The previous owner has installed quite a powerful audio system in the car. With 9 speakers (big and small), an amplifier, and a nice vintage style head unit.
These are the speakers in the car.
There is a big Kenwood amplifier installed at the passenger side.
I noticed that one of the speaker on the dashboard at the driver side seems to have no sound. Checking the amplifier by chance and found one of the cable is loose. I reconnected it and viola! The speaker is working now! Feel much more balanced with the speaker producing sound on the driver side now.