The sound of the speaker is muffled, which may be caused by the power amplifier or the speaker, which should be judged according to the specific situation. To repair this type of failure, we must first determine whether the failure is in the speaker or the amplifier.
When judging the fault, you can find a good speaker to connect to the power amplifier circuit, and then play a music signal with rich high and low bass to see if the sound of the speaker is still dull at this time? If the sound of the speaker is normal at this time, it means that the original speaker has a problem. You can disassemble the faulty speaker to see if there is a problem with the internal frequency divider circuit and whether the tweeter is damaged (you can use a multimeter to measure the DC resistance of the speaker to determine ). Common speaker failures are these problems.
If the power amplifier is connected to a good speaker, the speaker is still boring during playback, indicating that the fault lies in the power amplifier. At this point, you can check whether the position of the treble and bass knobs on the power amplifier panel is adjusted incorrectly. Sometimes the two knobs are adjusted incorrectly, and the bass boost is too much, and the treble attenuation is too much, which will cause the sound of the speaker to become muffled and lack the treble signal.
If the treble and bass knobs of the power amplifier are not adjusted incorrectly, check the power amplifier circuit. For example, the capacitance changes in the power amplifier circuit that determine the high and low frequencies will eventually affect the sound quality of the speaker. This should be checked according to the specific power amplifier circuit.