Volume stuck on high on my HT subwoofer
simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. (a) Normal connection. (b) Lost ground connection. (c) and (d) Equivalent circuits.

(a) shows the normal connection of a potentiometer. As you move the wiper closer to the ground terminal the voltage reduces. Fully anti-clockwise the audio output will be zero.

(b) If the earth tag has become disconnected then you have a variable resistor rather than a potentiometer. The equivalent circuit is shown in (c) but since R4 is going nowhere you really have (d) and the resistance varies with the position of the knob. It seems as though this has little effect on your volume.

Measure the resistance between the ends of the potentiometer. An over-range indication indicates open-circuit. You can replace the pot or try putting a resistor of about 10% of the pot value between the wiper contact and ground. This will give you some adjustment without pot replacement.