Some speaker labels display an actual, measured impedance for a specific listed impedance. To give you an idea of what these frequencies mean, most bass tracks fall between 90 and 200 Hz, while “chest thumping” sub bass can be as low as 20 Hz. The midrange, including the majority of non-percussion instruments and voices, covers 250 Hz to 2kHz. [1] X Research source

If there is only one setting for resistance, your multimeter is auto-ranging, and will find the correct range automatically. Too much DC current can damage or destroy the voice coil of a speaker. The risk is low here, since most multimeters only produce a small current. [2] X Research source

Do not remove any wires connected directly to the speaker cone.

The majority of loudspeakers have a nominal impedance of 4, 8, or 16 ohms. Unless you get a strange result, it’s safe to assume your speaker has one of these impedance values for the purpose of pairing it with an amplifier.

If you are new to audio tests or DIY electronics, consider audio testing tools that connect to a computer. These are often less accurate, but novices may appreciate the auto-generated graphs and data.

Some amps produce inconsistent voltage at low frequencies, which is a common source of inaccuracy in this test. For best results, check with the voltmeter to make sure the voltage stays constant as you adjust the frequency using the sine wave generator. Use the highest quality multimeter you can afford. The inexpensive models tend to be less accurate for the measurements later in this test. It may help to purchase higher quality multimeter leads at an electronics store. [4] X Research source www. sbacoustics. com/index. php/download_file/-/view/191/

100W amp: 2. 7k Ω resistor rated to at least 0. 50W 90W amp: 2. 4k Ω, 0. 50W 65W amp: 2. 2k Ω, 0. 50W 50W amp: 1. 8k Ω, 0. 50W 40W amp: 1. 6k Ω, 0. 25W 30W amp: 1. 5k Ω, 0. 25W 20W amp: 1. 2k Ω, 0. 25W

For example, if the resistor has a measured resistance of 1230 ohms, and the voltage source is 10 volts, the current I = 10/1230 = 1/123 amps. You can leave this as a fraction to avoid rounding errors.

You can use an oscilloscope instead of a voltmeter. In this case, find the voltage associated with the greatest amplitude.

For example, if I = 1/123 amps and the voltmeter measures 0. 05V (or 50mV), then Z = (0. 05) / (1/123) = 6. 15 ohms.