Powered subwoofer wiring question

[G50]

Maybe I’m not understanding electrical principles here.

But wiring a powered subwoofer, it says to use 8 gauge wiring for the power and the ground.

Seems fine. But then the wiring harness coming out of the amp is maybe 16 gauge.

Doesn’t that basically negate the 8 gauge wiring 12v and ground?

I get it if the 12v and ground wires are 50 feet long. But this is in a small car. I’d use maybe 3 feet of 12v wire, and I could ground the amp directly from its wiring harness to the chassis. Calling for massive 8 gauge wire to connect to a 16 gauge harness doesn’t make sense to me.

Am i missing something?

[G50]

[908/930]

The larger gauge helps eliminate voltage drop, so if pretty close to battery can use smaller. Make sure you place a fuse right at the battery.

[RANDY P]

You'll never need 8GA but in this scenario (nor will that amp ever need it, ever- just a marketing gimmick to imply 'big power' )

Run 8GA with a good fuse from the battery- if you're gonna go thru the effort use the larger wire, you'll only need to run it once in case you upgrade later.

From there, put it into a distribution block

then go to whatever wire that amp uses.

Don't forget a good ground.

Done

[G50]

Got it done, thanks.
When I stripped the wires, I found that the sub wire was thicker than I thought, and the 8 gauge thinner. The 8 just had much thicker insulation. Actual wire size wasn’t too far apart.
Sounds pretty good, in a small car I can’t imagine wanting more bass than that thing can put out!

[Rusty Heap]

Any Questions?

[rwest]

Originally Posted by Rusty Heap

Any Questions?

So many, but can’t remember them right now...

[G50]

Ohm my!

Ok, another question. My radio is an 80s, with a Bluetooth amp put into it. So I’m not using any of the old radio electronics.

It now has 2 high powered speaker outputs (L and R) coming out of it. Each of those is split using the pictured splitters, so it’s 4 speakers.

With that setup there’s no fader control.

Could I wire my stock fader knob into it? As shown in the wiring diagram, the fader uses some kind of “common wire” system. Possible?

[G50]

I was thinking I could just wire it per the diagram, but I’ve read about these 80s systems having “common ground” speaker systems, which aren’t compatible with modern equipment (which is why these faders aren’t usually used).

In the diagram the left side speakers do share a ground, as does the right. Does it matter?

[908/930]

That should work. Are you using stock speakers? Do the negative wires from the speakers terminate at the back at the radio?

[G50]

I’m using 4 modern 4x6 speakers.

The 8 speaker wires terminate into 2 of these. Which goes into the L and R channels on the BT unit in my radio.

But I think you’re asking if the speaker wires are grounded to the chassis? They are not.

[G50]

[908/930]

Yes I was asking if your car was using common ground, the wire diagram did not indicate this. Probably was something like the Chrysler K car that used that to save $1 in wire.

Is there any built in resistance in those speaker terminals? One thing you should check is the impedance of your speakers, usually 4 ohm for modern auto, but when joining them in parallel like those adaptors do the result will be 2 ohm. Your amplifier needs to be rated for that, or can run hot and eventually let the magic smoke out. There is a good chance that that factory fader has some internal resistance built in.