I just finished installing Alpine CDE-103BT head unit on my S2000
This head unit was build-in bluetooth product so I tried connecting my iphone 4 into the head unit. I tried the call through bluetooth after connecting to it, but how can I listen to music by bluetooth? Everything was connected but I could not listen to music

 

you need A2DP(aka stereo bluetooth) support to stream music over bluetooth which your headunit doesnt support, it only supports hands free for answering phone calls.

 

Alpine is king of nickel and dime. Like RagnaRok said, you probably need ANOTHER module to get that to work.

P.S. Just so you don't think I am ragging on Alpine, everything electronic in my car is Alpine.

 

So what exactly is a2dp? I searched on google and it seems like a software or just a program, how do I get this for stream audio?

 

A2DP is basically one of the many bluetooth profile protocols which happens to be used for streaming music over bluetooth. the most familiar of the bluetooth profiles of course is Hands Free which is the profile used for handling phone calls over bluetooth. theres whole range of bluetooth profiles for handling different tasks such as transferring files wirelessly(OBEX) or connecting online through a dial up network(DUN)

now as to whether or not you can make your headunit support A2DP, i really have no idea. it could be as simple as software or there may be hardware limitations. honestly its probably more trouble than its worth.

im not very knowledgeable with Alpine but from what i can find on their site it looks like you need the KCE-400BT module to make it work.

 

You don't "get it". It's either a feature of your head unit or it isn't. If it's a must have then you need to make sure the head unit supports it before you make your purchase -- not after.

From http://www.alpine-usa.com/product/view/cde-103bt/Specs
Note how A2DP is not listed. The handsfree and headset profiles are only for phone calls.

If you want A2DP with this head unit then your best bet is to add a BT audio gateway and to wire it to the AUX in on your head unit. If I needed A2DP and I was in your boat, I'd probably return the head unit and look for a better suited one.

The Alpine BT modules are generally mentioned on the specs or accessories page for a given head unit on Alpine's site if they are compatible with the head unit. I doubt that any of them are compatible with the OP's head unit but the OP can call Alpine to verify.

 

You're ragging on Alpine, but they deserve it.

 

new line up alpine radios will have built in blue tooth.