Just now, SteveJ said:

Does the stereo manual specify 4 or 8 ohm speakers?

The head units manual?

Yes

7 minutes ago, SteveJ said:

Yes

Honestly I'm not sure since the head unit came with the car.  I'll grab the model number off the unit tonight and see if I can find the manual.

19 hours ago, chaseincats said:

bolted directly to the metal of the car so I insulated one with a rubber grommet between the speaker metal and bolt

This does not matter.. the speaker's housing is totally isolated from the speaker's coil.  Most radio's (amp's) are NOT happy when you use the minus or chassis on one side of the speaker..  You need to use 2 isolated wires from the amplifier to the speaker, NO ground! (Do not ground one of these wires onto your cars chassis!) 

19 hours ago, chaseincats said:

So you're telling me that my testlight lighting up when I touched the power wire to the speaker with music playing is bad and can blow speakers even at a low volume?

Eh... No.. But it can blow-up your amplifier!  When you put a testlight (basicly a resistor of low impedance..) between a 12V+ and a speakerwire.. you are putting a voltage (DC) on a amplifier output and that can be catastrophic! 

(Personally i NEVER use a testlight always a multimeter or scope.)

If you put some DC on a speaker, do this with a 10-20 watt old speaker and a 1,5 volt battery.. when you put the 1,5v to the speaker you will see the cone go in or out depending on where you put the plus and minus!

So you can imagine the music signal must be AC as the cone moves on the music IN and OUT..

Imagine.. that speaker cone gets a signal made out of many,many!! frequencies and it has to "speak out" ALL of these frequencies at once!!  Now you probably have much more respect for a speaker..  

About home audio...

As an audiofile (My other expensive hobby 😉 )  I got some experience with amps and speakers..  The speakers are the most important part in a audio system.. you can have a perfect set of Amps/recorders/players/tuners but when your speakers stink.. you'll have no good sound.

I don't expect a good sound out of a speaker that cost 30$.. Personally i listen to speakers more in the range of 1000-3000$ (Studer's ReVox Symbol MK2's and Zachry EM24's (These are from the 70's and 80's!))

Here some dream speakers....

 

Edited March 22, 20232 yr by dutchzcarguy

6 hours ago, dutchzcarguy said:

This does not matter.. the speaker's housing is totally isolated from the speaker's coil.  Most radio's (amp's) are NOT happy when you use the minus or chassis on one side of the speaker..  You need to use 2 isolated wires from the amplifier to the speaker, NO ground! (Do not ground one of these wires onto your cars chassis!) 

Not sure where the black wire is goes to in these cars but its from the stock harness

6 hours ago, dutchzcarguy said:

Eh... No.. But it can blow-up your amplifier!  When you put a testlight (basicly a resistor of low impedance..) between a 12V+ and a speakerwire.. you are putting a voltage (DC) on a amplifier output and that can be catastrophic! 

As far as I know there isn't a separate amp since these go through the stock harness to the radio

From what I remember when putting the stock radio back into my '72 the ground was through the chassis.

The black wire is from the antenna.

Did you alter the factory harness what so ever when you installed the radio. That will give us a heads up on the installation.

1 hour ago, Yarb said:

Did you alter the factory harness what so ever when you installed the radio. That will give us a heads up on the installation.

If I did, I don't recall doing it.  The car did come with a big stupid sound system/amp which I promptly removed.  It's possible the PO did something to get that thing to work but I believe I removed all of it.

9 hours ago, chaseincats said:

Not sure where the black wire is goes to in these cars but its from the stock harness

As far as I know there isn't a separate amp since these go through the stock harness to the radio

So the car has an aftermarket stereo, correct?

Given that, and that these cars didn't come with much in the way of hi fidelity audio systems back then, the OEM wiring shouldn't be relied upon to get the audio signals to the speakers. 

And the speakers. Rockford Fosgate speakers are typically good, better quality speakers. Rather than rely on the less than adequate OEM wiring, you should have dedicated, proper gauge wires running from the stereo to the speakers.

Also pay close attention to polarity, and keep the phasing the same right to left. This is more of a sound quality thing than a longevity issue, but still important.

Impedance is also important, the speakers need to match the impedance of the stereo output. If the stereo has 8 ohm output, then the speakers should be rated for 8 ohms, if it has 4 ohm output, the speakers should be 4 ohm.

 

Edited March 23, 20232 yr by Racer X

I used a square 9 volt battery to get the pluses and minuses right when I cared about loud. Now I use my phone and a bluetooth speaker when, hardly never!, I go long. The exhaust is Rod Stewart sounding.

I've always thought 12 volt car stuff was the lower 4 ohms because of the lower power 12 volt systems have. 110/120 house volts is 8 ohms.

Is it 110-220 or 120-240 AC volts? I've heard both over my life but would like to know. 

19 hours ago, chaseincats said:

As far as I know there isn't a separate amp since these go through the stock harness to the radio

I was talking about the amp that is (always one) IN the radio..  For as far i know has the original radio a double wire for the (mono) speaker and is not attached to the chassis of the car. With a Ohm-meter you can always check if there is a connection between the speakerwires and ground. there should be none! (disconnect the radio when measuring the wires.) 

Speakers can be 4 or 8 ohms that's not very important.. You can mix them when you attach a 8 ohm speaker to a 4 ohm amp output you will get only half of the power out but still enough.. when you put a 4 ohm speaker to a 8 ohm output you will hear that it starts to scream/distort at you.. sort of..  as the volume go's up you'll have to watch the temperature of your amp. but most times it's no problem.. The problem starts when you constantly listen music on max power then your amp could get to hot!  (Another solution is to series 2 x 4 ohms speakers to get 8 ohms, then you'll never can blow up the amp and the speakers can handle twice as much power!) 

 

10 hours ago, siteunseen said:

Is it 110-220 or 120-240 AC volts? I've heard both over my life but would like to know.

You guys in america have 120v and 3 fase 220 volt That's what i thought..

But you make a mess of it!!  I looked it up and see that the united states have: 120/208 V / 277/480 V / 120/240 V / 240 V / 480 V  (all at 60 Hz) !

Her you go Cliff! : Complete list: Three-phase electric power (voltages/frequencies) - World Standards

I think most North american states have 120/208 volt ( so one line  (1 phase against ground*) is 120volts and 3 phase is 240volt between the phases.)

We've gone from 220v/380v to 230v/400volt about 15 years ago..

* I don't know how you call the 0volt wire.. so i called it ground..

 

2 hours ago, dutchzcarguy said:

I was talking about the amp that is (always one) IN the radio..  For as far i know has the original radio a double wire for the (mono) speaker and is not attached to the chassis of the car. With a Ohm-meter you can always check if there is a connection between the speakerwires and ground. there should be none! (disconnect the radio when measuring the wires.) 

Speakers can be 4 or 8 ohms that's not very important.. You can mix them when you attach a 8 ohm speaker to a 4 ohm amp output you will get only half of the power out but still enough.. when you put a 4 ohm speaker to a 8 ohm output you will hear that it starts to scream/distort at you.. sort of..  as the volume go's up you'll have to watch the temperature of your amp. but most times it's no problem.. The problem starts when you constantly listen music on max power then your amp could get to hot!  (Another solution is to series 2 x 4 ohms speakers to get 8 ohms, then you'll never can blow up the amp and the speakers can handle twice as much power!) 

 

You guys in america have 120v and 3 fase 220 volt That's what i thought..

But you make a mess of it!!  I looked it up and see that the united states have: 120/208 V / 277/480 V / 120/240 V / 240 V / 480 V  (all at 60 Hz) !

Her you go Cliff! : Complete list: Three-phase electric power (voltages/frequencies) - World Standards

I think most North american states have 120/208 volt ( so one line  (1 phase against ground*) is 120volts and 3 phase is 240volt between the phases.)

We've gone from 220v/380v to 230v/400volt about 15 years ago..

* I don't know how you call the 0volt wire.. so i called it ground..

 

Since you're going down that path...

Most non-industrial facilities in the US are bringing in 208VAC (two phases off a WYE transformer). At the entry point for the facility (service entrance), there is a neutral (return path) bonded to ground. That is put in the circuit with one of the legs of the 208VAC to provide 120VAC.

In Canada, instead of using 480VAC as low voltage, they use 600VAC.

The fun part is to source parts in North America for equipment to ship to a 50Hz country since almost everybody in North America publishes specifications for 60Hz.

The most fun was a project where all of the equipment downstream operated at 60Hz. The generators operated at 60Hz, and it was being installed in Europe. They had to place equipment in between the utility and our equipment to go from 50 to  60Hz. Ships have to deal with this, too. For instance, the US Navy ships are designed to support voltage and frequency used in America. When they get shore power while docked in foreign ports, they have to have the frequency converters between the shore and ship.

Going back to @chaseincats (to pretend that this rambling is still a little on topic), as @Racer X explicitly said, match impedance between the stereo and speakers. Mismatched impedance will work, but not as well.