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View Full Version : Aftermarket HU with Bose system-** rewire or use Bose amps?



stubbs
06-02-2010, 02:32 PM
Hey guys, I've been digging around in the wiring behind my head unit (I just got this car a month ago) and discovered some interesting things. Whoever had the aftermarket unit installed did it professionally, but it looks like it was done twice. Currently, the heat unit is driving the speakers directly through custom wiring (or so it looks). I haven't pulled the door panels yet to make sure, but it looks like it was first wired to send the output (HU amped output, not pre-amp outputs) through the stock wiring, then at some point custom wires were run. However, the setup doesn't sound very good. Flat sound with no bass.

From what I've read, the best way to wire aftermarket units with the Bose system is to use the HU's pre-amp outputs and connect them to the stock Bose amps. Is that true? What are the disadvantages of running the 4-ohm head unit amp with the stock 2-ohm speakers, aside from extra stress/heat?

Another question: is there a wire going to the radio or anything back there that's powered with the accessory key position? My unit's wired to come on when the key is in the ON position, which annoys me, since I can't just listen to the radio without running the fuel pump and everything else. I probed every wire in the factory harnesses, but didn't find any that are switched with the ACC key position. I may get bored and run a wire from the ignition, but I wanted to see if anybody knows of one.

Thanks!

zergling
06-02-2010, 05:10 PM
Good luck stubbs.

I'm in a very similar situation - previous owner installed a Pioneer DEH2800MP. Now the front speakers are not running, all the sound is coming from the rear door speakers and deck subwoofers. (Unlike what I've read here folks got the fronts to run, but no power for the rears).

After several hours researching, I've just decided that I'll just run my own wires. I picked up a pair of rockford fosgates for the fronts, and plan to connect directly the HU. I'll replace the HU, amp, and rear speakers and subwoofers later on when there's a better budget.

somebody5788
06-02-2010, 05:27 PM
The OEM Bose amp is pretty nice when you have it all working right. It's best to buy the kit crutchfield sells to install a head unit.

I personally will keep my factory head unit forever and ever.

Shhmaudi
06-02-2010, 06:56 PM
I did the install on my aftermarket headunit and used the pre outs from the harness. its the way to go! My car turns on to acc.
Looks like this depending on the year:

http://www.google.com/#hl=en&q=audi+a4+harness+bose&aq=f&aqi=&aql=&oq=&gs_rfai=&fp=6f7133eec6420100

Bose amp rocks!

walky_talky20
06-02-2010, 07:38 PM
Sending pre-outs to the factory bose amp is probably the best way to get the best sound out of the factory Bose speakers. If you change the speakers, then bypassing it may be beneficial.

I'm using pre-outs to my factory Bose amp and speakers and it sounds quite good.

stubbs
06-02-2010, 08:12 PM
I did the install on my aftermarket headunit and used the pre outs from the harness. its the way to go! My car turns on to acc.
Looks like this depending on the year:

http://www.google.com/#hl=en&q=audi+a4+harness+bose&aq=f&aqi=&aql=&oq=&gs_rfai=&fp=6f7133eec6420100

Bose amp rocks!

Thanks for the link, I'll have to get one and see if it sounds better through the Bose amp.