Hello, I have the 2004 A4 Cabriolet with Symphony Bose System without Navigation.

I purchased an Alpine Head Unit (INE-S920HD), received the appropriate METRA wiring harness and got everything wired up.

Problem is the Rear Speakers are very faint. I understand that the front door speakers are actually sub-woofers, which give volume, but not too much, while my front speakers are blasting.

My first thought was that the Head unit wasn't driving enough voltage to the Bose amp.

What am I missing? Oh, and where is the Bose Amp?

Thanks for your time.

 

The Bose amp is located in the passenger side of the trunk behind the carpet. I would expect that the Bose amp isn't going to work with your new head unit..

Even within Audi you cannot simply swap amps with another car, it has to be the same exact model #..

You might find a pin out and bypass the amp entirely , or you will have to replace the amp with a generic amp.. Which will still require some custom wiring..

On the plus side you can easily get $50-75 for your stock amp on ebay

 

I'm using an aftermarket head unit with stock amp, with no issues
Sounds really good
I added a trunk sub which helped a lot
I'm pretty sure the harness I used was metra as well

 

Thanks. Interesting thing I discovered.... The METRA wiring harness has front speakers coming out of one adapter straight to the front speaker lines and the other adapter has RCA connectors for rear/subs. It looks like the front are at speaker level, while the rear and subs are pre-amp level.

I redid the wires to use the speaker level outputs on the HU to send to the rear speaker wires, but left the subwoofer on the pre-amp output. Had to drop the source levels quite a bit, but now the front and rear are balanced.....

Notice I said "speaker wires'.... Until I can confirm that they are actually going to the Bose amp.

CrytoStorm, I'm probably going to take your advice, I think I'm just gonna ditch the amp and get a 5 channel amp and use the pre-amp outputs like they are supposed to be used.

Anyone know that max output of the speakers? Don't want to replace them, as the front is buried in the dash with tweeters on the frame.

--Ken

 

Seems that your vehicle comes with half-amplifier, front car speakers are driven by the head unit directly and rear speakers are driven by the bose amplifier.
Maybe the bose amplifier was not powered on.