I can't bear the original nokia handfree of my nokia 6230i. I care very much about bass because I'm also a bass player. As I know, 6230i has a great chip for generation of music sounds with nice bass. The problem is about quality of earphones of nokia handfree. This post is to describe the process that I refited an original nokia handfree to be portable for any popular earphone.
default handfree of my nokia 6230i
Remove certain sections of plastic cover from the two ends. R side includes a red line and a gold line. L side includes a grey line and a gold line. The gold lines are ground. The lines are covered by a protection layer (so-called 銅漆, I don't know any exact english term of this). This layer can be removed by welding heater.
Attach the gold lines(grounds) together from the two sides.
Find an audio output female connector. Weld the red line to R point of an audio output female connector, also the grey line to L point and common gold line to ground point.
Pack the connector as u like.
my sony bass earphone