Ipod, GPS, speaker problem/question

[BadLt]

I got the Kuryakan Sound of Chrome speakers for my iPod. I also got a Zumo 550 GPS. Now for the speakers to work, they come with the male end the earphone jack. I hooked them up to a power supply in the house and I'm very happy with the sound. Now in order to hear the turn by turn directions from the GPS to plug them into an external speaker.
So I go to Radio Shack, buy a felmale/female coupler and a Y adapter. With the coupler, I plug the male in from the speakers in, then the male ends from the GPS and Ipod. The GPS dominates the musice from the Ipod. If the GPS isn't making any sound, the music is still low. I reverse the cords with the smae results. I unplug the cord from the GPS and the music gets a little louder but not as loud as if they were plugged directly into the Ipod.
Is there something I am doing wrong? Can it be possible to have the music play with the GPS hooked up? Do I need to hardwire the GPS into the speaker wire? I really would like to hear the directions without loosing the music. And no, bluetooth is not an option because I hate those ear pieces. I do not/refuse to wear them... Pluse I wear a half helmet so it'll just blow off...
Thanks for any help.
Tim

[AngryHatter]

Sounds like either impedence issues or maybe the Y adapter?

Is the Y adapter a stereo adapter?
If not you're always going to have that unless you hardwire them

If I am understanding this correctly.

[PainterD]

I've found that you can have those kind of problems will mixing different brands and types of electronics. I would just get a small separate speaker for your GPS and hook it up separate from the radio speakers. I assume the GPS is made to over power the other speakers when it's turned on and might do some damage to the other system over time.