Not sure what adapter to use

Use a fuse . Do experiments while a diode and a resistor limit the power. Ring may be GND, tip is +12v. Sneak up on it . Start with 100 ohms in series. Then 33 ohms. If it makes sounds, decrease the protection. Experiment. The series protections of fuse, diodes and R will save your bacon. Enjoy the experimental progress until success is yours.

Look up the model numbers on the web? More than 90% of these things are Center-Pin-Positive (CPP). If you have to guess that's the way I'd go.

That's strange. Sure, the unit doesn't care what the voltage on the other side of the power supply is.

More is better. If the supply can't supply the current you'll likely notice distortion before you have too much fire. ;-) Make sure nothing gets hot.

As with many things, the size of the connector matters, also. Many look the same but there are many "standard" sizes of these things.

It doesn't matter what the input is as long as you get the correct output. If your device needs 12 volts @ 500 ma. (.5 A) then your adaptor that supplies that will be OK. (You need the correct plariity.) Maybe the symbol (O) with a + at the O is there, this indicates that the center is possitive. You were not too clear on the other requirements.

Tom

As mentioned already, for most "cylinder/coaxial" type adapters, the center is positive. If you can open the speakers and check the circuitry, you may find a hint from a polarized electrolytic cap, the way an LED is wired, etc.

-- Roberto Waltman

I don't know where this "most" comes from, someone else said it too. I certainly wouldn't trust it. I'm getting the impression from recent comments (elsewhere) that maybe there was an attempt in recent years to "standardize" but that sure isn't the case from the past. Which means you never know.

I sure wouldn't trust something without verifying. Just a couple of weeks ago I bought an ipaq PDA at a garage sale, with the docking station but no ac adapter. I had no qualms about assuming the adapter was 5v (at the very least, if I was wrong it would be because I guessed a too low voltage, which won't hurt something) but a search didn't show anything that I'd trust. So I used the usb connector in the base to find which of the ac adapter pins was ground, and thus verified what the search results said.

It is pretty easy once the speaker is open. On the other hand, some of those computer speakers seem quite difficult to open. I just smashed one open a few weeks ago, though in that case I merely wanted the small amplifier for something else rather than a working speaker.

Michael

Certainly not all DC barrel connectors are CPP but easily 90% (add another nine) are.

If one knew what they were doing, an ohm meter might tell the positive terminal, too. I'd want to play with it before telling someone unfamiliar with such circuits what was what.