Speaker Resistance

[MacDaddy]

Hi,

I have a Peavey Duel 212 with, well, two 12" drivers, funnily enough.

The drivers are 8 ohms connected in series which makes a 16 ohm load.

So, to increase the amps flexibility a bit I tried wiring each speaker individually and inputting them into the speaker outs in parallel, two 8 ohm loads would then make a 4 ohm load when using both speaker outputs on the amp.

Odd thing though, when I measure the resistance of the speakers wired in series it measures 16 ohms, however, each speaker on its own only measures 0.8 ohms.

I figured I was just reading things wrong and wired one speaker up and gave it a go with the amp switched for an 8 ohm load. It was unusually quiet, so I figured probably best not to continue, something was clearly not right.

I've rewired speakers cabs before and have never come across this. How can the series resistance of both drivers together measure 16 ohms, but the drivers individually only measure 0.8 ohms?

I look forward to being educated.

 

[crguti]

Re: Speaker Resistance

you're definitely doing something wrong. Are you sure you're using the same ohm scale in your multitester?

 

[uOpt]

Re: Speaker Resistance

You cannot measure speaker resistance with a DC ohmmeter.

 

[Reload in 5]

Re: Speaker Resistance

You cannot measure speaker resistance with a DC ohmmeter.

you can, just not accurately.

you're definitely doing something wrong. Are you sure you're using the same ohm scale in your multitester?

this is my thought also.

 

[ItsaBass]

Re: Speaker Resistance

My first suspicion would be that the decimal was in a different place between the two readings.

 

[MacDaddy]

Re: Speaker Resistance

Yes same scale on the meter.

I realise that measuring speaker resistance/impedence with a multimeter isn't exactly accurate but should provide an indication - that said, the accuracy isn't going to change when measuring one speaker or both in series.

I will try to post some pictures up later with the readings from each and both speakers.

Thanks for replies thus far, appreciated.

 

[uOpt]

Re: Speaker Resistance

I realise that measuring speaker resistance/impedence with a multimeter isn't exactly accurate but should provide an indication - that said, the accuracy isn't going to change when measuring one speaker or both in series.

No, it really doesn't work. You can't measure a coil intended for movements under A/C with a D/C multimeter.

 

[CTN]

Re: Speaker Resistance

No, it really doesn't work. You can't measure a coil intended for movements under A/C with a D/C multimeter.

*shrug* I've done it before, and gotten fairly accurate readings. usually 15.XX for all my 16 ohm speakers.

 

[Reload in 5]

*shrug* I've done it before, and gotten fairly accurate readings. usually 15.XX for all my 16 ohm speakers.

Yeah, I have only done it probably 1000 times. That's not an exaggeration either. I installed car stereos for 5 years and constantly did this to check sub woofers that were "blown" or to check what some idiot had hooked to his 4 ohm stable amp.

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Not sent from a PC......or a red delicious.....but from a robot with a human appearance.

 

[ItsaBass]

Re: Speaker Resistance

You cannot measure speaker resistance with a DC ohmmeter.

No, it really doesn't work. You can't measure a coil intended for movements under A/C with a D/C multimeter.

You of course cannot measure impedance that way, but you can get enough of a reading to gather some basic information about your speaker, and enough predictability of readings to know when something looks right or wrong. A 16 ohm speaker will read near 16 Ohms of resistance on a multimeter, and an 8 Ohm speaker will read near 8 Ohms on a multimeter. Nobody is claiming to be measuring actual impedance here; but an 8 Ohm speaker should definitely not read 0.8 Ohms on a multimeter.

Back to the point, I think there is a problem with the meter or the way it is being used, i.e. it's switching to the wrong range setting for the second reading. Is it a fresh battery? And is it a good quality meter, or one of those $5 or $10 ones from the auto parts store? Those cheap ones can be "fritzy" IME.