OK, minor correction. Questions for you.

1. How long does it take for that capacitor to charge (assume 4.7uF 50V)?

2. How long would it take to fry the average tweeter?

3. How long would it take to fry the average woofer?

4. Is your 14.4v battery then more likely to blow the woofer or tweeter?

I'm testing you to establish the relevance of the minor correction.

That is exactly why I asked the question originally. I always use the marked wire as positive but a lot of the jobs that I have to re-do are ones from years ago before forums like this one existed and pro-logic was King.

There are some great Ideas here. I especially like the wire touching the cone Idea. Seems simple enough.

Only question is- will the cone only move when correct polarity is present or will it only move in one direction (in or out?)when correct?

When the polarity is correct, the driver will move out. You can also check polarity without pulling the loudspeakers with a polarity checker. I use an "old scool" unit from my 12v days that was built by Navone. It requires playing a specific CD track on the system while performing the test. There are other units that include a signal generator instead of the CD, Goldline makes one of those. This approach can be a heck of a lot quicker on a larger install. You just hold the tester near the speaker and look for a green or red light.

jcmitch

[Link: davidnavone.com]

[Link: gold-line.com]

"Correct" is when all speaker cones move in the same ditrection with the battery test done with the same terminal touching the same wire color/stripe/ribs/etc.

In other words, the cone will move with the battery connected either way; the idea is that all the cones in the system move the same way with the same voltage polarity (relative phase).

The majority agree that when the cone moves into the room, the terminal that causes that motion should be marked as + (absolute phase).

Remember: do the battery test with a quick touch of the battery, not a continuous connection. You don't want to heat up a voice coil. I suggest enlisting the help of a second person.

if all else fails you cold hook them up one pair at a time and listen to them.

Sorry if I rufflled your feathers Tom. Wasn't intentional.

Not at all! You did raise a point of the charge time of the crossover cap, saying "all the time the cap is charging, current flows" or something like that. True. However, I hoped you would clarify that by answering the questions. The answer will make the charge time irrelevant. Let me elaborate by answering the questions:

1. How long does it take for that capacitor to charge (assume 4.7uF 50V)?

A. Not calculated precisely, but fractions of a second ("milliseconds").

2. How long would it take to fry the average tweeter?

A. Just a little more than instantly if it has lots of DC *directly attached* to it. Tiny wire gauge. No power handling capability to speak of. Ferrofluid helps, but the tweeter in normal operation, although handling lots of the crispness and definition of the sound, handles only a fraction of the *power* that is applied to the cabinet.

3. How long would it take to fry the average woofer?

A. Connected more or less directly to the input terminals, a 14V several amp capacity drill battery could probably do it in 2 to 10 seconds.

4. Is your 14.4v battery then more likely to blow the woofer or tweeter?

A. The woofer, since it is usually direct to the input terminals. The tweeter can almost not be snuffed due to the series capacitance.

I'm sure someone could argue that "I've seen.....and it really happened......" I've repaired speaker cabinets for nearly 30 years and I know that there is always the exception to the rule, but it would be pretty rare unless your cabinet / in ceiling speaker was wired in an unorthodox fashion.

Warren, I don't think you can get consistent tweeter failures with a battery. I'd be surprised if you could get one at all.

Thanks for keeping the conversation active.

Here are my answers:

1. In my opinion (and theoretically), assuming no series resistance and infinite current capability, the charging time would be infinitesimal, and the current infinite. Of course, the tweeter itself becomes the series resistance.

Here is the math: Given: 8 ohm resistor, 4.7uF cap, 14.4V source
Time constant = 0.0000376 seconds; Max current - 1.8 amperes

2. It's hard to say, but the high initial current is what concerns me.

3. With (assuming) a series inductor in the low-pass crossover filter, the collapsing field could induce a high-voltage peak.

4. If I caught anyone using more than a 1.5 v battery on my speakers, I'd test their polarity with . . . never mind.

Yes, but what if you are the only installer in his city so he doesn't have that option?

Ouch!

Take a 9 volt battery, or 1.5, with one of the input wires to the speaker connected to the - terminal of the batter, momentarily touch the other wire to the + terminal of the battery while watching the direction of the cone movement. If the cone pushes outward, you know that wire is the + one. If the cone seems to move inside, then it is -.

Back to the 14.4 volt issue for a moment.... something to consider.

A speaker rated at at least 30 watts, which would include most decent quality ceiling speakers will actually be hit with a higher voltage from its amplifier if driven to full power. It takes about 15.5 volts to deliver 30 watts into an 8 ohm load.

That also means it will be subject to more inrush current from the amplifier than the battery as well.... and have to deal with it on a continuous basis.

That only leaves the DC question. Certainly a battery left connected to a speaker will burn the voice coil. We were talking about popping speakers for a momentary test. Quickly tapping the battery terminal just isn't going to provide enough time to overheat the wiring.

If you are dealing with El Cheapo speakers....I would be more concerned about it.

Wow. Where else can you read 2 pages on how to pop a speaker with a battery? Or how to "Y" a flasher? Or how far DVI goes? Or why velcroing remotes to a plank is a bad idea?

No sarcasm, this is not a bad thing. One can learn our entire industy just by reading this forum.

Doug @ HomeWorks

Another option from Gold Line will cost you about $300 but it works. the APT2 is a two piece device that generates a tone the uses a built in condensor mic to test for polarity in speakers AND processing equip. Full Compass and I'm sure many others sell it.

What if the speakers are on a different floor than the gear?