hello, i'm looking into building a test bench to be able to test the output of an amp, i've got a amp meter, 400A DC power supply, and access to all kinds of resistors, my question is i was told to use a non-inductive resistor, why is that? a speaker is a inductive coil so wouldn't that change the output? i'm also wondering if i would use a inductive resistor in stead?
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Tri County KustomZ
certified installer
The real-world load on an amplifier is quite different from a non-inductive resistor that often is used as an amplifier load in a test laboratory. In reality, the load typically is a loudspeaker system that has impedance that changes significantly over the audio spectrum. When you look at a typical loudspeaker impedance curve, you will see a significant deviation from the “nominal” impedance rating of the device.
Because of this fact, there have been several attempts over the years to define a standardized test load that emulates the type of load that a loudspeaker would provide to an amplifier, but it seems without general acceptance. Most “lab” amplifier testing is done with non-inductive load resistors. It is difficult to obtain high-power non-inductive load resistors, so most high-power amplifiers are tested with wire-wound resistors of one type or another, including some rather creative loads using hot water heater elements, electric stove elements, pizza ovens, etc. Several examples of this type of creative effort can be found at
https://srforums.prosoundweb.com/index.php/m/0/5094/16/0.
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Generally, a non-inductive resistor is a harder load on an amplifier anyhow. So, if you use that, you should be safe with an inductive speaker load.
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What is normal anyway???