Hz
500 Hz
600 Hz
650 Hz
800 Hz
1 kHz
68K
39K
27K
22K
20K
18K
15K
12K
10K
8.2K
6.8K
5.6K
4.7K
3.9K
Delay (ms)
SIP resistor value
1.8
1.4
1.3
1.2
1
27K
22K
20K
18K
15K
12K
10K
8.2K
6.8K
5.6K
4.7K
0.8
0.7
0.6
0.5
0.4
0.3
1.2 kHz
1.5 kHz
Effects of high frequency boost on
frequency response (crossover
frequency = 500 Hz). A boost of +10 dB
is most common for compensating for
screen loss (attenuation of high
frequencies as sound passes through
screen perforations).
7
LF-3
Setting Up the LF-3
Setting up the LF-3
Setup flowchart for the LF-3
SettinguptheLF-3requiressettingtheDIPswitchesand
selecting/inserting SIP resistors into the appropriate
sockets. DIP switches #2 and #4 through #9 must be set
to OFF, and switch #3 set to ON (factory default for
properoperation).Theflowchart,right,takesyouthrough
the steps necessary before mounting the accessory to
the amp.
TheLF-3istypicallyusedinasysteminconjunctionwith
the XC-3 crossover. For example, a stereo three-way
system will require three DCA amplifiers, two XC-3’s,
and one LF-3. The typical input signal is full-range audio
taken from the XC-3’s male XLR connector labeled
“OUTPUT (TO LF-3)”.
Theillustration, below, showsthelocationsofthesock-
etsfortheSIPresistornetworks. Theresistornetworkscanbeinsertedeitherway, aslongaseachpingoesintoitsownreceptacle.
Straighten pins, if needed, before inserting the SIP into its receptacle.
Use the tables on the following page to select the correct resistor networks for the crossover frequency (fXO) and delay settings you
need. The SIPs supplied with the LF-3 provide a range of frequency selections from 80 Hz to 500 Hz, and delay settings from 0.3
to1.8milliseconds;delaycanbebypassedbyputtingSwitches1and10intheOFFposition.ContactQSC’sTechnicalServicesGroup
if your application requires different settings.
When using the LF-3 in a three-way system in conjunction with the XC-3, the crossover frequency of the LF-3 (fXO) should match the
lower high-pass frequency (fHP) of the XC-3.
In most circumstances, the LF-3 would be used with an amplifier in stereo mode. But if two amp channels are needed for one low
frequency signal, you can use the Input 1 connector of the LF-3 and parallel the inputs of the amplifier. Amplifier inputs can be
paralleled using the amplifier’s DIP switches (mode switches).
LF-3 controls,
switches, and SIP
socket locations
8
LF-3
Setting Up the LF-3
LF-3 Factory-installed SIPs
fxo
350 Hz, both channels (18 kΩ SIP resistor installed in J6 and J8)
Delay
1.4 milliseconds, both channels (22 kΩ SIP resistor installed in J1 and J2)
LF-3 Factory Switch Settings
When shipped from the factory, the DIP switch settings should be set as follows:
Switch 1 and Switch 10 ON:
Switch 2 and Switches 4 through 9 OFF: Required default setting for proper operation of the LF-3
Switch 3 ON: Required default setting for proper operation of the LF-3
Delay active (both channels)
LF-3 Recommended Amplifier Settings
Clip limiters: ON, (both channels)
Low-frequency filters: ON (both channels), select either 30 or 50 Hertz roll-off depending on speaker specifications (both channels)
Operatingmode:TypicallyStereomode, butParallelmodecanbeusedinapplicationsrequiringdualLFampchannelswithonesource
Identifying SIP resistor networks
Use these tables to determine the
Delay (ms)
SIP resistor value
correct resistor values for the crossover
frequencies and delays you need.
1.8
1.4
1.3
1.2
1
27K
22K
20K
18K
15K
12K
10K
8.2K
6.8K
5.6K
4.7K
Crossover freq. (fXO)
SIP resistor value
80 Hz
150 Hz
200 Hz
250 Hz
300 Hz
350 Hz
400 Hz
500 Hz
68K
39K
27K
22K
20K
18K
15K
12K
0.8
0.7
0.6
0.5
0.4
0.3
9
SF-3
Setting up the SF-3
Setting up the SF-3
Setting up the SF-3 requires setting the DIP switches, and
selecting/insertingSIPresistorsintotheappropriatesockets.
DIP switches #1 through #6 and #10 must be set to OFF
(factory default for proper operation). The flowchart, right,
takes you through all the steps necessary before mounting
the accessory to the amp.
The illustration below shows the locations of the two SIP
sockets on the SF-3. The resistor networks can be inserted
either way, as long as each pin goes into its own receptacle.
Straighten pins, if needed, before inserting the SIP into its
receptacle.
The mono subwoofer program can be derived from summing
and filtering stereo or mono full-range audio or it can come
fromadiscretemonosubwooferchannel,suchasina5.1,6.1,
or 7.1 cinema surround system. If the subwoofer program is
tobederived,usetheSF-3’slow-passfiltertosetthehighendofthesubwooferpassband.Ifthesubwooferprogramsourceisadiscrete
channel, as in most cinema systems, we recommend you bypass the low-pass filter.
Use the table, opposite page, to select the correct resistor networks for the SF-3’s filter frequency settings. The SIPs supplied provide
a selection of three low-pass frequencies: 80, 150, and 250 Hz; and six high-pass frequencies from 20 to 50 Hz. Use the speaker
manufacturer’s recommended filter settings.
The low-frequency boost switch selects the Q of the high-pass filter: 0.707 for flat (Butterworth), or 2 for “boost,” which adds a 6 dB
peak at the filter’s selected frequency.
SF-3 controls,
switches, and SIP
socket locations
10
SF-3
Setting Up the SF-3
SF-3 Factory-installed SIPs
fHP= 30 Hz (27 kΩ SIP resistor in J2)
fLP= 250 Hz (22 kΩ SIP resistor in J6)
SF-3 Factory Switch Settings
When shipped from the factory, the DIP switch settings should be set as follows:
Switches 1 through 6 and Switch 10 OFF: Default setting for SF-3
Switches 7 & 8 ON: Low-pass filter off (“cinema” setting)
Switch 9 OFF: LF flat
SF-3 Recommended Amplifier Settings
Clip limiters ON (both channels)
High-pass filter OFF (both channels)
Operating mode: Stereo or Bridge mode, as the application requires
Use this table to determine the correct
resistor values for the SF-3 filter frequencies.
Identifying SIP resistor networks
Low-pass freq. (fLP)
SIP resistor value
80 Hz
150 Hz
250 Hz
68K
39K
22K
High-pass freq. (fHP
)
SIP resistor value
20 Hz
25 Hz
30 Hz
35 Hz
40 Hz
50 Hz
47K
33K
27K
20K
15K
10K
11
MOUNTING- All Models
Mounting the Accessories
An accessory may be mounted with the amplifier either in or out
of the rack, even if the amp is installed with rear rack ears.
1. Turn off the amplifier before installing the accessory.
2. Make sure the SIP resistor networks are installed properly and no SIP sockets
are empty.
3. LineuptheHD-15connectorontheaccessorywiththeamplifier’sDataPort,then
press the accessory onto the back of the amplifier so that the HD-15 connector
inserts into the DataPort.
4. Use the three screws supplied to secure the accessory to the amplifier
chassis, as shown below. Two long screws go into the holes near the
DataPort, while the short screw goes through the hole in the tab on the right
edge of the accessory. Do not overtighten the screws.
5. Attach the input and output cables to the appropriate connectors on the
accessory.Usetheamplifier’snormaloutputconnectorsforattachingspeaker
and monitor cabling.
12
APPLICATION EXAMPLE- Setting Up in the Cinema Sound System
Setting up the DCA Accessories in the Cinema Sound System
Setting up the DCA accessories in the B chain of the cinema sound system primarily involves setting the trim
levels on the XC-3, LF-3, and SF-3. This requires the cinema processor’s internal pink noise generator and an
acoustical real-time spectrum analyzer.
1. Set up the analyzer microphone in the center of the cinema audience seating area
or in another recommended location.
2. Set the all DCA amplifiers’ gain controls to maximum.
3. Route the pink noise test signal from the cinema processor to the left channel XC-
3 input. Observe the frequency response on the spectrum analyzer and use the HF
trim control on the XC-3 and the LF trim on the LF-3 to balance the levels of their
frequency bands to that of the mid-frequency band, within specifications. If the
shape of the HF response is not correct, use a boost setting that better corrects the
deficiency; turn the amplifiers off before changing the switch settings.
4. Repeat this process for the center and right screen channels and any surround
channels that are bi- or tri-amped.
5. Followtheprocessorinstructionsforsettingsoundpressureleveloutputsofallthe
channels, including the subwoofer.
If you are unable to obtain a satisfactory frequency response or SPL on a channel, carefully check the wiring
and connections. Some likely causes are reversed speaker polarity on one or more drivers, loose or broken
wiring or connections, or blown or damaged speaker drivers.
A typical 6.1 surround system with DCA amplifiers and LF-3, SF-3, and XF-3 cinema accessories
13
MAINTENANCE AND WARRANTY
Cleaning
QSC Audio Products 3 Year Limited Warranty
The faceplate and chassis can be cleaned with a soft cloth and
nonabrasive, noncorrosive, mild cleaning solution. Products like
Simple Green and Windex work well. Do not use powders or
scrubbing pads of any type as they are usually abrasive and will
permanentlydamagethefinishofyourcinemaaccessory. Dampen
a soft, lint-free cloth with the cleaning solution and wipe the
accessory gently. Ensure that cleaning solution does not get down
into the connectors. Do not spray the solution directly onto the
accessory as it will penetrate into the connectors.
QSCAudioProducts, Inc. (“QSC”)guaranteesitsproductstobefree
from defective material and / or workmanship for a period of three
(3) years from date of sale, and will replace defective parts and
repair malfunctioning products under this warranty when the de-
fect occurs under normal installation and use - provided the unit is
returned to our factory or one of our authorized service stations via
pre-paid transportation with a copy of proof of purchase (i.e., sales
receipt). This warranty provides that the examination of the return
productmustindicate,inourjudgment,amanufacturingdefect. This
warranty does not extend to any product which has been subjected
to misuse, neglect, accident, improper installation, or where the
date code has been removed or defaced. QSC shall not be liable for
incidentaland/orconsequentialdamages. Thiswarrantygivesyou
specific legal rights. This limited warranty is freely transferable
during the term of the warranty period.
User Maintenance
There is no user-level maintenance on the LF-3, SF-3, or XF-3.
Contact QSC’s Technical Services Group if service is required.
Warranty Information
If the cinema accessory isn’t working properly, please
verify the accessory’s DataPort connector is properly
seated on the amplifier and that all retaining screws are
tight. If proper operation can not be restored, the acces-
sory may require service. This must be performed by
qualified service personnel. To obtain the location of you
nearest QSC Authorized Service Center, please contact
you QSC dealer or contact QSC’s Technical Services Group.
Customer may have additional rights, which vary from state to
state.
Intheeventthatthisproductwasmanufacturedforexportandsale
outside of the United States or its territories, then this limited
warranty shall not apply. Removal of the serial number on this
product, or purchase of this product from an unauthorized dealer,
will void this limited warranty.
Disclaimer
Periodically, this warranty is updated. To obtain the most recent
version of QSC’s warranty statement, please visit
QSC Audio Products, Inc. is not liable for any damage to speakers,
amplifiers, or any other equipment that is caused by negligence or
improper installation and/or use of the LF-3, SF-3, or XF-3. Due to
the possibility of the user installing a SIP resistor improperly or of
an incorrect value, QSC Audio Products, Inc. is not liable for any
direct or indirect damage caused by improper SIP installation or
value selection.
Contact us at 800-854-4079 or visit our website at
one sent to you. This warranty does not cover shipping damage
caused by improper packing or the use of improper shipping
cartons.
14
HOW TO CONTACT QSC
WORLD WIDE WEB:
TELEPHONE NUMBERS:
Main Number
+1 (714) 754-6175
Sales Direct Line +1 (714) 957-7100
or (800) 854-4079 toll free (U.S.A. only)
Technical Services (714) 957-7150
or (800) 772-2834 toll free (U.S.A. only)
FACSIMILE (FAX) NUMBERS:
Sales & Marketing FAX
Technical Services FAX
+1 (714) 754-6174
+1 (714) 754-6173
ADDRESS:
QSC Audio Products, Inc.
1675 MacArthur Boulevard
Costa Mesa, CA 92626-1468 USA
15
© Copyright 1998, 2002 QSC Audio Products, Inc. All rights reserved.
“QSC” and the QSC logo are registered with the U.S. Patent and Trademark Office.
QSC Audio Products, Inc., 1675 MacArthur Boulevard Costa Mesa, California 92626 USA
PH: (714) 754-6175 FAX: (714) 754-6174
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