Speaker wiring

[ree.eric]

Installing a new radio and wondering if there are ways around the 1 wire to speakers and the common chassis ground. Do I have to run new wires? Where
do the original speakers ground wires attach to the chassis.
--
Eric & Ree '74 ex-Sequoia (parts) '75 Eleganza (TB, exhaust x-over blocking plates, Manny reaction arms and discs, 3"exhaust rear muffler, aux vacuum,
fuel tank sealing, rebuilt senders and new rubber, propane hot water heater.) Alexandria, Ontario, Canada

 

[G&Rs66]

I just got done installing a JVC cassette head unit with 12 disc changer I
had an adapter from my 75 Cadillac that takes and plugs right into the GMC
wiring if you're taking out the original 8-track you can buy these kits at
Walmart just look for the year GM product and don't worry about the ground
wire I did not use anything other than the original wires and mine works
great

> Installing a new radio and wondering if there are ways around the 1 wire
> to speakers and the common chassis ground. Do I have to run new wires? Where
> do the original speakers ground wires attach to the chassis.
> --
> Eric & Ree '74 ex-Sequoia (parts) '75 Eleganza (TB, exhaust x-over
> blocking plates, Manny reaction arms and discs, 3"exhaust rear muffler, aux
> vacuum,
> fuel tank sealing, rebuilt senders and new rubber, propane hot water
> heater.) Alexandria, Ontario, Canada
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[RF_Burns]

Yes you should worry about "one side grounded" speakers. Earlier model radios used single-ended amplifiers. Each side (right and left) had one
amplifier driving one side of the speaker with the return being ground.

Newer radios use 2 amplifiers per side with each amplifier driving one wire of the speaker. This is known as a bridge amplifier. As one amp is
driving positive voltage, the opposite amplifier is driving negative (180 degrees out of phase). This gave the effect of twice the voltage across the
speaker giving 4 times the audio power available to each speaker.

At zero volume an audio amplifier is sitting at 1/2 the supply voltage (about 6.5 volts). If this was connected through a speaker to ground there
would be several amps of DC flowing through the speaker and both the speaker and amplifier would burn out. However for the earlier singled-ended
amplifiers, a capacitor was placed in series with the speaker output to block this DC voltage while passing the AC (Audio voltage) through to the
speaker.

With bridged amplifiers, both sides of the speaker see this 1/2 supply voltage so there is no DC voltage across the speaker. This allowed the
elimination of the output capacitors saving costs and improving the low end (bass) frequency response of the amplifier. So on a new bridged amplified
radio there is 6.5 volts DC on all the speaker leads and connecting them to a grounded speaker system will cause much DC current flow and smoke will
result.

If you really must connect a bridged amplifier to a grounded speaker, you must install a capacitor in series with the radio output. Use a 1000uf
16volt or higher electrolytic capacitor. Wire the negative lead of the capacitor towards the speaker. Use only the positive lead of each channel and
insulate (tape) the others off. There are pre-made adapters available that have these DC blocking capacitor built-in.

Be aware you will now only get about 1/4 of the audio power the radio is rated for.

So if you have grounded single wire speakers, just run a pair of wires to each speakers. Note the polarity markings on the speakers and keep the
polarity consistent for best "sound reproduction"

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
Hubler 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

 

[johnny]

Actually, for the nerds, a dual power supply amplifier usually has one output side grounded, although it may only be at audio ground which will create
some problems if it isn't isolated. For several which can use one wire, look here:

https://www.google.com/search?q=audio+amplifier+schematic&tbm=isch&imgil=xwtwli01Pc-mZM%253A%253BAxS70cb2JRZaJM%253Bhttp%25253A%25252F%25252Fwww.satsleuth.com%25252FSchematics.aspx%25253FCategory%2525253DAmplifiers&source=iu&pf=m&fir=xwtwli01Pc-mZM%253A%252CAxS70cb2JRZaJM%252C_&usg=__2uZAhJq6Gv3skgfbalbUzkA1ViM%3D&biw=1920&bih=971&ved=0ahUKEwiI2NDB54jVAhXFez4KHU9iCKoQyjcIQg&ei=rL1oWYjSKcX3-QHPxKHQCg=uUTCjNlB0LlzMM:&imgrc=xwtwli01Pc-mZM:

Which isn't to say you shouldn't follow the maker's instructions for your radio, most of which want you to isolate the speaker leads. Both of them.

--johnny

n.b. for the true nerds, note that a failure of an output device will put the power supply across the speker in these confiogurations. Normally
there's a safety circuit which senses for zero DC at the output before the audio and speakers are connected internally. - jb

--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[jim kanomata1]

​he later units have a ground side already wired.​

> I just got done installing a JVC cassette head unit with 12 disc changer I
> had an adapter from my 75 Cadillac that takes and plugs right into the GMC
> wiring if you're taking out the original 8-track you can buy these kits at
> Walmart just look for the year GM product and don't worry about the ground
> wire I did not use anything other than the original wires and mine works
> great

>
> > Installing a new radio and wondering if there are ways around the 1 wire
> > to speakers and the common chassis ground. Do I have to run new wires?
> Where
> > do the original speakers ground wires attach to the chassis.
> > --
> > Eric & Ree '74 ex-Sequoia (parts) '75 Eleganza (TB, exhaust x-over
> > blocking plates, Manny reaction arms and discs, 3"exhaust rear muffler,
> aux
> > vacuum,
> > fuel tank sealing, rebuilt senders and new rubber, propane hot water
> > heater.) Alexandria, Ontario, Canada
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502

 

[johnny]

The later units pretty much all use a hybrid IC amplifier as opposed to discrete components. Higher power stuff also has a bipolar power supply at
higher voltage.
Relative to the older stuff, there's very little in them any more.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[scott nutter1]

I am also in the same predicament .
I just bought a Alpine Bluetooth indash receiver. Pulling out the old realistic unit I noticed a small round harness connector. 5 wire.
Is this standard for a 78?

If I have to run new wires to the small overhead speakers, should I just relocate newer larger speakers?
How much of a pain is it to run new wires to the original overhead speakers?
Where in the cockpit would be the best location for new speakers?
Or should I just run some type of Bluetooth sound bar and skip the wiring all together?

Last ditch option,
Use the rca preamp outputs from the stereo to a power amp, then run satellite speakers with a subwoofer!

Thanks, Scott
--
Scott Nutter
1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, tankless water heater.
Houston, Texas

 

[Matt Colie]

Scott,

Think about doing this. It means you have to pull 4 runs, but it was worth it.
http://www.gmcmhphotos.com/photos/speakers/p35249-where-i-put-new-speakers.html
It is about like have open headphones. Both of us get to hear stereo and the 4x6 are close enough to deliver bass.
The left side is the front and the right the rear, so the level can be customized easily.

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

 

[scott nutter1]

Matt,
I really like your setup. I could see how it would be similar to headphones!
I am just a little squeamish about cutting holes in the headliner cap.
Scott.
--
Scott Nutter
1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, tankless water heater.
Houston, Texas

 

[johnny]

Scott, a '78 originally had two wire speakers most of the time. Pop one of the front overheads and check to see if one side is grounded.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[thomas phipps]

Crutchfield sells a device to handle the floating ground. If you intend to use the OEM speakers, as I remember, they are 10 ohm. Most (all?) modern
car audio systems use 4 ohm speakers.
It is not hard to run two wires to each speaker. Remove the existing speaker assembly, run wires down the side of the headliner, grab the wires at the
rear of the headliner, remove the plastic on the toll windows, hide wire, run wire forward behind side wall plastic, slip into dash plastic, finally
attach to radio. Lots of wire, but easy to do.
I installed a set of marine speakers from West Marine to resist the water running inside the coach.
Tom, MS II
--
1975 GMC Avion
KA4CSG

 

[ree.eric]

Matt, I like it! I will run new wires. Headliner down again! Center overhead light at the same time perhaps. I will check the marker lights at the
same time, many are not working, read something here about ground problems.
--
Eric & Ree '74 ex-Sequoia (parts) '75 Eleganza (TB, exhaust x-over blocking plates, Manny reaction arms and discs, 3"exhaust rear muffler, aux vacuum,
fuel tank sealing, rebuilt senders and new rubber, propane hot water heater.) Alexandria, Ontario, Canada

 

[johnny]

Eric, if you're going to the trouble of taking the headliner down, run some spare wires whiile you're at it. One day you'll use them.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[scott nutter1]

Matt,
Out of Curiosity, on your setup, if I have front and rear speakers outputs on my stereo I could wire wire it to have true stereo over each cockpit
seat(I think).
Use the front channels for the left seat, and use the rear channels for the right seat. And use the fader control to adjust volume from left chair to
right chair.
It looks like you have the same speakers in all 4 locations?
Anything I'm missing?
Scott.
--
Scott Nutter
1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, tankless water heater.
Houston, Texas

 

[ree.eric]

Johnny, Now what would I use the extra wires for? In a Saab 9000 I still have in the back field I had a Radar detector mounted in the roof panel
wired with the roof light and if I turned off the roof light it would turn off. I got stopped coming from Vermont back into Quebec by 2 police
officers in a car who detected that I had Radar detector as they pass me in the other direction. I feigned not being able to understand french well
while they searched for the detector in the standard location in the front of the car. They went back to their car and while they were there I removed
the fuse that powered tho roof light ( the fuse panel in the Saab was located in the glove box) When the officer returned he sat in the driver's seat
looked at the dash and then the roof and tried the roof light, too late, no power, no beep. They had threatened to impound the car to better search
it but gave up and let me go. By the second time I got stopped by an unmarked police car in Ontario I had added a magnetic alarm switch in the roof
and I just had to pull the small magnet off of the roof to disable the detector. He also could not find it but actually he had to let me go as he
received a more important call.
Don't think I will be using a Radar detector in the GMC and I do drive at the speed limit nowadays ( + 20% of what is posted here in Ontario).
--
Eric & Ree '74 ex-Sequoia (parts) '75 Eleganza (TB, exhaust x-over blocking plates, Manny reaction arms and discs, 3"exhaust rear muffler, aux vacuum,
fuel tank sealing, rebuilt senders and new rubber, propane hot water heater.) Alexandria, Ontario, Canada

 

[Matt Colie]

> Matt,
> Out of Curiosity, on your setup, if I have front and rear speakers outputs on my stereo I could wire wire it to have true stereo over each cockpit
> seat(I think).
> Use the front channels for the left seat, and use the rear channels for the right seat. And use the fader control to adjust volume from left chair
> to right chair.
> It looks like you have the same speakers in all 4 locations?
> Anything I'm missing?
> Scott.

Scott,

That is exactly what I do, and better than that is that the remote is velcroed to the overhead by the passenger so he can either push the fader or
decrease the system volume. It works great.
(Another secret... With the new fan, most of the time things are quiet enough that we can turn the music down and still hear it.)
The light in the middle works better too.

The problem came when I put in the new and working radio, I replaced the existing speakers with the best 4x6 I could find. After a very short trial,
I realized that even with my bad hearing, I was only hearing half the program. I set about to fix that.

To fish wires over the headliner, get string and two magnets. Put one magnet in a small square of nylon or other slippery cloth and tie the string
on. Use the other magnet to pull it along.

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

 

[johnny]

Like the song says, "Who knows what tomorrow will bring..." Back up camera, rear A/C evaporator,power for a Brake Buddy, who knows? We always double
wired new studios, they were used up on average in ten years. It's your frustration, but wire is cheap and opening up the topis a PIA. I wouldn't do
it nore than once for the price opf a hundred feet of 18 ga.

And, while Ga doesn't try to detect detectors, most of the design guys at Scientific Atlanta never got stopped for speeding. One of them told me alls
you have to do is pick the signal off the detector and transmit something downshifted about 80% - or whatever offset you wanted including variable -
and take advantage of the receiver's capture ratio. Now they're all using lidar, maybe swamp it with a diode?


--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased