A capacitor marked "104" is 0.1μF or 100nF. If the woofer is 8 ohms then this capacitor in series will pass only frequencies of 200kHz and higher that you cannot hear. If you connect the capacitor parallel with the woofer then you will not hear any difference than without the capacitor.
Your said, "make clear sound". Why is the sound not clear? Distortion, hum or buzz? Woofer does not produce low frequency sounds loud enough?
Again I am asking, "What is the diameter of the woofer speaker and what impedance and power rating does it have?"
Is it in an enclosure designed for its detailed spec's?
Does your amplifier feed it low frequencies?