Quoted from Triggerfish:Found it. Thanks. I've never touched it before so I wonder why it would have suddenly changed volume on its own. It's back to normal now though so thanks again.
I had this exact same thing happen on my Space Shuttle too, where it sounded like all the bass dropped out and the sound was super quiet. A tiny turn of the volume knob brought it back up to full sound. (I keep it at relatively low volume.) My guess was perhaps enough vibration over time may have turned the knob ever so slightly.