Speaker wiring questions

[kevin316i]

I got my hands on an old Pioneer radio casette, just like the one in my previous E30, and was delighted till I checked the wiring and found it is only able to take two speakers. It's a Pioneer KE 3090.

The units states '4~8 ohm' on the back, so I guess I could wire the front and back speakers in series on each side, which would give 8 ohms from the two 4ohm speakers.

I'm wondering if it will decrease audio output much? Despite only having wiring for two speakers, it states '8.5w x 2 or 7w x 4' on the cassette slot door and reference 'fader control' on the door also. There is no fader, and as far as I can see, there are no speaker wires missing from the back of the unit.

For units with output for four speakers, is each side split in series internally in the unit? Do you think I will get the 7w output per speaker if I go ahead and wire my speakers in series?

Another solution would be to get 8 ohm speakers and wire in parallel, but all car audio speakers seem to be 4ohm. I'm not looking for a high output system, but one that is in keeping with what was originally fitted. I can bring it back to scrappers, but its very difficult to find original units like this.

[kevin316i]

Think I misinterpreted the wiring, from a wiring diagram I found on the net, looks like all the +ve wires are present for four speakers, but no -ve wires. The diagram shows the -ve speaker wires ending at the common grounding point on the stereo? Does this make sense?

[placey]

sounds to me like a case of some trial wirings and see what sounds best. id your motor especially original?

paul

[Brianmoooore]

Think I misinterpreted the wiring, from a wiring diagram I found on the net, looks like all the +ve wires are present for four speakers, but no -ve wires. The diagram shows the -ve speaker wires ending at the common grounding point on the stereo? Does this make sense?

Common -ve sounds right.

[kevin316i]

Thanks, the reason I was unsure is that modern units with ISO connectors have indivdiual connections for both +ve and -ve speaker wires going into the back of the unit. However, this old Pioneer unit doesn't. Guess I'll make up some connector wires for each of the -ve speaker cables and connect them to the ground point on the back of the unit.

[miniblob]

You could always get a small 4 channel amp which will take low level speaker inputs and hide that away somewhere.

It will give you a much better sound!!

[kevin316i]

I'm tempted, but want to have an original as possible installation. Just wondering about the grounding of the negative speaker connections, is it important where they are grounded?

[Globulator]

Have you got the original BMW fader in there?
Take out the boot-trim or feel behind the bulge and see if you have the amp fitted.

The speakers are +ve drive only, chassis ground via the fader. Power is low, do a complete rewire if you want both wires to each speaker.

Two speakers in series gives 1/2 the voltage to each speaker, for one speaker Power = V.V / R (roughly)

Two in series therefore get 2.v.v/R where v = V/2 so the power ratio is
V.V / 2.v.v = V.V/2.V.V/4 = 1/8 total power.

So they will be quiet.

I rewired mine, it's really the only way.

P.S. grounding any wire of a modern high output radio will kill it or blow the fuse. Both wires need to 'move'.