Originally Posted by
Bozanimal
Reduced volume in one speaker is usually due to one of three things:
1 - "Balance" needs to be adjusted at the amplifier
2 - Faulty connection
3 - Amplifier failure
This is a physical problem, not a software problem. Updated drivers will not help. You've already done some investigation - and a good job, too - and it's definitely not a "balance" issue. Since it occurs regardless of which speaker you plug in, it's definitely a problem on the amplifier side. You can try bending the RCA cables slightly by crimping them a hair, to see if a tighter connection yields and improvement, but I very much doubt this is the issue. I'm guessing that there is a loose connection inside somewhere, such as a loose solder point or possible a short, and it is likely not able to be easily identified and fixed.
Your best bet is to contact the manufacturer and replace them, though given the price I'm guessing it'd be almost silly to pay shipping to RMA them. I would say your best options are to either live with the unbalanced speakers and enjoy them at the volumes of which they are capable, or replace them.
Good luck,
Boz