Rustbucket2

I have a 70 cutlass, it has the one speaker in rear, with one blue wire ,so speaker must ground on body ? can I put a splitter in and run two rear speakers, but ground both to the body?

RandyS

Yes, and Yes.

oldcutlass

x2 on the yes's

Rustbucket2

That's great, thanks for the input, I hoped it would be that easy.

al1950

yes to both, assuming you have a mono radio.

Rustbucket2

Ok, I will admit, I don't know what a mono radio is! My car has a AM/FM stereo with 8 track player,and multiplex , the car did come with just the front speaker and one rear speaker ( with one blue wire hook up). Is this still a easy wire job?

Yellowstatue

With the radio on stereo, the front speaker is the left channel and the rear speaker is the right channel. If you add another speaker to the rear you will have two outputs of the right channel.

al1950

Does your rear speaker sound good and have similar sound output as front when you adjust from front to back?

Rustbucket2

Have not hooked the rears up yet, was making sure I can , with one wire. Front speaker works great, but was a new replacements unit.

oldcutlass

Another assumption on my part. I thought you had a mono (single channel amplifier) radio. As stated above you have a stereo (2 channel amplifier) radio and it may not sound right with 2 speakers for 1 channel vs 1 speaker for the other. I would leave it alone.

al1950

X2 on that, if it sounds good with one rear, adding another will not make much difference. if the rear s a good speaker you should be good to go.

jaunty75

Wouldn't there also be an unbalanced load on the amplifier? If each speaker in his current setup (one front speaker, one rear speaker) is rated at, say, 10 ohms, and he replaces the rear speaker with TWO 10-ohm speakers, he effectively has two 10-ohm resistors wired in parallel. As we all remember from high school physics, two 10-ohm resistors in parallel is equivalent to a single 5-ohm resistor. The formula for the effective resistance for two resistors in parallel is 1/R = 1/R1 + 1/R2. Substitute 10 for each of R1 and R2 and solve for R.

So his amplifier would be effectively seeing one 10-ohm speaker and one 5-ohm speaker. Is that good for the amplifier? I wouldn't think so. Would the volume level of the two rear speakers be half what a single speaker would be, or would each be just as loud as if there were a single speaker, and would THAT be good for the amp?

Going a little further, and I'm not at all sure I have the thought process correct here, an amp's output is rated in Watts. I don't know what the power output of an Olds radio is, but an aftermarket radio might be, say, 25 Watts per channel. P = I^2 x R, or I = square root of P/R. For the front speaker, P/R is 25/10 = 2.5. Square root of that is 1.58. For the rear speakers, P/R = 25/5 = 5, and the square root of 5 is 2.24. So the front speaker will pull 1.58 amps from the amplifier while the rear speakers will pull 2.24 amps, or just over 50% more. Again, will this harm the amp?


If the above is actually correct, he could avoid the problem by using two rear speakers rated at 20 ohms each. In parallel, they'd have an effective resistance of 10 ohms. 20-ohm speakers are probably not available. But 4 and 8 ohm speakers are. He could replace his front speaker with a 4-ohm speaker and use two 8-ohm speakers in the rear. But I don't know if a vintage Olds radio would be harmed by using such low-resistance speakers. Of course, the OP hasn't said what radio he actually has, original or something aftermarket.

Rustbucket2

It is factory set up. This is why I like this forum, I was so fixed on two speakers, because they came in a pair out of box, never even dawned on me to use one!! How stupid is that. I will mount both, but only hook up the one. ( in case someone else would want to hook up both ) Thanks. boy do I feel stupid