How to test speaker polarity?

Whether it's the best idea or not, the trick I read in a really old Radio Shack (so consider the source) book on speakers was to hook up a very small battery, something no bigger than AA size, to the wires of the speaker and note the direction in which the cone travels. If it moves out, the polarity is correct. If it moves in, it is reversed. You can then mark the leads accordingly. The book also cautioned to do this VERY briefly, not for any extended period of time at all. Basically, just a fraction of a second to see what direction the cone moves. Any longer than that can supposedly damage the speaker.

Again, it was a Radio Shack suggestion, but in theory it seems valid. I'm sure others will chime in about it, although if someone does have an argument against it I'd like to hear an actual bit of evidence as to why as proof. Something like a comparison of voltages, amperages, and duration against what a normal amplifier produces, etc. It's not like the things are made out of butterfly wings and are so delicate that a quick spike of that sort would kill them. Still, solid evidence in one direction or the other would help resolve my perpetual query as to whether or not it really is a truly bad idea or it it's actually a pretty good one.

You are correct that there will be a cancelling effect of sorts, although I've never noticed it personally.

Check to see if the speakers are labeled for polarity, and then tune to an FM frequency with just steady static, at a nominally loud level, and check with an analog voltmeter(set to under 10 volts scale) to see that each speaker is receiving the same polarity. The terminal brackets, and the cones/coil wires, should both be marked in some fashion as to polarity.

Ideally, it would be grand if the speaker expresses (pushes out) with higher positive input levels, but this can be very hard to discern.

On a sort of related note, good friend of mine from high school frequently drove his father's 1976 Grand Marquis... a real boat for sure... and fairly anemic at that weight with a smog-era 400M V-8 2bbl. His father insisted the factory stereo was wired backwards by F-L-M, as the strings were on the "wrong side" in the orchestral numbers he was tuning in to. I couldn't convince them that the perceived switch L-to-R could have been anywhere from the mics, the board(s), mixing, mastering, or radio station source, board, pre-amp, EQ..., ... well you get the idea.

Another simple explanation could be that the system is not set up with band equalization as you are familiar with, resulting in the different sound reproduction.

Rob

The 1.5V battery test (mentioned in another reply) is the best way. However, if you can't get to, and separate the speakers from the amp, then the easiest way is to get a cd that has monaural music/vocals on it. Play it, then get your head exactly between the left and right speakers. If the sound seems to be coming from the middle of your head then the speaker polarity is correct. If the sound is spread out -- sounding like it's coming from the left and from the right, then (most likely) the speakers are out-of-phase with each other.

Bob '03 Cobra coupe

"Bob" wrote in news:6k4Bd.13162$ snipped-for-privacy@newsread1.news.pas.earthlink.net:

Additionally, you should do the same between front and rear. It's entirely possible to have the L + R fronts be in phase with each other and the L + R rears to be in phase with each other, but the front pair and rear pair to be out of phase with each other.

Best way to check is with the 1.5 V battery, but you can always do what Bob described with the fader instead of the balance control. Position yourself sideways in the car (looking out the side window) directly between the front and rear speakers, then roll the balance to the side you're facing. Then perform Bob's test "sideways". HTH.

Joe Calypso Green '93 5.0 LX AOD hatch with a few goodies Black '03 Dakota 5.9 R/T CC

Great points, Joe.

There is a test CD put out by Stereophile magazine. It has monaural tracks that are in-phase, and the same stuff but out-of-phase. Using this type of signal, it's really obvious if the speakers' phase is correct.

Bob

"Bob" wrote in news:mShBd.13550$ snipped-for-privacy@newsread1.news.pas.earthlink.net:

That CD is a real good test source. However, for those looking for a mono source, good ol' AM radio works pretty well. ;)

Joe Calypso Green '93 5.0 LX AOD hatch with a few goodies Black '03 Dakota 5.9 R/T CC

An interesting problem with the older Mustangs was that the ground returns for the right and left front speakers were swapped. This caused a real headache when wiring in a new head unit. The test for this you used the aforementioned battery test and jumped across the speaker lead and its return. If they were wired correctly you would hear a "scratchy" noise coming from the speaker. If they were miss wired, as in my case, no sound would be heard. To find the correct return you held one side of the battery on the speaker lead you were testing and tried each return line in sequence until you heard the noise.

Note, at some point in time the factory became aware of this problem and "fixed it" by swapping the speaker power leads around. I found this out by installing a newer factory amplified stereo into my older (and already properly wrung out) factory stereo wiring. This caused the front balance not to work, thinking it was the same old problem I swapped the ground wires on the amplifiers output, which caused the right and left speakers to switch, so I had to put the returns back where they were and swap the power leads instead. So while you are doing your testing make sure the noise you hear is coming from the correct side of the car.

This is the way to do it. Works perfectly.

LJH