As I bought always cheaper earphones, they're often destroyed at once.
Today Left speaker hasn't worked.
I decided to buy more expensive earphone and went to a electrical appliances shop whose name is Bic Camera.
They sells a lot of products, cellphone, smart-phone, PC, audio device, game and etc.
I usually buy a earphone at convenience store, so I can easily select what I buy.
Because they have only one or two earphones.
However at the camera shop I couldn't quite decide what I should buy in large amount of those.
Since it's passed about an hour, I decided a reimporting model of JVC.
It's a lower sound better than usual one.