Date: Sat, 14 Jul 2007 08:30:09 -0700
Reply-To: David Kao <dtkao0205@YAHOO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Kao <dtkao0205@YAHOO.COM>
Subject: Re: Wiring rear speakers - 86 Weekender - long
In-Reply-To: <vanagon%2007071401591537@GERRY.VANAGON.COM>
Content-Type: text/plain; charset=iso-8859-1
Mark:
There are two types of power amplifiers among car stereos. One has single ended
output, the other has differential output. Single ended has one hot wire and
a grounded one that is truly grounded to the metal chassis. For the differential
type both wires are hot and never grounded. When the signal in one swings
positively the other will swing negatively. It's like push pulling.
It is capable of much higher power output. But you can not share a common
grounded wire. Each channel (left and right, and front and rear) has to have
its own pair of wiring. Never ground (connect to metal chassis) any of the
two wires. That will cause damage to the power amplifier of the stereo.
The power transistors will burn out almost instantly.
David
--- Mark Hersh <markhersh@MSN.COM> wrote:
> The internal debate on the engine swap (Subie or diesel?) has reached an
> impasse so it seemed time to do make progress with a few little
> improvements. Some PO had removed the rear closets, and we were able to
> acquire those last year. "Monty" had AC originally but the hoses had been
> hacked off in the engine compartment and of course with no closets the
> evaporator(?) was missing. The closet we found had no AC component which
> was just as well, but had the rear stereo speakers. (remaining AC stuff has
> been removed except for the condenser).
>
> Today I removed the in-dash stereo and found four unused wires whose colors
> matched up with the wires hanging out of back end of the AC duct (the one
> above the slding door) and sure enough, a continuity check reveals they are
> the same. Great! Right and left and ground.
>
> According to Bentley and my continuity check, the ground for those speakers
> is a common ground, that is, the two wires (left and right ground) under
> the dash must be spliced together somewhere and only one wire is run
> through the duct to the back shelf, where a branch runs off for the left
> rear speaker ground.
>
> The problem is that the stereo install/operation guide (PO supplied at
> purchase) specifically warns against using a common ground for speakers and
> says that each speaker must be hooked up to the ground wire coming out of
> the plug/harness/birdsnest coming from the back of the stereo.
>
> I pulled off one of the vents and the front end of the duct work (just
> above and behind front passenger seat) and see the wire bundle heading into
> the mysterious region above the headliner. Or is that just a detour before
> it heads down the pillar between the passenger door and sliding door? I
> don't think so because I looked in some vent and also a rubber plug and saw
> no wire bundle. I didn't get underneath.
>
> First, I know nothing about car stereos. WHat would happen if I commonly
> grounded the rear speakers as did VW in 1986? Blow up the stereo or
> speakers, I imagine is the worst that could happen.
>
> Second, how in blazes do I get a single strand of 18-20 gauge wire back
> there? It wouldn't be too much trouble to get to the front end of the AC
> duct, but then between the headliner and the metal... and how down to the
> under-dash? Does that bundle run down the passenger side windshield/door
> pillar?
>
> Any suggestions/help appreciated.
>
> Mark
>
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