FAO Mike

[tribi9]

Dumb question...

Bought this guy recently....

Hey Mike, what do I set the dial on my multimeter to check the impedance of a speaker? Which inputs do the cables go in?

Cheers n' thx in advance.

[Mike]

200 ohms.

See the bottom left quadrant, That symbol (omega) is the symbol for ohms.

Put your black lead in COM and the red one in the whole above it.

If you touch them together they should read 0. apart 1 or OOR meaning infinite impedance.

Resistance of a speaker comes out slightly less than it's impedance. So 6 ohms means it's an 8 ohm impedance driver

[Doog]

Stupid Q no.2:

What's the difference between impedance and resistance?

[tribi9]

I think my Multimeter is fucked. When I put it on 200, I do get the 1, but when I touch them together it reads 00.5?? And when I try taking a reading, it just starts flashing numbers??

WTF?

Thx for your help tho'

[Mike]

I think my Multimeter is fucked. When I put it on 200, I do get the 1, but when I touch them together it reads 00.5?? ANd when I try taking a reading, it just starts flashing numbers??

WTF?

Thx for your help tho'

Hmm. Have you got a resistor you could try and measure? Check they're plugged in ok and turn them off and on.

[Mike]

Stupid Q no.2:

What's the difference between impedance and resistance?

Impedance is a frequency dependent quality, resistance is not. A resistor has the same resistance no matter what frequency signal you pass through it (reactance is different but that's another story), speaker impedance varies depending on the frequency of the signal you're passing through it.

[Doog]

So if you were using a speaker for a chunky bass amp and then a... I dunno, BANJO amp, it would yield a different impedance?

I take it it doesn't vary a huge amount, lest output transformers be exploding all over the world?

[Mike]

yeah it just varies a bit across the audio frequencies. The multimeter is using a special means to measure the resistance based upon ohms law which is out of the frequency of guitar sounds (i think it's actually DC) which explains the difference.

[tribi9]

If I set it on 20K I can read a pickup I got laying around here. It shows me 7.21. But yeah on 200 nothing? Fucking cheap Multimeter

[Mike]

Nah that's fine, since the pickup is out of the range of the 200 setting.

200 ohms is the MAX that setting can read, which should be fine for a speaker.

So what happens when you click back to 200 and read the speaker? Nothing? or 1?

That could mean your speaker is fucked.

Also try the diode setting - the triangle with line across the end. Touch the tips and see what happens on teh screen (that's continuity) and check for continuity across the speaker terminals.

[tribi9]

On the diode setting when I touch the tips together it reads Zero. On the 200 when I try to get a read on the speaker the numbers just start flashing.

The speaker is fine, its actually mounted on a working amp.

[Mike]

Disconnect the speaker terminals from the amp before taking the measurement.

[tribi9]

Cool, Ill try that but not til later cuz they're soldered and Im going to bed. Its almost freaking morning now.



Cheers Mike and thx for your help again.

[Mike]

No worries.

Those multimeters aren't the best, I have one the same that came free with a toolkit I bought, but they do the job in a snip.

I have one of these I'm really happy with, it's amazing.



My friend Jai also scored me an oscilloscope.

[tribi9]

Nice, now that's a pro looking meter!

[Ninja Mike 808]

I have a very similar one to Tribi9's... When it blinks it means that you're either too high or too low. The idea is to set the switch above what the reading should be. It's weird, though...

[Mike]

No speaker I've ever seen is greater than 200 ohms.

Either it being "in circuit" is causing a problem, or the probes aren't making contact well enough.