Blaupunkt ACAPULCO Acapulco CD51 Operating Instructions Manual page 27

Start by setting the middle and treble ranges, and finish with the bass.
Sound quality / problem
Bass too quiet
Bass sounds muddy
Booming tone
Unpleasant pressure
Tone lacks depth,
is aggressive, no stereo effect.
Muffled tone
Lack of clarity
Instruments have no brightness
Action
Boost the bass
Frequency: 50 to 100 Hz
Level: +4 to +6
Reduce lower middle tones
Frequency: 125 to 400 Hz
Level: approx. -4
Reduce middle tones
Frequency: 1,000 to 2,500 Hz
Level: -4 to -6
Boost the treble range
Frequency: approx. 12,500 Hz
Level: +2 to +4
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