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Practical Head Unit & Baffling Audio


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Just put in a Phillips CMD310 (the one that's designed for iphones, with a built in cradle and Parrot onboard) and I have to say even though I use an Android phone, the head unit is brilliant. And it was only €80!

Previous owner (henceforth referred to as Dick head) had put in a terrible Lidl style head unit with more coloured lights on the front than one of Buck Roger's mates. Dick head had also wired the speakers totally wrong and cut 6x9's into the rear bins - which I'll admit double as fairly good sub enclosures.

Anyway, I rectified the wiring and I have a respectable sound in the car. But just realised the head unit allows for only two of the three ISO plugs and my rear side door speakers aren't working. So just to test them I plugged their brown ISO plug into the socket that's normally powering the rest of the speakers via the black ISO. Anything above a very low volume distorts the two rear speakers.

I pulled the speakers to see if there was any physical damage. There isn't, but I noticed that whereas the wires that leave the ISO plug are a single + and a single -, they arrive at each terminal of the speaker as ++ and --. Somewhere in between they've multiplied.

I assume I have a Lo Line system, from the factory there is one speaker in each (side) door and a tweeter in each A pillar, and nothing under the front pass seat except the Transmission Control Unit. There is however a genuine CD changer under the drivers seat.

I don't have any spare cash for an amp right now, I just want to get the two speakers running with everything else. Any light shed or tips would be cool. Should I piggy back them on two of the 50Wx4 out of the head unit, or can I use either pair of the RCA line outs?


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It may be that you are feeding the built in amp, later discos had a head unit feeding an amp with line out levels. The amp fed everything else (and very well too!) but if you feed it speaker outs you get line buzz and distortion.

It sounds like he may have done some wiring that has made some speakers off the speaker outputs and maybe set up the others to take a sub-woofer-amp line out.

Beyond that info, I can't offer much more help, on the two heads I've dealt with lately it has had a line out to go to a ancillary amp which feeds one in the disco but doesn't feed anything in the suzuki. So you may be in look with a bit of splicing onto RCA plugs.

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Thanks lads.

I thought the impedance might have been it, but the front originals work fine from the same pins on the head output, and they seem to be identical speakers to the rear door ones.

So I came to the conclusion that the amp must still be in part of the system, except when I went looking for the amp it wasn't there. Well - from what I can tell it's supposed to be under the passenger seat, and it's not there.

Unless there's something up behind the dash, I've been over the rest of the car.


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2001 SII Td5.

It's a strange spec because I believe it was ordered with over landing in Africa in mind, but there are no rear headphone sockets so I don't believe the audio is Hi Line. If the CD unit wasn't under the drivers seat I would have said ti was Lo Line audio.

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