Nuvi 650 - Unite english voice file with mandarin voice file - question

 

hi
i just got my Garmin 650 few weeks ago
i am having lots of fun
changing POI and pictures

lately i am trying to put different voice languages on my garmin 650
searching on the net i found that 660 is avaliable in Taiwan. and i was able to find a file for mandarin speaking voice file.
someone already converted for North american version.
so i was able to use the mandarin voice on my 650 no problem, but it is not TTS, meaning it will tell you turn right or left, numbers or Km, but it is not able to tell you the street ahead.

so i am trying to play around with englsh and asian voice file.

online i found a program that you can split the voice file and convert it to WAV, it work on asian voice file.
but i would get an error if i try to split on the english voice TTS file.

so my question is anyone know what other program can split the VPM(TTS) voice files, so i can convert them to WAV

i am thinking to convert all them to WAV
then overwrite the english voice WAV to mandarin WAV, leaving the rest in English

would that work?
anyone have advice?
thanks