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The output pattern of an industrial loudspeaker shown using spherical polar plots taken at six frequencies. Loudspeaker measurement is the practice of determining the behaviour of loudspeakers by measuring various aspects of performance.
A minimum acceptable resistance value is usually specified (typically in the mega ohm (MΩ) range per circuit tested). Multiple circuits having a common return may be tested simultaneously, provided the minimum allowable resistance value is based on the number of circuits in parallel. Five basic isolation test configurations exist: [3]
Analog multimeter Digital multimeter. A multimeter (also known as a volt-ohm-milliammeter, volt-ohmmeter or VOM) [1] is a measuring instrument that can measure multiple electrical properties. [2] [3] A typical multimeter can measure voltage, resistance, and current, [4] in which case can be used as a voltmeter, ohmmeter, and ammeter.
Sixteen ohm drivers (or loudspeakers systems) would be connected to the 16-ohm tap, 8 ohm to the 8 ohm tap, etc. This is significant since the ratio between the loudspeaker impedance and the amplifier's impedance at a particular frequency provides damping (i.e., energy absorption) for the back EMF generated by a driver.
First, the meter needs to be zeroed by shorting the measurement points together and performing an adjustment for zero ohms indication prior to each measurement. This is because as the battery voltage decreases with age, the series resistance in the meter needs to be reduced to maintain the zero indication at full deflection.
The Lindos sequence test system is now a 'de facto' standard [citation needed] in broadcasting and many other areas of audio testing, with over 25 different segments recognized by Lindos test sets, and the EBU standard is no longer used.
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This standard is voluntary, and many 8-ohm drivers have resistances of ≈5.5 ohms, and proportionally lower for lower rated impedances. Measured in henries (H), this is the inductance of the voice coil. The voice coil is a lossy inductor, in part due to losses in the pole piece, so the apparent inductance changes with frequency.