98 Bonneville....rear speaker wire polarity

[Rolandgp16]

Getting ready to change out some stock speakers (6 by 9) in the rear and want to make sure I hook up the new speakers with the correct polarity. Appears to me after I mark and cut the wires (will have to do so to hook up new speakers) that I could use an ohm meter and touch one side to metal of car and the other to each speaker terminal to find the ground. Any thoughts?....

[00Beast]

Lots of times they're marked on the speaker, otherwise someone here should have access to a wiring schematic for them.

[Rolandgp16]

Actually I would need to touch metal on the car and then touch each speaker wire that I cut to isolate the ground

[00Beast]

Someone here has the schematic, or it might already be posted, or the speaker might have a + and - on it when you remove it. If you use a multi-meter, have your stereo on and touch a wire to the red end and touch the black end to a piece of metal on the car, the one that shows voltage is the positive, and if it doesn't it's the ground. Usually the speakers have a short pigtail on them that goes from the connector to the poles on the speaker; it's going to be in your best interest to keep that connector intact, if you ever need to remove the speaker from the car.

[MattStrike]

Getting ready to change out some stock speakers (6 by 9) in the rear and want to make sure I hook up the new speakers with the correct polarity. Appears to me after I mark and cut the wires (will have to do so to hook up new speakers) that I could use an ohm meter and touch one side to metal of car and the other to each speaker terminal to find the ground. Any thoughts?....

Dark is '-' and light is '+'

Your method to test won't work, because the ouptut from the stereo is on a 6v plane. Meaning, to the amplifier car 12v = stereo 6v+, car 6v = stereo gnd, car gnd = stereo -6v. Because it has to generate alternating current to drive the speakers.

So when you measure, both wires will show 6v.

[andrewsowinski21]

yes the darker color is always negitive and lighter colors positive is also the same for bose and monsoon

[Bugsi]

Your method to test won't work, because the ouptut from the stereo is on a 6v plane. Meaning, to the amplifier car 12v = stereo 6v+, car 6v = stereo gnd, car gnd = stereo -6v. Because it has to generate alternating current to drive the speakers. So when you measure, both wires will show 6v.

Well no, they won't. [Edit: Actually yes, they will.] The speaker wires do not carry a +6 volt DC bias voltage. [Edit: Actually yes, they do.] The amp circuit in the radio would, but the signal will pass through a capacitor in the radio (and external amp if equipped) before the speaker terminals or wires that go to the speakers. [Edit: The speakers are never referenced to the vehicle ground, so there is no DC current flowing through the speakers as a result of their ground being 6v DC higher than the vehicle chassis ground.]

Audio is AC. If you sent a DC bias voltage to the speaker, the speaker would surge forward and stay there until the current in the speaker's voice coil burned it out to an open circuit. [Edit: True, if such a voltage is referenced to the speaker's ground, which is independent of the vehicle chassis ground.]

If you measure the speaker terminals with a voltmeter they will read ZERO volts DC, not +6. [Edit: Actually if you measure DC voltage between either speaker terminal and vehicle chassis ground with the radio on, it will measure +6v DC.]

The important thing to answer here is that neither of the speaker terminals are tied to the car's DC ground, [Edit: True] and the proposed method to determine + from - will not work. [Edit: Also true] Go with the color guidelines others have already posted. [Edit: Still good advice.]

[Mad Myche]

GM stereos run on a floating ground, so as stated previously you are not going to find out by measuring resistance from wires to ground

Also, as previously stated, audio is AC; and as such, there is no positive and negative. The terminal markings are mere references for keeping the speakers in phase with one another. Hooking both up the same way is the goal. The only thing that will happen if you reverse one is lower volume, as long as its at the speaker connection.

[MattStrike]

Audio is AC.

it has to generate alternating current to drive the speakers.

AC is alternating current.

Well no, they won't. The speaker wires do not carry a +6 volt DC bias voltage.

Yes, they do. My DMM says they do. They have to. Because these ('95+) GM radios don't have a power supply to generate a -12v potential to GND, and even your basic OP-Amp requires positive and negative DC voltage power supply (+, GND, -). The amplifier whose bias voltage (GND) is +6v dictates that the potential measured at any speaker terminal is a 6v potential to vehicle ground. Remember, the speaker coil (who rides on the +6v DC plane) is not attached to the vehicle ground anywhere, so there is never DC potential being delivered to the speaker. The amplifier at it's most basic function switches one of the speaker wires between the + and - supply to generate an A/C signal with respect to the amplifier GND, the other speaker wire (6v DC potential to vehicle GND). When both wires are at amplifier GND, there is zero DC potential through the speaker. This switching voltage is very similar to the way the spark is generated in the ignition coils, which are simply transformers (transformers only work with AC). But that's a different topic.

GM stereos run on a floating ground

You make it sound so simple


When you hook a speaker up backwards to another in a perfect world they actually cancel each other out (being exactly out of phase with each other) and you'd hear nothing. But no two speakers can produce the exact same reproduction of the audio signal from the amp, and the distance between them also effects the cancellation efficiency. They seem quieter but the speakers are still individually producing the same amount of sound, they are just cancelling out (like one of those redneck truck tug-o-wars).

[Mad Myche]

When you hook a speaker up backwards to another in a perfect world they actually cancel each other out (being exactly out of phase with each other) and you'd hear nothing. But no two speakers can produce the exact same reproduction of the audio signal from the amp, and the distance between them also effects the cancellation efficiency. They seem quieter but the speakers are still individually producing the same amount of sound, they are just cancelling out (like one of those redneck truck tug-o-wars).

aka destructive interference

[Bugsi]

Yes, they do. My DMM says they do. They have to. <SNIP> The amplifier whose bias voltage (GND) is +6v dictates that the potential measured at any speaker terminal is a 6v potential to vehicle ground. Remember, the speaker coil (who rides on the +6v DC plane) is not attached to the vehicle ground anywhere, so there is never DC potential being delivered to the speaker.

Actually you're completely correct. Honestly, as I think about this I don't know where my brain was. Everything you wrote in your first post was spot-on. I think I was mixing up my reply to the OP's post with a reply to your post and now none of what I wrote makes sense. I'm going to add a couple edits to my post.

The amplifier at it's most basic function switches one of the speaker wires between the + and - supply to generate an A/C signal with respect to the amplifier GND, the other speaker wire (6v DC potential to vehicle GND).

Your description of how an amplifier works, however, makes me cringe to read.

[Bugsi]

If you have a speaker and don't know which of the two connectors is + and which is -, there is a simple way of determining which is which. Momentarily apply a small DC voltage (a 1.5v battery will do nicely) across the two terminals. The speaker cone will react by slightly moving forward or backward. If it moves forward, the + speaker terminal is connected to the battery + terminal. If it moves backward, the + speaker terminal is connected to the battery - terminal.