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Section 1. Test and Measurement > 1.2 Electrical Testing - Pg. 2

2 SecTion | 1 Test and Measurement 1.1.1 Why Test? Sound systems must be tested to assure that all components are functioning properly. The test and measurement process can be subdivided into two major categories: electrical tests and acousti- cal tests. Electrical testing mainly involves voltage and impedance measurements made at component interfaces. Current can also be measured, but since the setup is inherently more complex it is usually calculated from knowledge of the voltage and impedance using Ohm's Law. Acoustical tests are more complex by nature, but share the same fundamentals as electrical tests in that some time varying quantity (usually pressure) is being measured. The main difference between electrical and acoustical testing is that the interpretation of the latter must deal with the complexities of 3D space, not just amplitude versus time at one point in a circuit. In this chapter we will define a loudspeaker system as a number of components intentionally combined to produce a system that may then be referred to as a loudspeaker. For example, a woofer, dome tweeter, and crossover network are individual components, but can be combined to form a loudspeaker system. Testing usually involves the measurement of systems, although a system might have to be dissected to fully characterize the response of each component. 1.2 elecTRicAl TeSTing There are numerous electrical tests that can be performed on sound system components in the laboratory. The measurement system must have specifications that exceed the equipment being mea- sured. Field testing need not be as comprehensive and the tests can be performed with less sophisticated instrumentation. The purpose for electrical field testing includes: 1. To determine if all system components are operating properly 2. To diagnose electrical problems in the system, which are usu- ally manifested by some form of distortion 3. To establish a proper gain structure