Stereo wiring & Q about early mk2 set-up

[the edmundator]

I'm wiring up a new stereo to replace the cassette unit in the GL (as much as I have enjoyed listening to a tape, the sound quality isn't great).

From memory the three wires are:

Red - power
Brown - earth
Grey/Blue - accidento bizzarro, tutto morte! (possibly electric aerial, think I've always just insulated the end and left it alone).

Is that correct?

Also, I only have old-fashioned (possibly DIN) connectors for the speakers. Although my car has always had 4 speakers wired up (all producing sound), there are only wires for two speakers. I think this is probably related to early '80s head-units only having two speaker channels (left and right), and explains why the early mk2s have a fore-aft speaker balance adjuster by the gearstick.

In this case, I presume I should just wire-up the front speaker outputs off the ISO harness from the new unit to the speaker cables in the car, and whatever magick is responsible for doing the fore/aft adjustment on the current set-up will continue to do its thing. I can't be bothered with re-wiring the speakers at this stage.

[Nate]

ideally, you should wire the speakers in 'correctly' as there is a potential for impeadance issues to upset your head unit. short term you should be fine just wiring the 2 speaker leads from your current head unit to the front channels of your new one.

[the edmundator]

The thing is, I'm fairly confident the speaker wiring is a factory installation for 4 speakers, that somehow varies the output of the left and right channels between the front and rear speakers. It's not someone's bodge job.

[ianaudia4]

I remember fitting a new stereo in my old GL back in 1988! If I remember rightly, I popped out fader control by the gearstick and made a note of the colours of the wires coming off then checked them with what was going to the speakers. It should be obvious which wires go to the head unit.
The reason that VW fitted these was because the radio/cassettes back then didn't generally have a fader control on the set, just balance.

The blue and grey wire was for illumination of the head unit and comes off the dash lighting, again this was the days when head units didn't automatically illuminate. It was also a damn sight easier to buy a quality green illuminating head unit!!!

I hope that helps Ed.

[the edmundator]

Yes, I know which wires are speakers and which are for the power/earth. I wanted to make sure it will run ok just wired up to the front speaker output from the new stereo to supply front and rear as it does at the moment. I think it will, I'll try it. If it's no good, I'll have to start taking up the carpets and running new speaker cables.

[fonzooorooo]

it's resistors in series/parallel.
if the speakers (assume 4 ohms) are in series, it'll give 8 ohms (R1+R2)... which is what you want for safety... more ohms will result in less power, but no damage...

resistors in parallel - comes out at 2 ohms for 2x4 ohms... presents a lower impedance - which is fine if your headunit is 2 ohm-stable... but chances are it's not!... and that's how you fry the amp in your headunit.

all impedance figures given for speakers are nominal, and the actual impedance whilst music is playing can drop significantly below that figure (it's frequency dependant and cabinet dependant) so you'll see the logic behind playing safe.

[the edmundator]

I find myself revisiting this issue with my 84 GTI.

I've done what I did last time and established left and right and just connected those speaker wires to the front output on the head-unit.

I think the issue fonzooorooo mentioned (it's a bit technical for me) is the reason why above a relatively low volume, the speakers click/pop frequently.

Interestingly, the fader control only has 6 wires attached to it, so I still haven't worked out exactly where all the speaker wires end up - the pair of paired wires that come out to the head-unit are different again.

I think the long and short of it is that unless you're wiring in an old early 80s stereo, the speakers need to be wired directly to the head-unit and bypassing the VW fader control.

[fonzooorooo]

^ or if you wanted to retain some functionality in the factory switch, you could probably use it as a volume control for front OR rear speakers. It's all likely to load up the amplifier though -best to do all that kind of stuff at line level, rather than speaker level. ... Especially with modern, fussy amplifiers!

If there basically aren't enough wires, I assume earths must be paired, which depending on the design of your modern headunit, it's possible it's that that it doesn't like. (if the output of the amplifier isn't actually an earth - if you see what I mean... it could "float")

[dozzum]

I removed the fader switch from my gearstick surround as it had been redundant since long before I bought the car and inserted an old leccy window switch which I wired into my electric aerial and now I have an electric aerial that I can adjust the height of, as I was getting annoyed with the two options of all the way up or nothing.