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1
Amplifi er Application Guide
®
© 2006 by Crown Audio Inc., 1718 W. Mishawaka Rd., Elkhart, IN 46517-9439 U.S.A.
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Amplifi er Application Guide
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2 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. DANGER: This amplifi er can produce lethal levels of output pow
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3 Table of Contents Introduction .................................................................................................. 4 Chapter 1: Crown Amplifi ers In-Depth ....................................................... 5 1.1 Rack Cooling ..................................................................................... 5 1.1.1 Fan-Assisted Models ................................................................. 5 1.1.2 Convection-Only Models ................................
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4 Introduction This application guide provides useful information designed to help you best ® use your new Crown amplifi er. It is designed to complement your amplifi er’s Operation Manual, which describes the specifi c features and specifi cations of your amplifi er. 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 c
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Chapter 1: Crown Amplifi ers In-Depth 5 Chapter 1 Crown Amplifi ers In-Depth In This Chapter � Rack Cooling � System Wiring � Amplifi er Load Impedance � Multi-Way Systems � Distributed Speaker Systems � Setting System Gain Structure his chapter provides information to help you get optimum performance Tfrom your Crown amplifi er. 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, ref
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6 Chapter 1: Crown Amplifi ers In-Depth sides) is not blocked or covered by cables. Also, if your Crown amp has foam fi lters, they can be cleaned with mild Overheating dish detergent and water when needed. Because of the wide range of operating The side walls of the rack should be at least 2 inches (5 conditions your amplifer might be sub- cm) away from the chassis for amps with side venting as jected to in the fi eld, you should con- shown in Figure 1.1. sider each installation independen
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Chapter 1: Crown Amplifi ers In-Depth 7 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. Balanced, Grounded Source Balanced, Floating Source For use with
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8 Chapter 1: Crown Amplifi ers In-Depth Unbalanced, Grounded Source, Unbalanced, Floating Source, Twin-Lead Shielded Cable Twin-Lead Shielded Cable For use with components equipped with three-wire For use with components equipped with two-wire grounded AC line cord or other ground connection. AC line cord or battery power. Unbalanced, Grounded Source, Single- Unbalanced, Floating Source, Single- Conductor Coax or Twisted-Pair Cable Conductor Coax or Twisted-Pair Cable For use with components
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Chapter 1: Crown Amplifi ers In-Depth 9 1.2.2 Solving Input Input Wiring Tips Problems Infrasonic (Subaudible) 1. For all input connectivity, use to one another. If you must use a Frequencies shielded wire only. Cables with a foil common path for all cables, use wrap shield or a high-density braid a star-quad cable for the low-level Sometimes large infrasonic (sub- are superior. Cables with a stranded signals. audible) frequencies are present in spiral shield, although very fl exible
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10 Chapter 1: Crown Amplifi ers In-Depth Balanced vs. Unbalanced 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 us
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Chapter 1: Crown Amplifi ers In-Depth 11 Barrier Block If the amplifi er 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. Figure 1.9 If the amplifi er is set for Barrier Block Wiring for Bridge-Mono (if equipped), Stereo 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
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12 Chapter 1: Crown Amplifi ers In-Depth 3b. If the Mode switch is Figure 1.12 in the “Stereo” posi- Order of Assembly for tion (for stereo con- the Neutrik Speakon fi guration), connect NL4FC Connector 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 Figure 1.13 connector to feed both speakers, if you wish. Wiring for the Neutrik Speakon NL4FC 3c. If
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Chapter 1: Crown Amplifi ers In-Depth 13 6. Slide the bushing along the cable Figure 1.18 and screw onto the end of the Connector Assembly: connector combination as shown Bushing onto Connector in Figure 1.18. Note that the Housing Assembly 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 Figure 1.19 a live system to make sure it h
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14 Chapter 1: Crown Amplifi ers In-Depth Each speaker has an impedance Parallel Impedances Figure 1.22 rating, typically 4 or 8 ohms. Connect- 4s Ohm Speakers 8 Ohm Speaker Parallel Impedance ing one 8-ohm speaker to an amplifi er Chart channel presents an 8-ohm impedance 1m Speaker4m Oh 8 Oh to the channel. 2m Speakers2m Oh 4 Oh If two or more speakers are wired to 3m Speakers1m .3 Oh 2.7 Oh the same channel, the net impedance 4m Speakers1m Oh 2 Oh presented to the channel will be either
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Chapter 1: Crown Amplifi ers In-Depth 15 1.3.3 Determining Appropriate Speaker Wire Gauge You should choose loudspeaker cables with suffi cient 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 amplifi er’s excellent damping fa
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16 Chapter 1: Crown Amplifi ers In-Depth Two different types of fuses are Figure 1.24 required for thermal protection Loudspeaker Fuse and voltage protection. Slow-blow Nomograph 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.
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Chapter 1: Crown Amplifi ers In-Depth 17 4. Never connect the amplifi er’s Figure 1.25 input and output grounds together. Inductive Load (Trans- 5. Never tie the outputs of multiple former) Network amplifi ers together. 6. Keep loudspeaker cables well separated from input cables. 7. Install a low-pass fi lter on each input line (similar to the RF fi lters described in Section 1.2.2). 8. Install input wiring according to the instructions in your amplifi er’s Opera- tion Manual.
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18 Chapter 1: Crown Amplifi ers In-Depth level to drive the speaker, and are connected across the wires (see Figure 1.26). The combination of transformer Using Low-Impedance and speaker line presents a much higher impedance to the amplifi er than would the speaker itself, making it possible to You can use amps without constant-volt- add many speakers to a single home run. age settings on distributed speaker sys- tems if the power output is high enough. In distributed speaker systems, as
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Chapter 1: Crown Amplifi ers In-Depth 19 Figure 1.27 Typical Single-Amp, Stereo, Two-Way Hookup Figure 1.28 Typical Two-Amp, Bridge-Mono, Two-Way Hookup Amplifi er Application Guide
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20 Chapter 1: Crown Amplifi ers In-Depth Figure 1.29 Typical Three-Amp, Bridge-Mono, Three-Way Hookup 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 match
