Crazy, old audio wiring

[mylo]

So, I took the old, original cassette, AM/FM deck out of my rig today. I just couldn't handle the old analog radio tuning, no presets or aux input, etc.

I was shocked (no pun intended) to see only 6 wires going into the old head unit. Four +'s for each of the four speakers, and a red and black for power. I did see some soldered connections with shrink tubing. I didn't, however, see the wiring harness plug that corresponds to the one I bought downstream from that. I assume the only way this works is that each speaker's negative must be directly tied to chassis ground? The new radio's harness has discreet negative conductors for each of the four. I guess I will just ignore these? I can't really rip everything up, searching for the truth...

I look forward to the iPod, Pandora, and Bluetooth capabilities of the the new head unit. I intend on hooking up the constant and switched leads to the house side of the isolator, so I can run it while boondocking.

Can someone corroborate my theory? Thanks.


Mylo

 

[SeilerBird]

Sounds to me like one negative lead for each speaker is the way it was wired. However the unit you replace it with may not work that way. Many modern units float the ground and if you tie the speakers into it then the speakers won't work. I would suggest replacing the speakers and the speaker wire also. A new stereo ran through old speakers is not going to sound all that great compared to a new stereo with new speakers.

 

[Alfa38User]

One way to check the speaker wiring would be to use a 1.5V "D" size (flashlight) battery. Ground the negative side to the frame and touch a speaker wire to the positive button. If you hear  a sound from the speaker, it has been grounded directly from the speaker to somewhere, likely nearby to it.

But as SeilerBird said, new systems don't use grounded speakers and that arrangement is likely problematic. The newer ones are 4 ohms, the older variety were 8 ohms.

 

[John From Detroit]

Speakers to chassis ground was at one time very common.

Some of the modern radios can deal with it, Some can not, all depends on who made 'em.  I can't tell you which are which however.  Sorry.

 

[mylo]

Well, might have gotten a little stroke of luck. On closer inspection I see four more wires I didn't see yesterday. They are all twisted together, and tied to ground. So I think that I have two wires to each speaker all the way back to the radio compartment, and can wire it properly. I didn't have my multi tester with me to confirm, but I will this weekend. Big sigh of relief. I didn't want to rip up the whole rig trying re run all four speaker wires.

Thanks for all the advise, gentlemen.


Mylo