Resonance Frequency of a Speaker (INS031E)

To determine the resonance frequency of a common loudspeaker in open air, the following instruments must be used:

a) Audio generator (sinusoidal)

b) Amplifier (up to 10 W)

c) Audio Voltmeter or AC Multimeter

d) Resistor R1 with approximately 10 times the estimated impedance value for the speaker and a dissipation of at least 2 W (carbon)


The same procedure can also be used to determine the resonant frequency of the speaker in a loudspeaker enclosure.



The arrangement for the tests is shown in the figure below.






We initially set the audio generator to 1 kHz and adjust the volume of the amplifier until it reaches the point of saturation, that is, where the distortion begins to occur. Then we return the signal generator to the lower limit of the frequency band and increase the frequency while observing the multimeter's needle. This instrument should be placed on an AC scale for comfortable reading.

As we approach the resonance frequency the needle must rise, reaching the maximum point exactly at the resonant frequency. Simply read the frequency value directly on the generator scale.

One can perfectly use a function generator in place of the audio generator and an oscilloscope in place of the voltmeter, monitoring the amplitude of the obtained image.



Circuit Bench