Hi my 03 coupe came with a kenwood dnx5120 installed and also has stock bose system. however i notice the sounds are weak and i cannot control the subwoofer output from my headunit.

i thought maybe the installer had the back amp wires bypassed and i had another installer open up the dash today and he found it already had the metra wires installed and connections seems ok.

so my question is that can you control your subwoofer output with aftermarket headunit?

thanks

 

No. Since the Bose amplifier is where it splits off the output to the sub and speakers, the only way to control is is by using the EQ settings.

Unless of course, you're not afraid to do a little rewiring.

Front Channels: (no change)
Headunit Line Outs -> Stock Wiring -> Bose Amp -> Stock Wiring -> Front Speakers

Rear Channels:
Headunit rear speaker outputs -> Stock Wiring -> Bypass Bose amp at rear deck -> Stock Wiring -> Rear Speakers

Subwoofer Channel:
Headunit sub outputs -> Run new wires to the bose amp -> Bose amp -> Stock Wiring -> Stock sub/6x9's.

Use the fader to balance the speakers amplified by the Bose amp and those powered by the dnx5120.
You might even notice that the rear speakers sound better since they're not ruined by the EQ'ing by the Bose amp.

 

Thanks for reply,
I asked such question because i saw another member here with 03 coupe could adjust or enable the subwoofer control out of his pioneer navi HU and stock bose combo.

rather than subwoofer problem, i think mine is suffering more of dim volume. after my research, i found my HU is 2v and not enough power for the bose 4v requirement? so i am guessing my options are either metra 7550 harness or PAC-OEM1 harness?

 

PAC-OEM1 is a much better choice, the 7550 will cause a much higher noise floor.

 

I just want to update the status to help making thread more useful

I replaced the metra 7551 wires with PAC-OEM1 harness and what a difference it makes. Before the wiring swap, I can hardly hear any sound from the rear. Now the back speakers are blasting and the 6x9 bass speakers are also pounding. However, I still cannot adjust the subwoofer output (i saw another member here with pioneer navi HU and he can adjust subwoofer output)

conclusion: My 2.2V output headunit does not work well with the oem bose system. it needs PAC-OEM1 to function properly.

 

If you're using the Bose amp, the headunit's subwoofer output isn't even connected, so any changes on the headunit won't help at all there. The Bose amp builds the subwoofer/6x9 output from the front and rear channels.