I woke up around noon. I decided to repair Victor's unit. One unit works ok. I compared both units to check up the faulty condition. Two wires in surface attaches cone paper and the wires in faulty unit seems to come out. I repaired it and suddenly generated sound surprised me while repairing. I found the main reason was incomplete connection. I soldered it and painted it black . Finally it worked properly and I set it to the baffle board when it became dry.
I changed RCA speaker to hand-made speaker made of zelkova tree, but the sound was almost same. It seems that the sound speed is slow with 16 cm and I'm satisfied with it. I put away RCA speaker in closet. It sounds like movie theater when this speaker is connected to TV or amplifier. The sound quality is quite different from AV amplifier of 5.1 channel. 5.1 channel has powerful sound and it is suitable to watch war movie. I think 2 channel is better. Why don't you try both of them?