123734.5.1.9.2 Improperly Wired ac Receptacles..................................................... 1302
34.5.1.9.3 Two-Wire ac Receptacles............................................................ 1302
34.5.1.9.4 Older Two-Wire Audio Equipment.................................................... 1303
34.5.1.9.5 Grounding for Safety Outdoors....................................................... 1303
34.5.1.9.6 Grounding to Reduce External Noise Pickup............................................ 1304
34.5.1.9.7 Definitions: Ground, Earth, Common.................................................. 1304
34.5.1.9.8 Ground Loops in Unbalanced Systems................................................. 1304
34.5.1.9.9 Ground Loops in Balanced Systems and Using the Telescoping Shield Connection.............. 1304
34.5.1.9.10 The Pin 1 Problem................................................................ 1305
34.5.1.9.11 Transformers versus Active Balanced Inputs and Outputs................................. 1305
34.5.1.9.12 Using Proper Shielding to Reduce Noise Pickup......................................... 1306
34.5.1.9.13 Reducing Noise Pickup from ac Lines................................................. 1306
34.5.1.9.14 More Tips on Reducing Noise Pickup................................................. 1306
34.5.2 Testing and Adjusting................................................................ 1307
34.5.2.1 Signal Delay in Sound Reinforcement............................................... 1307
34.5.2.1.1 Signal Delay for Loudspeaker Clusters................................................. 1307
34.5.2.1.2 Signal Delay for an Under-Balcony Distributed System.................................... 1307
34.5.2.1.3 Signal Delay for a Loudspeaker or Loudspeaker Cluster................................... 1307
34.5.2.2 Equalization.................................................................... 1307
34.5.2.2.1 The Concept of Equalization......................................................... 1307
34.5.2.2.2 What Equalization Can and Cannot Do................................................. 1308
34.5.2.2.3 System Design Criteria for Equalization................................................ 1308
34.5.2.2.4 System Equipment................................................................. 1308
34.5.2.2.5 Test Equipment.................................................................... 1308
34.5.2.2.6 The Test Setup.................................................................... 1309
34.5.2.2.7 The Equalization Process............................................................ 1309
34.5.2.2.8 The Desired System Response Curve.................................................. 1310
34.5.2.2.9 Why High-Frequency Roll-Off Is Required in Equalization................................. 1310
34.5.2.2.10 Use of High- and Low-Pass Filters................................................... 1310
34.5.2.2.11 Equalization Using TEF or Other Equipment That Measures Direct Sound Response............ 1311
34.5.2.2.12 Use of Narrow-Band Filters in Equalization............................................ 1311
34.5.2.2.13 Equalization Using Source-Independent Measurement (SIM).............................. 1312
34.5.2.2.14 Automatic Equalization............................................................ 1312
34.5.3 Rigging the Cluster.................................................................. 1312
34.5.4 System Documentation............................................................... 1312
34.5.4.1 Original Plans and As-Built Drawings............................................... 1314
34.5.4.2 Equipment Lists and Equipment Owner’s Manuals..................................... 1314
34.5.4.3 Software Configurations and Backups............................................... 1314
34.5.4.4 Approvals and Certifications....................................................... 1314
34.5.4.5 Additional Documentation........................................................ 1314
34.5.5 Troubleshooting a Sound System....................................................... 1314
34.5.5.1 Know the Block Diagram......................................................... 1314
34.5.5.2 Logical Troubleshooting.......................................................... 1314
34.5.5.3 DSP Troubleshooting............................................................ 1315
34.5.5.4 Anticipating and Preparing for Problems............................................. 1317
34.6 Applications.......................................................................... 1317
34.6.1 Portable and Tour Sound Systems....................................................... 1317
34.6.1.1 Packaging...................................................................... 1317
34.6.1.2 Loudspeaker Systems............................................................ 1317
34.6.1.3 Portable System Rigging.......................................................... 1318