Easiest Way To Verify Stereo Amplifier's Speaker Polarity?

I was studying the wiring diagram of my car's speaker system and noticed a discrepancy in the wiring's color coding of the left side speakers. The wiring goes through several wiring harness connectors and changes colors in the process. The left channel of the wiring diagram color codes don't match reality. While attempting to electrically trace the wiring I realized that it's possible that the harness on the rear of the head unit may also be incorrect.

Without removing the head unit, assuming it's polarity is correct (there are no +/- markings), is there a reasonably easy way to verify speaker audio polarity?

 

Not sure if it applies to car audio, but many of the amps I've owned have the negative speaker lead tied to chassis ground. It's worth checking on the amp.

 

Are you worried that your speakers are out of phase or reversed polarity?
For both there are test records/cds but reversed polarity may be difficult if not impossible to detect in the less than ideal situation of a car. Out of phase is easy. There are many ways and Steve our host has an excellent method if you do a search for "out of phase" I would presume, but basically if centre vocals sound vague and hard to identify in the space it may be out of phase. reverse a wire to a speaker and test again.

Polarity (and phase for that matter) is also easier I found on subwoofers. Play some bass heavy music and listen, then reverse the leads and listen again. You will know when the polarity is right for you when you hear it.

In my experience it's also not out of the ordinary for car wiring colours to change as it moves through harnesses. I cannot tell you how frustrating wiring my Volvo was to my inexperienced mind. In the end I just had to trust and test.

Hope this helps

 

If it is absolute polarity you want to test, do you have an oscilloscope? If so, you will need a sawtooth waveform (|/|/| or |\|\|), and then measure on the speaker terminals with the scope. If the trace matches the sawtooth you inject, the polarity is correct. If you do not know which terminal is + or -, you will need a microphone to probe the output of the speaker.

 

Can you see the action of the speaker cone (assuming a woofer is in the circuit)? If so, a simple AA battery is all you need. Connect what you think is positive to the button top of the battery, then connect the other lead to the negative side and if the woofer pulses out, you have your wires identified correctly. If it pulls inward, you are out of phase.

If you can't see it? What they said^

 

There is an android app called absolute polarity that does just that. Plug it into your head unit and look at the screen. Works great on home stereos. Free as well.

 

Like this?

 

I used the Speaker Pop app on my iPhone and discovered my subwoofer is out of phase "-" relative to all the other speakers "+". I just sensed there was something amiss.

Nice and easy to use app, BTW.

Thank you all for your suggestions.

 

I could not find this. Can you please send a link?

 

Oops, the app is called Polarity Checker and it is in Google Play under the apps section. Just enter Polarity Checker in the search box. I have no way of sending you a link.

 

Turn your amp up all the way and place both leads from your speaker wire in your mouth.."....

You will definitely know when you are in phase......

Seriously, stereo speakers wired out of phase will have much less bass response than those in phase. Not too hard to hear if you relax and listen....

 

Kind of what I was thinking. I always know when I wired reverse polarity by the bass response. If it is diffuse and boomy, I got it backwards. Tight and focused, I'm good.

 

Thanks, found it

 

Kind of hard using only your cochlea to determine which speaker(s) are out of phase when there are nine of them

 

Use a 9volt battery. When the you connect the battery to the wire leading to the speaker, and the cone pushes outward, it's wired correctly. If it falls back, it's not.

So, not only do you want all speakers to be in phase with each other, but you need to make sure the positive signal hits the correct terminal on the speaker. Note that speakers are sometimes built incorrectly with respect to the labeling, or vice versa

That is all

 

The Speaker Pop app is even easier

 

^^The other thing regarding the battery test is that only tests from the wire to the speaker itself. What about all the intermediate steps? For instance I just bought a new pre-amp that when tested reverses polarity. Without being able to inject a signal into the unit I would have had no way of knowing that I needed to reverse the speaker wires. It's free so even cheaper than a 9V battery

 

you WANT your subwoofer out of phase with the main speakers in a mobile audio application.

 

Just testing the woofer for phase does not guarantee that a speaker is in phase. Sometimes drivers are intentionally misaligned by the manufacturer when voiced. You need to look at an impulse graph to see what is really going on with a loudspeaker.

Take these from a recent Stereophile review. In these the tweeter is out of phase. It doesn't make it wrong and changing it will change the voice of the speaker. What if the speakers you are testing were designed with the woofer out of phase from the mids and tweets?

 

Interesting, I didn't know this until I dug into this project. I would rather not dig into the sub to change the original "-" phase as it is difficult to get to.

However, my curiosity wants to know, why should the sub be reversed?

 

Because of competing pressure pulses within an enclosed volume. Ever see your rear view mirror or large area of window glass start deflecting when the subwoofer pulses?
That same pressure is actually working against your other speakers if they are in phase. In other words, your door midwoofers have to fight against the pressure pulses from the subwoofer during their own pulses. They struggle, and the result is less midbass. If you reverse the phase / polarity of the subwoofer, the door woofers are no longer fighting against the subwoofer pressure. In fact the subwoofer reverse pulse actually creates less pressure and the midwoofers breathe easier.
Bottom line- you get more midbass and sub-bass when the sub is reverse polarity. I notice this quite easily in my car- at the flip of a switch I adjust the subwoofer phase. This actually applies to home subwoofers as well.
Does your head unit have a subwoofer phase control?

 

No, it doesn't. But I left it in same reverse phase as the original factory sub when I replaced the factory sub driver (same size).

Apparently the phase of the "tuned" factory HU's sub output is already reversed since the wiring color codes indicate "+" as being "+".

Your explanation makes sense. I just assumed, wrongly, that in phase was always correct.