Personally, I would not consider replacing drivers.....work with Jonathan. Did you swap the 2 speakers to see if the reduced sound moved with the speaker? If it didn't, it's not the speaker. Do you use an AVR? If so, could you have set it up to raise/lower dbs in the left or right channel. Did you remove the grill and listen closely to each of the 3 speakers to see if it was a problem with all 3 or just one?