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Help audio system

Discussion in 'A4/S4 forum(B5 Chassis)' started by marcodias1988, May 18, 2014.

  1. marcodias1988
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    marcodias1988 New Member

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    [May 18, 2014]
    Hi all noob here so go easy on me.
    Now got the audi a4 avant b5 1997 with a different head unit on it so as you know back speakers dont work.

    My 2 questions are whats the best way to find the back speaker cable on the loom as i just wana run 2 cables from hu to back doors for aftermarket speakers.should i cut and try everysingle cable until i get sound from speakers???
    And can anyone tell me if im running the amp cable from battery to cabin if i run it under the ecu what do i need to take apart in order to see it inside?as ive searched and seen everyone recomending that route but never say where the cable actually shows up inside ? Please help
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  3. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 18, 2014]
    The rear speakers are powered by a small amplifier in the rear. On an avant, its located in the rear left side panel in the boot along with the factory subwoofer.

    You have two choices.

    Either buy the correct lead (PC9-404) which allows you to connect the pre-outs on your head unit to this existing amplifier, and will fix the rear speakers and subwoofer.

    OR

    Run some new cable from the head units rear speaker outputs thru the car, and splice them into the rear speaker wires at the amplifier, bypassing the amplifier itself.

    cutting and trying every single cable is NOT what you want to do, find the correct cables first, THEN cut them.

    If you can get at the amp and take a decent photo of the connector and post it up, it should be possible for us to identify the speaker wires for you.


    For the power cable, you need to remove the knee bolster under the steering column. Once thats removed, if you take the lid off the ECU box and look up from the inside, you can easily see where it goes as there will be a big patch of daylight ;) Theres also a spare grommet nipple built into the ECU loom where it enters the ECU box so you dont have to hack any holes in it.
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  4. marcodias1988
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    marcodias1988 New Member

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    [May 18, 2014]
    Sory im well confused now. I wont buy the iso. So in order to find the righ cwble for the back speakers what should i do?
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  5. marcodias1988
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    marcodias1988 New Member

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    [May 18, 2014]
    By the way do you know if a 6x9 would fit the back doors?
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  6. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 18, 2014]
    Remove the rear side panel in the boot which will uncover the amp/subwoofer unit.

    Find the connector, take a photo and post it up.
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  7. marcodias1988
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    marcodias1988 New Member

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    [May 18, 2014]
    Will do in a bit later today. Need to tidy the house first :D
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  8. marcodias1988
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    marcodias1988 New Member

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    [May 18, 2014]
    Will i be able to use the amp already there to power the back speakers aftermarket. If i give it power from the battery?
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  9. Oranoco
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    Oranoco Well-Known Member

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    [May 18, 2014]
    No chance. iirc the rears are the same as the fronts and 5.25" the shelf speakers are 6.5" .
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  10. marcodias1988
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    marcodias1988 New Member

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  11. marcodias1988
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    marcodias1988 New Member

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  12. marcodias1988
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    marcodias1988 New Member

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    [May 18, 2014]
    I still cant see an amp???
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  13. marcodias1988
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    marcodias1988 New Member

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    [May 18, 2014]
    Can anyone tell me if i should drill the ecu box to let the power cable thru?its inside the car and already under ecu but cant see any holes in ecu box ... should i drill a litle one to let it out?
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  14. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 18, 2014]
    ok the amp is part of that assembly, its mounted to the rear of that alloy plate.

    If you want to make it work, just buy the ISO harness i told you about earlier, that provides it with the remote-on signal, and feeds it the audio signals it needs.

    If you carefully strip back the black tape insulation for a few inches, you should find that two pairs of the wires are sort of braided together/twisted round each other, if you find these, those are your speaker wires. If they're not twisted together, i can look up the pinout for that connector for you and find them.


    As i said above, you dont need to drill a hole. If you look at the big rubber grommet where the ECU harness leaves the ECU box and heads out into the engine bay, you'll notice a rubber nipple on it. Cut this nipple open and feed the cable thru!
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  15. marcodias1988
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    marcodias1988 New Member

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    [May 18, 2014]
    Thanks so the advice reaply helpfull. So ur basicly saying that the speakers will work if i just conect them to the 2 twisted cables behind the sub? Is that what ur saying?
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  16. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [May 19, 2014]
    Yeh, just unplug the sub box (you can remove it completely if you like), and wire the speakers into the two twisted cables.

    If the cables arent twisted, they should be:

    black/green - Left positive
    brown/red - left negative

    red/green - right positive
    brown/black - right negative

    Hopefully they're twisted though as it makes it nice and easy to identify them!
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