Why did the speakers begin to play quietly after a long downtime?
The sven ms-370 speakers worked perfectly, then 4 years they just stood in the house, and 1 year in the house without heating, when I connected them to the PC again, they play very, very quietly, what can be?
If it is working, then Maybe the connector just oxidized, disassemble and look. But perhaps the soldering somewhere fought off. Perform a visual inspection of the board.
There is also an option so that the potentiometer is faulty, the one that controls the volume.
The most unlikely option is that the electrolytes have dried. There can be no more reasons for such a malfunction.