8 ohm speakers reads 10 ohms

Bill Quinn · Post by **Bill Quinn** » 24 Dec 2023 9:16 am

Any ideas why an 8 ohm speaker would read 10? Vintage speaker that I got for a song, sounds fine but have only used it at home so far.

Stephen Cowell · Post by **Stephen Cowell** » 24 Dec 2023 8:01 pm

Normally they read 20% *less* ohms... so, too much for an 8, not enough for a 16.

If the voice coil's been toasted that will bring up the ohms... give it a sniff, watch for that burnt enamel smell.

Otherwise, run it 'till it quits!

Donny Hinson · Post by **Donny Hinson** » 25 Dec 2023 6:39 am

I suspect that what you have is actually a 12 ohm speaker. Odd impedances like 12 ohms or 6 ohms are rare, but not unheard of, and what you have may not be a guitar amp speaker. As I recall, some of the old home stereo consoles from the 1950's and 1960's used 12 ohm speakers.

Larry Hobson · Post by **Larry Hobson** » 25 Dec 2023 3:15 pm

Faulty meter or meter leads. ? "0" the meter if is possible. Also Connect the two leads together to verify a "0" reading . Then ohm out the speaker.

Bill A. Moore · Post by **Bill A. Moore** » 25 Dec 2023 4:26 pm

I bought a JBL D120 speaker from a fellow here "as is, high impedence". It read about 20 ohms when I got it, I think, so I hooked it to one side of my "shop" stereo", and let's it play all day. I checked the next morning, and found it read 10 ohms. Doing a little checking, I found that JBL actually sold speakers labeled 8-16 ohm!
I used it for a while connected for an 8 ohm load, and it sounded great, eventually sold it because of the weight.

Marco Schouten · Post by **Marco Schouten** » 26 Dec 2023 2:42 pm

But isn't the resistance depending on the frequency of the signal?

Larry Hobson · Post by **Larry Hobson** » 26 Dec 2023 5:17 pm

Yes but it's called impedance .

Stephen Cowell · Post by **Stephen Cowell** » 26 Dec 2023 8:00 pm

Marco Schouten wrote:But isn't the resistance depending on the frequency of the signal?

Yes... the AC component is called 'reactance'... the combination is impedance. If you look at a real graph of a real speaker it goes crazy, with a dip at the resonant frequency. They're rated 'nominal' impedance, which gives folks a target to shoot for.

For our purposes when we check a speaker we're looking for a DC resistance about 70% of the nominal... this is close enough to tell the difference between a 4, 8, and 16 ohm speaker. Speakers can be re-coned with different impedance voice coils... so trust but verify.

Post by **Dave Mudgett** » 26 Dec 2023 10:46 pm

Resistance does not, by definition, depend on frequency. Capacitive and inductive reactance depend on frequency. Capacitive reactance goes down as frequency goes up, inductive reactance goes up as frequency goes up. The three of these compose what is known as complex impedance. My usual rule-of-thumb of resistance/impedance for guitar speakers is about 0.8, but it can vary. But what I see is usually something like a 3.2 Ohm resistance in an old 4 Ohm Champ speaker or a 6.4 Ohm resistance in an old 8 Ohm Jensen.

I have seen 12 Ohm speakers. Old Jensens and so on out of, for example, old film players and other odd audiovisual equipment mostly. I used to see this stuff in salvage a lot. Years ago, I bought a palette load of old salvage A/V equipment for the cabs and speakers. Used some, gave some to friends for projects, and so on. Mostly solid-state amps, but the speakers an cabs were real nice for amp projects. Several of those speakers were 12 Ohm, there were some 16 Ohm, very few 8 Ohm.