Crown 133472-1A User guide

1
Amplifier Application Guide
Amplifier Application Guide
© 2006 by Crown Audio®Inc., 1718 W. Mishawaka Rd., Elkhart, IN 46517-9439 U.S.A.
Telephone: [phone]. Fax: [phone].
www.crownaudio.com
Trademark Notice: Amcron®, BCA®, and Crown®, Crown Audio, IOC®, IQ System®, ODEP®and
VZ®are registered trademarks and Grounded Bridge™, PIP™ and PIP2™ are trademarks of
Crown Audio, Inc.
Other trademarks are the property of their respective owners.
133472-1A
1/06

2
Amplifier Application Guide
The information furnished in this manual does not include all of the details of design, production, or
variations of the equipment. Nor does it cover every possible situation which may arise during installa-
tion, operation or maintenance. If you need special assistance beyond the scope of this manual, please
contact our Technical Support Group.
Crown Technical Support Group
1718 W. Mishawaka Rd., Elkhart, Indiana 46517 U.S.A.
WARNING:Thisunitiscapableofproducingveryhighsoundpressurelevels.
Continuous exposure to high sound pressure levels can cause permanent
hearing impairment or loss. Caution is advised and ear protection recom-
mended when playing at high volumes.
The lightning bolt
triangle is used to alert
the user to the risk of
electric shock.
The exclamation point
triangle is used to alert
the user to important
operating or mainte-
DANGER:This amplifier can produce lethal levels of output power! Be very
careful when making connections. Do not attempt to change the output
wiring unless AC power has been removed from the amplifier for at least
TO PREVENT ELECTRIC SHOCK DO
NOT REMOVE TOP OR BOTTOM COVERS.
NO USER SERVICEABLE PARTS
INSIDE. REFER SERVICING TO QUALIFIED
SERVICE PERSONNEL.
À PRÉVENIR LE CHOC ÉLECTRIQUE
N’ENLEVEZ PAS LES COUVERCLES. IL
N’Y A PAS DES PARTIES SERVICEABLE
À L’INTÉRIEUR. TOUS REPARATIONS
DOIT ETRE FAIRE PAR PERSONNEL
QUALIFIÉ SEULMENT.
Important Safety Instructions
1) Read these instructions.
2) Keep these instructions.
3) Heed all warnings.
4) Follow all instructions.
5) Do not use this apparatus near water.
6) Clean only with a dry cloth.
7) Do not block any ventilation openings. Install in accor-
dance with the manufacturer’s instructions.
8) Do not install near any heat sources such as radiators,
heat registers, stoves, or other apparatus that produce
heat.
9) Do not defeat the safety purpose of the polarized or
grounding-type plug. A polarized plug has two blades
with one wider than the other. A grounding-type plug
has two blades and a third grounding prong. The wide
blade or the third prong is provided for your safety. If the
provided plug does not fit into your outlet, consult an
electrician for replacement of the obsolete outlet.
10) Protect the power cord from being walked on or pinched,
particularly at plugs, convenience receptacles, and the
point where they exit from the apparatus.
11) Only use attachments/accessories specified by the
manufacturer.
12) Use only with a cart, stand, bracket, or table specified
by the manufacturer, or sold with the apparatus. When a
cart is used, use caution when moving the cart/appara-
tus combination to avoid injury from tip-over.
13) Unplug this apparatus during lightning storms or
when unused for long periods of time.
14) Refer all servicing to qualified service personnel. Servic-
ing is required when the apparatus has been damaged
in any way, such as power-supply cord or plug is dam-
aged, liquid has been spilled or objects have fallen into
the apparatus, the apparatus has been exposed to rain
or moisture, does not operate normally, or has been
dropped.
Amplifier Application Guide

3
Amplifier Application Guide
Table of Contents
Introduction.................................................................................................. 4
Chapter 1: Crown Amplifiers In-Depth....................................................... 5
1.1 Rack Cooling..................................................................................... 5
1.1.1 Fan-Assisted Models................................................................. 5
1.1.2 Convection-Only Models ........................................................... 6
1.2 System Wiring ................................................................................... 7
1.2.1 Input Wiring ............................................................................... 7
Input Connector Wiring ................................................................. 7
Balanced, Grounded Source ........................................................ 7
Balanced, Floating Source ........................................................... 7
Unbalanced, Grounded Source, Twin-Lead Shielded Cable ......... 8
Unbalanced, Floating Source, Twin-Lead Shielded Cable ............ 8
Unbalanced, Grounded Source, Single-Conductor
Coax or Twisted-Pair Cable ......................................................... 8
Unbalanced, Floating Source, Single-Conductor
Coax or Twisted-Pair Cable ......................................................... 8
1.2.2 Solving Input Problems ............................................................. 9
1.3 Output Wiring .................................................................................. 10
1.3.1 Output Connector Wiring......................................................... 10
5-Way Binding Post ..................................................................... 10
Barrier Block................................................................................ 11
Neutrik®Speakon®...................................................................... 11
1.3.2 Amplifier Load Impedance ..................................................... 13
1.3.3 Determining Appropriate Speaker Wire Gauge....................... 14
1.3.4 Loudspeaker Protection .......................................................... 15
1.3.5 Solving Output Problems ........................................................ 16
High-Frequency Oscillations ....................................................... 16
Sub-Sonic Currents..................................................................... 16
1.3.6 Distributed Speaker Systems.................................................. 17
What is Constant Voltage? .......................................................... 17
Transformer Saturation................................................................ 17
1.4 Multi-way Systems (with Expansion Modules) ................................ 18
1.4.1 Active vs. Passive Crossover Networks .................................. 18
1.5 Fault Monitoring .............................................................................. 20
1.6 Setting System Gain Structure........................................................ 21
1.6.1 System Levels......................................................................... 21
1.6.2 Amplifier Level......................................................................... 21
Chapter 2: Troubleshooting ...................................................................... 23
2.1 No Power......................................................................................... 24
2.2 No Sound ........................................................................................ 25
2.3 Bad Sound ...................................................................................... 26
2.4 Amp Overheating ............................................................................ 26
Chapter 3: Glossary of Terms................................................................... 27
Appendix: Suggested Reading ............................................................... 33

4
Amplifier Application Guide
Introduction
This application guide provides useful information designed to help you best
use your new Crown®amplifier. It is designed to complement your amplifier’s
Operation Manual, which describes the specific features and specifications
of your amplifier. Helpful guides and tips on subjects such as system wiring
and system gain structure, for example, should be helpful to you whether you
are a beginner or a seasoned professional. You can choose to read this guide
from cover to cover, or if you are already familiar with Crown amps, you can
jump to specific sections as needed. A glossary of terms and list of suggested
publications for further reading are also provided for your convenience.
Please be sure to read all instructions, warnings and cautions.
For your protection, please send in the warranty registration card today. And
save your bill of sale—it’s your official proof of purchase.

Chapter 1: Crown Amplifiers In-Depth 5
Amplifier Application Guide
In This Chapter
• Rack Cooling
• System Wiring
• Amplifier Load Impedance
• Multi-Way Systems
• Distributed Speaker Systems
• Setting System Gain Structure
This chapter provides information to help you get optimum performance
from your Crown amplifier. It is a collection of techniques that can help
you avoid many of the common problems that plague sound systems. For
further study on many of these topics, refer to the recommended publications
listed in the Appendix.
1.1 Rack Cooling
When installing your Crown amp in a rack, you should take steps to make
sure that the temperature of the rack stays in a safe range. Crown amps with
fan-assisted cooling and convection-only cooling may require different tech-
niques for best performance.
When designing your rack
cooling system, you should
consider the requirements
for all mounted components.
1.1.1 Fan-Assisted
Models
If your Crown amplifier uses
fan-assisted cooling, make
sure that the front vents and/
or filters are never blocked,
and that the exhaust fan
(vented out the back or
Chapter 1
Crown Amplifiers In-Depth
Figure 1.1
Top View of Rack-
Mounted Amplifier with
Side Vents

6 Chapter 1: Crown Amplifiers In-Depth
Amplifier Application Guide
sides) is not blocked or covered by cables. Also, if your
Crown amp has foam filters, they can be cleaned with mild
dish detergent and water when needed.
The side walls of the rack should be at least 2 inches (5
cm) away from the chassis for amps with side venting as
shown in Figure 1.1.
Don’t use vented spacer panels between amps in a rack.
Because of the airflow technology we use in our amps,
it is best to stack multiple amplifiers on top of each other
with no space between.
The amplifier draws fresh air into the front of the amp
and exhausts it either out the sides and into the rack, or
out the back depending on the model. We want the hot
air that’s in the rack to vent out the sides or back—not
the front. If any of these amplifiers are spaced apart with
vented panels, some of the preheated air will recycle to
the front of the rack and back into the amplifier. The result
is loss of thermal headroom. If you choose to place the amplifiers with space
between them, then use solid panels between them, not vented panels.
You should provide adequate airflow within the rack. Additional air flow may
be required when driving low impedance loads at consistently high output
levels or for higher power models. Refer to your Crown amplifier’s Operation
Manual for detailed information on ther-
mal dissipation.
If your rack has a front door that could
block air flow to the amplifier’s air
intakes, you must provide adequate air
flow by installing a grille in the door or
by pressurizing the air behind the door.
Wire grilles are recommended over
perforated panels because they tend
to cause less air restriction. A good
choice for pressurizing the air behind a
rack cabinet door is to mount a “squirrel
cage” blower inside the rack (Option 1
in Figure 1.2). At the bottom of the rack,
mount the blower so it blows outside air
into the space between the door and in
front of the amplifiers, pressurizing the
“chimney” behind the door. This blower should not blow air into or take air out
of the space behind the amplifiers. For racks without a door, you can evacu-
ate the rack by mounting the blower at the top of the rack so that air inside the
cabinet is drawn out the back (Option 2 in Figure 1.2).
If the air supply is unusually dusty, you might want to pre-filter it using com-
mercial furnace filters to prevent rapid loading of the unit’s own air filter.
1.1.2 Convection-Only Models
When racking convection-cooled amplifiers, it is best to leave one rack-space
between amps because this type of amplifier needs space to radiate the heat.
Because of the wide range of operating
conditions your amplifer might be sub-
jected to in the field, you should con-
sider each installation independently to
ensure the best thermal performance.
If your amp starts to overheat, consider
the following possible causes:
1. Insufficient air movement.
2. Overdriving of the input stage
(severely into clip).
3. Very low-impedance loads.
4. High ambient temperatures.
Overheating
Figure 1.2
Extra Cooling with a
Rack-Mounted Blower

Chapter 1: Crown Amplifiers In-Depth 7
Amplifier Application Guide
1.2 System Wiring
The information in this section covers making input and output wiring connec-
tions, as well as troubleshooting problems relating to system wiring.
1.2.1 Input Wiring
Input Connector Wiring
Refer to the following diagrams for input cable wiring for commonly-used con-
nector types.
Note: These diagrams follow the AES wiring convention of Pin 2 = hot for XLR
connectors.
Note: If two or more channels with the same
input ground reference are driven from the
same floating source, connect only one shield
to the source chassis
Balanced, Grounded Source
For use with components equipped with three-wire
grounded AC line cord or other ground connection.
Balanced, Floating Source
For use with components equipped with two-wire
AC line cord or battery power.

8 Chapter 1: Crown Amplifiers In-Depth
Amplifier Application Guide
Unbalanced, Grounded Source,
Twin-Lead Shielded Cable
For use with components equipped with three-wire
grounded AC line cord or other ground connection.
Unbalanced, Floating Source,
Twin-Lead Shielded Cable
For use with components equipped with two-wire
AC line cord or battery power.
Unbalanced, Grounded Source, Single-
Conductor Coax or Twisted-Pair Cable
For use with components equipped with three-wire
grounded AC line cord or other ground connection.
Unbalanced, Floating Source, Single-
Conductor Coax or Twisted-Pair Cable
For use with components equipped with two-wire
AC line cord or battery power.

Chapter 1: Crown Amplifiers In-Depth 9
Amplifier Application Guide
1.2.2 Solving Input
Problems
Infrasonic (Subaudible)
Frequencies
Sometimes large infrasonic (sub-
audible) frequencies are present in
the input signal. These can damage
loudspeakers by overloading or
overheating them. To attenuate such
frequencies, place a capacitor in
series with the input signal line. The
graph in Figure 1.3 shows some
capacitor values and how they affect
the frequency response. Use only
low-leakage paper, mylar or tantalum
capacitors.
Radio Frequencies (RF)
Another problem to avoid is the
presence of large levels of radio
frequencies or RF in the input signal.
Although high RF levels may not
pose a threat to the amplifier, they
can burn out tweeters or other loads
that are sensitive to high frequen-
cies. Extremely high RF levels can
also cause your amplifier to prema-
turely activate its protection circuitry,
resulting in inefficient operation. RF
can be introduced into the signal
chain from many sources such as
local radio stations, tape recorder bias and digital signal processors (DSP). To prevent high
levels of input RF, install an appropriate low-pass filter in series with the input signal.
Some examples of unbalanced wiring for low-pass filters are shown in Figure 1.4.
For balanced input wiring use one of the examples in Figure 1.5. Filters A, B and C correspond
to the unbalanced filters above. Filter D also incorporates the infrasonic filter described previ-
ously.
Hum and Buzz
If you have noticeable hum or buzz
in your system, you may want to
check your cable connections to
see if the unwanted noise is being
introduced via a ground loop. To
determine the proper wiring, first
check whether the output from
your source is unbalanced or bal-
anced (if you don’t know, refer to
the unit’s back panel or Operation
Manual). Next, determine if the
source’s power cable is floating
(ungrounded, 2-prong) or grounded (3-prong). Finally, if the source in unbalanced, check the
type of wiring: twin-lead or single coax. Once you have determined the wiring scheme and
cable type, refer to the applicable wiring diagram in Section 1.2.1.
1. For all input connectivity, use
shielded wire only. Cables with a foil
wrap shield or a high-density braid
are superior. Cables with a stranded
spiral shield, although very flexible,
will break down over time and cause
noise problems.
2. Try to avoid using unbalanced
lines with professional equipment. If
you have no choice, keep the cables
as short as possible (see “Balanced
vs. Unbalanced” on the next page).
3. To minimize hum and crosstalk,
avoid running low-level input cables,
high-level output wires and AC power
feeds in the same path. Try to run
differing signal-cable paths at 90°
to one another. If you must use a
common path for all cables, use
a star-quad cable for the low-level
signals.
4. Before changing input connec-
tors or wiring, turn the amplifier level
controls all the way down (counter-
clockwise).
5. Before changing output connec-
tions, turn the amplifier level down
and the AC power off to minimize the
chance of short-circuiting the output.
Input Wiring Tips
Figure 1.3
Subsonic Filter Capaci-
tor Values
Figure 1.4
Unbalanced RFI Filters

10 Chapter 1: Crown Amplifiers In-Depth
Amplifier Application Guide
1.3 Output Wiring
1.3.1 Output Connector Wiring
5-Way Binding Post
If the amplifier is set for Stereo
(Dual), connect the positive (+)
and negative (–) leads of each
loudspeaker to the appropri-
ate Channel 1 and Channel 2
output connectors as shown in
Figure 1.6.
If the amplifier is set for Bridge-Mono (if equipped), con-
nect a mono load across the red binding posts of each
channel as shown in Figure 1.7. Do NOT use the black
binding posts when the amp is set for Bridge Output.
Notice that the Channel 1 red binding post is positive
(+) and the Channel 2 red binding post is negative (–).
If amp is set for Parallel-Mono (if equipped), connect
a 14-gauge or larger jumper between the Channel 1
and Channel 2 Positive terminals, then connect a mono
load to the Channel 1 binding posts as shown in Figure
1.8. Do NOT use the Channel 2 binding posts when the
amp is set for Parallel Output. Caution: Never short or
parallel the output channels of an amplifier to itself
or to any other amplifier.
Figure 1.5
Balanced RFI Filters
A balanced audio circuit will have both
positive (+) and negative (–) legs of
the circuit that are isolated from the
ground circuit. These balanced legs
exhibit identical impedance character-
istics with respect to ground, and may
also carry the audio signal at the same
level, but with opposite polarities. This
results in a line that offers excellent
rejection of unwanted noise.
On the other hand, an unbalanced
circuit usually holds one leg at ground
potential, while the second leg is “hot.”
Unbalanced line is less expensive, but
is much more susceptible to noise, and
is not normally used in professional
applications. For the cleanest signal,
with less hum and buzz, a balanced
line is always recommended. It is espe-
cially helpful if you have a long cable
run (over 10 feet (3 m)), since noise is
easily introduced into long, unbalanced
lines.
Balanced vs. Unbalanced
Figure 1.6
5-Way Binding Post
Wiring for Stereo
Figure 1.7
5-Way Binding Post
Wiring for Bridge-Mono
Figure 1.8
5-Way Binding Post
Wiring for Parallel-
Mono

Chapter 1: Crown Amplifiers In-Depth 11
Amplifier Application Guide
Barrier Block
If the amplifier is set for Stereo (Dual), connect the positive (+) and negative (–) leads
of each loudspeaker to the appropriate Channel 1 and Channel 2 output connectors
as shown in Figure 1.9.
If the amplifier is set for
Bridge-Mono (if equipped),
connect a mono load across
the positive terminals of each
channel as shown in Figure
1.10. Do NOT use the nega-
tive terminals when the amp
is set for Bridge Output.
If the amplifier is set for Parallel-Mono (if
equipped), connect 14-guage or larger
jumper between the Channel 1 and Channel
2 Positive terminals, then connect a mono
load to the Channel 1 positive and negative
terminals as shown in Figure 1.11. Do NOT
use the Channel 2 terminals when the amp
is set for Parallel Output. Caution: Never
short or parallel the output channels of an
amplifier to itself or to any other amplifier.
Figure 1.9
Barrier Block Wiring for
Stereo
Figure 1.10
Barrier Block Wiring for
Bridge-Mono
1. To prevent possible short circuits,
wrap or otherwise insulate exposed
loudspeaker cable or cable connectors.
2. Do not use connectors that might
accidentally tie conductors together
when making or breaking the connec-
tion (for example, a standard, 1/4-inch
stereo phone plug).
3. Never use connectors that could
be plugged into AC power sockets.
Accidental AC input will be an electri-
fying experience for your equipment.
But you will find out real quick if your
speakers are any good at 60 Hz!
4. Avoid using connectors with low cur-
rent-carrying capacity, such as XLRs.
5. Do not use connectors that have
any tendency to short.
Output Wiring Tips Neutrik®Speakon®
To assemble the Neutrik Speakon NL4FC connector, complete
the following steps:
1. Slide the bushing (E) and chuck (D) onto the end of the cable
as shown in Figure 1.12.
Note: Your NL4FC connector kit should contain both a black
and a white chuck. Use the white chuck for cable with a diam-
eter of 0.25 to 0.5 inch (6.35 to 12.7 mm). Use the black chuck
for cable with a diameter of 0.375 to 0.625 inch (9.525 to
15.875 mm).
2. Strip approximately 3/4-inch (20-mm) of casing from the cable
end. Strip approximately 3/8-inch (8-mm) from the end of each
of the conductors down to bare wire (C).
3a.Insert each wire into the top of appropriate slot of the connec-
tor insert (B) as shown in Figure 1.13. Use a (1.5-mm) allen
wrench or flat blade screwdriver to tighten the side connecting
screws.
Figure 1.11
Barrier Block Wiring for
Parallel-Mono

12 Chapter 1: Crown Amplifiers In-Depth
Amplifier Application Guide
3b.If the Mode switch is
in the “Stereo” posi-
tion (for stereo con-
figuration), connect
the positive (+) and
negative (–) leads
of each wire to the
appropriate Chan-
nel 1 and Channel
2 connectors as
shown in Figure
1.14.You may use all 4 poles of the Channel 1 output
connector to feed both speakers, if you wish.
3c.If the Mode switch is in the “Bridge” position (for
mono configuration), connect the load across the
positive (+) terminals of the connector as shown
in Figure 1.15. For Bridge-Mono Mode, non-invert-
ing output, Ch1+ is the positive (+) and Ch2+ is the
negative (–).
3d. Never short or parallel the output channels of
an amplifier to itself or any other amplifier.
4. Slide the connector insert (B) into the connector
hous-
ing (A),
making
sure that
the large
notch on
the outer
edge of the
insert lines
up with the
large groove on the inside of the con-
nector housing. The insert should slide
easily through the housing and out the
other side until it extends approximately
3/4-inch (19-mm) from the end of the
housing, as shown in Figure 1.16.
5. Slide the chuck (D) along the cable and
insert into the housing, making sure
that the large notch on the outer edge
of the chuck lines up
with the large groove
on the inside of the
connector housing.
The chuck should
slide easily into the insert/hous-
ing combination until only
approximately 3/8-inch (9.5-mm)
of the chuck end extends from
the back end of the connector
as shown in Figure 1.17.
Figure 1.15
Bridge-Mono Output
Wiring
Figure 1.16
Connector Assembly:
Insert into Connector
Housing
Figure 1.17
Connector Assembly:
Chuck into Connector
Housing
Figure 1.12
Order of Assembly for
the Neutrik Speakon
NL4FC Connector
Figure 1.13
Wiring for the Neutrik
Speakon NL4FC
Connector
Figure 1.14
Stereo Output Wiring

Chapter 1: Crown Amplifiers In-Depth 13
Amplifier Application Guide
To connect the Speakon plug into the mating connector on the speaker, line
up the notches between the insert and the mating connector, then insert the
plug and turn one quarter-turn clockwise as shown in Figure 1.19. The thumb-
lock on the housing will snap into the locked position when the connector is
properly seated.
1.3.2 Amplifier Load Impedance
A major consideration when matching amplifiers with speakers is the resulting
impedance presented to the amplifier when speakers are connected to the
output. The impedance of the load, in part, determines how much power the
amplifier will produce. Also, too low of impedance can cause the amplifier to
overheat.
Impedance is much like resis-
tance, except impedance
changes with frequency. Imped-
ance and resistance are both
measured in ohms. To under-
stand the effect of impedance
in an electrical circuit, consider
the following analogy: a wire is
much like a water pipe. Elec-
trical current is like the water
flowing through the pipe. Imped-
ance’s role is that of the valve.
The valve resists or impedes
(hence the terms) the flow of
water through the pipe. If the
valve is opened (less imped-
ance), water flows freely. As
the valve is turned toward the
closed position (more imped-
ance), the flow of water slows.
As the amplifier drives lower
impedances, it produces more
current, thus more power.
6. Slide the bushing along the cable
and screw onto the end of the
connector combination as shown
in Figure 1.18. Note that the
bushing features a special lock-
ing construction which will prevent
disassembly of the NL4FC con-
nector once this cap is tightened
into place. Before tightening, you
may want to test the connector in
a live system to make sure it has
been assembled properly.
Figure 1.18
Connector Assembly:
Bushing onto Connector
Housing Assembly
Figure 1.20
Series Speaker
Impedances
Figure 1.21
Parallel Speaker
Impedances
Figure 1.19
Connecting the
Speakon plug to the
mating connector

14 Chapter 1: Crown Amplifiers In-Depth
Amplifier Application Guide
Each speaker has an impedance
rating, typically 4 or 8 ohms. Connect-
ing one 8-ohm speaker to an amplifier
channel presents an 8-ohm impedance
to the channel.
If two or more speakers are wired to
the same channel, the net impedance
presented to the channel will be either
more or less than one of the speakers alone, depending on whether they
were wired in series or in paral-
lel (see Figures 1.20 and 1.21).
When speakers are wired in
series, the net impedance pre-
sented to the amp is the sum
of the individual impedances.
When wired in parallel, the net
impedance becomes less than
the impedance of one of the
speakers, as calculated with the
following formula:
You can use the table in Figure
1.22 to find the net impedance
for many common speaker
combinations.
Note: for best results, do
not wire speakers of differ-
ing impedances (one 4 ohm
and one 8 ohm for example)
together.
If two 8-ohm speakers are wired
in series, they form one 16-ohm
load for the amplifier, since
impedances add when speak-
ers are wired in series. If, on the
other hand, the same 8-ohm
speakers are wired in paral-
lel, they form one 4-ohm load
for the amplifier. The 4-ohm
load will cause the amplifier to
produce much more power than
the 16-ohm load, and much
more waste heat as well.
secnadepmIlellaraP
srekaepSmhO4srekaepSmhO8
rekaepS1mhO4mhO8
srekaepS2mhO2mhO4
srekaepS3mhO3.1mhO7.2
srekaepS4mhO1mhO2
Figure 1.22
Parallel Impedance
Chart
Figure 1.23
Wire Size Nomograph.

Chapter 1: Crown Amplifiers In-Depth 15
Amplifier Application Guide
1.3.3 Determining Appropriate Speaker Wire Gauge
You should choose loudspeaker cables with sufficient gauge (thickness)
for the length being used. The resistance introduced by inadequate loud-
speaker cables will reduce both the output power and the motion control of
the loudspeakers. The latter problem occurs because the damping factor
decreases as the cable resistance increases. This is very important because
the amplifier’s excellent damping factor can easily be negated by insufficient
loudspeaker cables.
Use the nomograph in Figure 1.23 and the procedure that follows to find the
recommended wire gauge (AWG or American Wire Gauge) for your system.
1. Note the load impedance of the loudspeakers connected to each channel
of the amplifier. Mark this value on the “Load Impedance” (A) line of the
nomograph.
2. Select an acceptable damping factor and mark it on the “Damping Factor”
(B) line. Higher damping factors yield greater motion control over the
loudspeakers, and therefore lower distortion. A common damping factor for
commercial applications is between 50 and 100. Higher damping factors
may be desirable for live sound, but long cable lengths often limit the high-
est damping factor that can be achieved practically. In recording studios
and home hi-fi, a damping factor of 500 or more is very desirable.
3. Draw a line through the two points with a pencil, and continue until it inter-
sects the “Source Resistance” (C) line.
4. On the “2-Cond. Cable” (D) line, mark the required length of the cable run.
5. Draw a pencil line from the mark on the “Source Resistance” line through
the mark on the “2-Cond. Cable” line, and on to intersect the “Copper Wire”
(E) line.
6. The required wire gauge for the selected wire length and damping factor is
the value on the “Copper Wire” line. Note: Wire size increases as the AWG
gets smaller.
7. If the size of the cable exceeds what you want to use, (1) find a way to use
shorter cables, (2) settle for a lower damping factor, or (3) use more than
one cable for each line. Options 1 and 2 will require the substitution of new
values for cable length or damping factor in the nomograph. For option
3, estimate the effective wire gauge by subtracting 3 from the apparent
wire gauge every time the number of conductors of equal
gauge is doubled. So, if #10 wire is too large, two #13
wires can be substituted, or four #16 wires can be used for
the same effect.
1.3.4 Loudspeaker Protection
Crown amplifiers generate enormous power. If your loud-
speakers don’t have built-in protection from excessive
power, it’s a good idea to protect them. Loudspeakers are
subject to thermal damage from sustained overpowering
and mechanical damage from large transient voltages.
Special fuses can be used to protect your loudspeakers in
both cases.
Depending on the application, you may
want to use a PIP™ module to protect
your loudspeakers (for PIP-compatible
amps only). When properly configured, all
PIP modules with signal-driven compres-
sion can provide loudspeaker protection.
For more information on available PIP
modules with signal-driven compression,
contact your Crown dealer or check the
current selection of PIP modules at www.
PIPs for Speaker Protection

16 Chapter 1: Crown Amplifiers In-Depth
Amplifier Application Guide
Two different types of fuses are
required for thermal protection
and voltage protection. Slow-blow
fuses are usually selected to
protect loudspeakers from thermal
damage because they are similar
to loudspeakers in the way they
respond to thermal conditions
over time. In contrast, high-speed
instrument fuses like the Littlefuse
361000 series are used to protect
loudspeakers from large transient
voltages. The nomograph in Figure
1.24 can be used to select the
properly rated fuse for either type
of loudspeaker protection.
There are basically two
approaches that can be taken
when installing fuses for loud-
speaker protection. A common
approach is to put a single fuse
in series with the output of each
channel. This makes installa-
tion convenient because there is only one fuse protecting the loads on each
output. The main disadvantage of this approach becomes obvious if the fuse
blows because none of the loads will receive any power.
A better approach is to fuse each driver independently. This allows you to
apply the most appropriate protection for the type of driver being used. In
general, low-frequency drivers (woofers) are most susceptible to thermal
damage and high-frequency drivers (tweeters) are usually damaged by large
transient voltages. This means that your loudspeakers will tend to have better
protection when the woofers are protected by slow-blow fuses and high-fre-
quency drivers are protected by high-speed instrument fuses.
1.3.5 Solving Output
Problems
High-Frequency Oscillations
Sometimes high-frequency oscillations occur which can cause your amplifier
to prematurely activate its protection circuitry and result in inefficient opera-
tion. The effects of this problem are similar to the effects of the RF problem
described in Section 1.2.2. To prevent high-frequency oscillations:
1. Lace together the loudspeaker conductors for each channel; do not lace
together the conductors from different channels. This minimizes the
chance that cables will act like antennas and transmit or receive high fre-
quencies that can cause oscillation.
2. Avoid using shielded loudspeaker cable.
3. Avoid long cable runs where the loudspeaker cables from different ampli-
fiers share a common cable tray or cable jacket.
Figure 1.24
Loudspeaker Fuse
Nomograph

Chapter 1: Crown Amplifiers In-Depth 17
Amplifier Application Guide
4. Never connect the amplifier’s
input and output grounds together.
5. Never tie the outputs of multiple
amplifiers together.
6. Keep loudspeaker cables well
separated from input cables.
7. Install a low-pass filter on each
input line (similar to the RF filters described in Section 1.2.2).
8. Install input wiring according to the instructions in your amplifier’s Opera-
tion Manual.
Sub-Sonic Currents
Another problem to avoid is the
presence of large sub-sonic currents
when primarily inductive loads are
used. Examples of inductive loads
are 70-volt transformers and electro-
static loudspeakers.
Inductive loads can appear as a
short circuit at low frequencies. This
can cause the amplifier to pro-
duce large low-frequency currents
and activate its protection circuitry.
Always take the precaution of install-
ing a high-pass filter in series with
the amplifier’s input when inductive
loads are used. A 3-pole, 18-dB-
per-octave filter with a –3 dB fre-
quency of 50 Hz is recommended
(depending on the application, an
even higher –3 dB frequency may be
desirable).
Another way to prevent the amplifier
from prematurely activating its protection systems and to protect inductive
loads from large low-frequency currents is to connect a 590 to 708 µF nono-
larized capacitor and 4-ohm, 20-watt resistor in series with the amplifier’s
output and the positive (+) lead of the transformer. The circuit shown in Figure
1.25 uses components that are available from most electronic supply stores.
1.3.6 Distributed Speaker Systems
Multiple-speaker systems for paging and background music systems are
common in such facilities as schools, restaurants, industrial facilities offices
and retail. In these systems, many speakers are distributed throughout the
facility, often across long distances, making them difficult and expensive to
implement with traditional, direct low-impedance amplifiers. A less expensive
and more reliable method is the distributed speaker system.
A distributed speaker system consists of an amplifier or amplifier channel
driving one or more speakers with transformers connected to a pair of wires
called a “home run.” The transformers step the line voltage down to a lower
Figure 1.25
Inductive Load (Trans-
former) Network
Figure 1.26
Typical Distributed
Speaker System

18 Chapter 1: Crown Amplifiers In-Depth
Amplifier Application Guide
level to drive the speaker, and are connected across the
wires (see Figure 1.26). The combination of transformer
and speaker line presents a much higher impedance to the
amplifier than would the speaker itself, making it possible to
add many speakers to a single home run.
In distributed speaker systems, as the ratio of voltage to
current become greater, less power is lost on the home run.
This makes it possible to use much smaller gauge wire for
home runs than would otherwise be possible.
What is Constant Voltage?
“Constant-voltage” amplifiers do not, in fact, supply a con-
stant output voltage. The audio is represented with varying
voltage just as with a low-impedance amplifier. The term
“constant-voltage” was arrived at for two reasons. First, con-
stant-voltage amplifiers produce their maximum power when
the output voltage reaches the specified value. For example,
an amplifier rated at 200 watts, when set to 70V output, will
produce 200 watts when the output voltage reaches 70V.
Second, the output voltage of an amplifier driving a con-
stant-voltage (distributed) speaker run remains constant
across a wide range of impedances.
Transformer Saturation
It’s important to know that transformers can easily become “saturated” at low-frequencies. Transformer saturation
occurs when the magnetic field created by the signal content becomes too much for the core of the transformer to
handle. This condition can be dangerous to the amplifier, and can also cause distortion.
An effective way to prevent step-down transformer saturation is to filter the very low-frequency content from the
audio.Your amplifier may provide high-pass filters for this purpose (see your Operation Manual). If not, see Sec-
tion 1.2.2 for filter suggestions.
1.4 Multi-way Systems
(with Expansion Modules)
This section shows how multi-way systems can be effectively designed using optional expansion modules that
feature active crossover networks. Example systems are shown for single and multiple amp two-way systems and
three-way systems.
The range of frequencies present in full-range music is wider than most any single speaker component can accu-
rately reproduce. Because of this, most professional speaker systems employ two or more speaker components
to do the job. Crossover networks (or crossovers) are electrical circuits that divide an incoming signal into two
or more separate frequency bands. The separate bands are then routed to speakers designed to reproduce the
range of frequencies they are being fed.
1.4.1 Active vs. Passive Crossover Networks
There are two types of crossovers: active and passive. Passive crossover networks are located in the signal chain
between the amplifier and speakers. The networks built into speaker cabinets are typically passive. The primary
advantage to passive crossovers is that they use fewer amplified channels. The primary disadvantage is that they
work with amplified or high-voltage signals because of being located after the amplifier in the signal chain,
causing them to waste much of the power before it gets to the speakers. They also have lower dynamic
range.
Active crossovers are typically located before the amplifier in the signal chain. They work with lower “line-level”
signals, meaning they waste much less power.
You can use amps without constant-volt-
age settings on distributed speaker sys-
tems if the power output is high enough.
For example, an amplifier rated for 78
watts output into 8 ohms will directly drive
a 25-volt line. To calculate the necessary
power for driving a specific voltage line
use the following formula:
where P equals the necessary power
output,
V equals the voltage of the distributed
speaker system, and R equals the imped-
ance of the amplifier for the power specifi-
Using Low-Impedance

Chapter 1: Crown Amplifiers In-Depth 19
Amplifier Application Guide
Figure 1.27
Typical Single-Amp,
Stereo, Two-Way
Hookup
Figure 1.28
Typical Two-Amp,
Bridge-Mono, Two-Way
Hookup

20 Chapter 1: Crown Amplifiers In-Depth
Amplifier Application Guide
Figure 1.29
Typical Three-Amp,
Bridge-Mono,
Three-Way Hookup
Figure 1.30
Fault Status External
Circuit Design
When you use an active crossover to split the power drive to the loudspeaker
components, you gain a wide range of advantages, including:
1. Increased gain because the insertion loss of passive crossover networks is
eliminated.
2. Consistent power bandwidth: power bandwidth is changed in multi-way pas-
sive systems if transducers change impedance or vaporize (blow up).
3. Levels can be matched
more accurately to the
components.
4. Improved dynamic
range.
Active crossovers for
Crown amps are available
in both PIP and SST mod-
ules (see your Operation
Manual for details about
available options for your amplifier).
Figures 1.27 through 1.29 illustrate typical systems using active crossover
modules.