so i got a bunch of store display model speakers cheap. alpine 4x6 plate, and 3 way pioneer 6x9s. i took the coupler off the old speaker and soldered it onto the new speaker so i wouldnt have to hack up the cars wiring harness, and it makes it easy to remove.

now heres the dumb part.
my cars wiring harness is one brown wire with a grey stripe, and one grey wire.

i have no idea which is neg or positive.

 

Doesn't matter.

 

Wrong- speakers must be kept in phase or you will get phase cancellation when in the center. Meaning + and - on the speakers must coincide with the positive and the ground at the radio. Usually all the speaker grounds will be common or tied to each other internally in the radio. You can measure with an ohmmeter with the radio off the bundle going to the speakers, all the grounds should measure 0 ohms, the other wires will all be the speaker + side.

 

Another question what's phase cancellation?

 

Phase cancellation is a null in the audio that occurs if the speakers are wired opposite each other, that is if you wire one side opposite polarity from the other. It can be best heard when listening in the center of the 2 speakers. Thats why amps and speakers are always marked + and - to maintain correct phasing.

 

look at the pic below...

imagine the right top wavy line is the sound from speaker 1

the bottom wavey line is the sound from speaker 2.


if you're directly between the speakers, so the noise from each arrives at the same time, the two add up together and look like the line below.... they cancel each other out.





if you want to think about it in "real life" terms, imagine the speaker cone on one side going in to the left, while the speaker cone on the right goes out to the left... if they move together like that, the air just moves back and forth, and they cancel each other out.

 

Go buy a digital multimeter at radio shack for 19.99 and learn how to use it on the voltage setting.

Connect one lead to one wire and the other lead to the other wire.

Red is positive, black is negative. Oh and do this with the stereo ON.

If the meter reads a negative number (let's say - 0.22 volts) then that means the wire that the RED lead is touching is the NEGATIVE wire. In other words, if you get a negative number, your leads are opposite of the wire. If you get a positive, then the red lead is in fact touching the positive wire.

 

while that works for most DC circuits, that wont work for a speaker.

 

It won't work on the speaker itself no. It works on the speaker wires that are in your car. Try it yourself, I did this on my blazer just last weekend.

 

well im going to try that trick with the digital multimeter this week.
seems i got the audio bug and upgraded the front alpine plate speakers to an infinity set. only had them alpines in for 4 days too. havent put the dash back together yet [trying to track down a noisy air leak] so it wont be a chore.

 

that is nice to know, and knowing is half the battle

 

go joe