Test speaker OHM, only with a multimeter?

[liquidice]

I have fought with JBL for months about finding out the Ohm rating of my JBL Control-1 monitors, and they can never give me a straight answer. Don't bother looking my speakers up, because I've done it all, and the ratings are all over the place, and plus my L/R are Control-1's that I won in a contest years ago working in a pro-audio store, and no one can tell me what series they are. So with that disclaimer, I'm wondering if there is anyway to test my speaker ohm by perhaps plugging them into some sort of machine? JBL told me to take the speaker apart and test at the positive and negative contacts on the woofer itself. Hard part is, to take these things apart, you need a pile of tools and a heat gun to loosen glued together parts. Testing at the terminal on the back gave me wierd readings....sometimes no reading at all. I really don't get it. Would testing through the terminal which goes through a x-over mess it up anyways? Feedback would be great...I'm afraid I'm going damage to my receiver. They are either 4 or 8 ohm, that's as much as I know...which isn't crap obviously. Thanks.

[Big Daddy]

The easiest and least costly approximation requires an Ohm-Meter. It is not scientific, but it may work.

The impedance of speakers usually is either 2 Ohm or 4 Ohm or 8 Ohm or 16 Ohm. Get an Ohm-Meter and measure the DC resistance of the speaker. Round the number to the closest reasonable value. If the measurement is 3 Ohms, then the speaker is 4 Ohm. If the measurement is 13 Ohm, then it is a 16 Ohm speaker.

[liquidice]

I'll give it a whirl again. Maybe I had the meter on a wrong setting when I did this before. I just think it's funny that JBL can't tell this way or that either.

[Blown 4.3]

so. what did ya come up with ?

[richteer]

Note that if you're successful, the reading you'll get from your multimeter will only be the DC resistance. That may (or may not) be wildly different to its nominal resistance with AC at audio frequencies.

[Blown 4.3]

i just Ohm'd my mains, sides and subs. they are just a little under their ratings.
my old mains and small bookshelfs Ohm'd at just over 3 Ohms. they are both rated at 8. the bookshelfs are about 15y/o and the old mains are about 20 y/o.

hmmmm

[zicmubleu]

Originally Posted by richteer

Note that if you're successful, the reading you'll get from your multimeter will only be the DC resistance. That may (or may not) be wildly different to its nominal resistance with AC at audio frequencies.

That is an accurate statement. According to Wikipedia a speaker's impedance is measured over the full audio range it is used for and the lowest value is the rated value, or something along those lines. Also as another person noted you are measuring the crossover circuit couple with the speakers, but this is most likely what you are truly interested in.

If you really have a concern you might try wiring a known resistance speaker in series with your unknown speaker to your amp's output, play a steady tone, if you have a way to do that, and measure the voltage drop across each speaker. Whether to measure with an AC or DC voltage setting on the multimeter probably depends on the meter as well as how the amplifier outputs its signal, I would start with AC anyway. If, a big question, you get some readings you can use that voltage ratio to calculate your speaker rating based on the known speaker. This may sound complicated but it isn't, you would need a jumper to connect the two speakers in series. The speaker with a higher resistance will have a higher voltage reading across it in a series circuit. Always start the meter off in a high range and work your way down to a range that gives you a good reading if it isn't autoranging to start with.

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