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[GMCnet] Speaker wiring [message #71063]

Sun, 17 January 2010 17:45

Robert McMahan

Messages: 44
Registered: February 2009

Karma: 0

Member

In checking the speaker wiring for a new radio I discovered that the ground wires for the original speakers don't seem to end up like they start out.�Do the ground wires get shared or�switched some where in the harness ? Wonder if I need to run new individual ground wires for each speaker?
�
Robert McMahan
77 Kingsley, Bozeman , MT

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Re: [GMCnet] Speaker wiring [message #71065 is a reply to message #71063]

Sun, 17 January 2010 18:28

ljdavick

Messages: 3548
Registered: March 2007
Location: Fremont, CA

Karma: -3

Senior Member

I've just wired the overhaed speakers. With a fishtape and some
fishing line I was able to get the new wires routed behind the plastic
panels and to the radio easily.

One lesson learned - to play the radio I've wired it to the house
battery by snaking a wire to the isolater through the firewall. My new
radio needs two power sources, one always on and the other switched. I
put a switch on the dash for the switched circuit so we can listen
without the ignition on.

We'll eventually play the TV audio through it as well.

Larry Davick
The Mystery Machine

Ljdavick at comcast.net

On Jan 17, 2010, at 3:45 PM, Robert McMahan <robert.montana@yahoo.com>
wrote:

> In checking the speaker wiring for a new radio I discovered that the
> ground wires for the original speakers don't seem to end up like
> they start out. Do the ground wires get shared or switched some
> where in the harness ? Wonder if I need to run new individual ground
> wires for each speaker?
>
> Robert McMahan
> 77 Kingsley, Bozeman , MT
>
>
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy

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Re: [GMCnet] Speaker wiring [message #71078 is a reply to message #71063]

Sun, 17 January 2010 19:54

RF_Burns

Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

New radios do not have a "Ground" for the speaker so to speak. There are 2 amplifiers for each speaker, one driving the + side and one driving the - side. They require a separate pair of wires for each speaker, otherwise you will let the magic smoke come out of the radio.

Mine is a 77PB and it had separate pairs already in the harness. From what I remember of the diagram in the manual (and at the time I was looking I had only up to 75 and it showed grounded speakers.

Using an ohm meter will quickly show you whether you have balanced wiring and which pair goes to which speaker. If you are not sure how to do this, you might be safer just running new pairs to each speaker.

Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

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Re: [GMCnet] Speaker wiring [message #71088 is a reply to message #71063]

Sun, 17 January 2010 23:07

zhagrieb

Messages: 676
Registered: August 2009
Location: Portland Oregon

Karma: 0

Senior Member

Robert,
Most contemporary radios insist that you NOT ground either wire to either speaker. You'll need to run a new pair to each side and keep left and right leads separate from one another.

Glenn Giere

Glenn Giere, Portland OR, K7GAG '73 "Moby the Motorhome" 26'

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Re: [GMCnet] Speaker wiring [message #71090 is a reply to message #71063]

Sun, 17 January 2010 23:38

John Ruff

Messages: 213
Registered: July 2007
Location: Chandler, AZ

Karma: 0

Senior Member

I found it much easier to purchase a 4 channel floating ground adapter. It simply connects between the new radio speaker wires and the GMC's original wiring harness. Takes no more than 2 minutes to connect and you avoid having to run new wires.

look at www.peripheralelectronics.com model fga4

Lots of other places carry them.

John Ruff

Robert McMahan wrote on Sun, 17 January 2010 16:45

John Ruff
Chandler, AZ
1975 Eleganza
WA3RIG

If I use ZDDP in a new car - will the tappets go flat?

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Re: [GMCnet] Speaker wiring [message #71110 is a reply to message #71088]

Mon, 18 January 2010 09:23

John Wright

Messages: 118
Registered: September 2008

Karma: 0

Senior Member

Depends on which year coach you have determines the if you have a floating
or common ground for the speakers or plus and minus separate wiring for each
speaker. I believe that the 77 and later coaches the wiring changed to have
a separate pair to each speaker and the earlier coaches used a common ground
wiring. I will check the wiring diagrams when I get back to the coach.

J.R. Wright
On location at Florida's space coast

On Mon, Jan 18, 2010 at 12:07 AM, Glenn Giere <glenngiere@gmail.com> wrote:

>
>
> Robert,
> Most contemporary radios insist that you NOT ground either wire to either
> speaker. You'll need to run a new pair to each side and keep left and right
> leads separate from one another.
>
> Glenn Giere
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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Re: [GMCnet] Speaker wiring [message #71111 is a reply to message #71063]

Mon, 18 January 2010 09:47

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Robert McMahan wrote on Sun, 17 January 2010 18:45

Robert,

I though that Delco gave up that foolishness in the mid 70's but I guess I am wrong there.

If there is no separate speaker return at the radio, then they are using a chassis ground. Apart from just the performance issues, there are a bunch of drawbacks to this type installation. It was "cost effective" at that level of the technology.

Are you installing new speakers at this time? If so, using the isolator mentioned may be effective, but it also may not. I will not go into the reasons here and now. If you decide to use the original grounded system, find Floating ground adapter that is "transformer isolation" and not just a big non-polar capacitor.

If you are installing a better than mediocre unit, a new pair of 16 or 18awg speaker wires is a good idea. If you take the time and effort to run a new pair for each new speaker, you will not regret taking the time later.

Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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Re: [GMCnet] Speaker wiring [message #71127 is a reply to message #71065]

Mon, 18 January 2010 13:56

larry.whisler

Messages: 356
Registered: August 2005

Karma: 8

Senior Member

I am also looking at running the television audio through the coach stereo receiver.

The problem that I have encountered is that the audio out on the flat screen tv in the coach is a digital output.

I haven't found a car stereo to allow this type of digital input.

Are there any netters out there with experience in doing this?

I have seen adapters where the digital ouput is converted to analog and then allowed to input to the receiver.

larry whisler

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Re: [GMCnet] Speaker wiring [message #71133 is a reply to message #71110]

Mon, 18 January 2010 15:58

John Wright

Messages: 118
Registered: September 2008

Karma: 0

Senior Member

I checked the wiring diagrams and GMC changed the radio wiring mid 1976
model. Early 76 and older were common or floating ground and the mid 1976
and newer have separate pairs to each speaker from the radio plug.

J.R. Wright

On Mon, Jan 18, 2010 at 10:23 AM, John Wright <powwerjon@gmail.com> wrote:

> Depends on which year coach you have determines the if you have a floating
> or common ground for the speakers or plus and minus separate wiring for each
> speaker. I believe that the 77 and later coaches the wiring changed to have
> a separate pair to each speaker and the earlier coaches used a common ground
> wiring. I will check the wiring diagrams when I get back to the coach.
>
> J.R. Wright
> On location at Florida's space coast
>
>
> On Mon, Jan 18, 2010 at 12:07 AM, Glenn Giere <glenngiere@gmail.com>wrote:
>
>>
>>
>> Robert,
>> Most contemporary radios insist that you NOT ground either wire to either
>> speaker. You'll need to run a new pair to each side and keep left and right
>> leads separate from one another.
>>
>> Glenn Giere
>> _______________________________________________
>> GMCnet mailing list
>> List Information and Subscription Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>
>
>
>
>

--
J.R. Wright
On Location at Florida Space Coast
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Re: [GMCnet] Speaker wiring [message #71151 is a reply to message #71063]

Mon, 18 January 2010 20:32

Bob de Kruyff

Messages: 4260
Registered: January 2004
Location: Chandler, AZ

Karma: 1

Senior Member

You have a floating ground which means your speakers have + and - connections. An easy way to locate your wires is to take a 9V battery and touch the radio wires. As you here a click you will find the correct wires.

Bob de Kruyff
78 Eleganza
Chandler, AZ

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