8 Ohm Speakers read less than 8 ohms

Aaron Bilger

Aaron Bilger

Audioholic
So I have some speakers that say they are 8 ohms I test them with my fluke tester on the ohms setting test the speakers from the terminals and they read 6.6 ohms they are 2 way speakers I have them 2 speakers on 1 channel and the other 2 on the 2nd channel running to be 4 ohms but they both read together not connected to the amp @ 3.3 ohms and the amp will only do down to 4 ohms it's the crown XLi 800 but I don't go loud with them. Is this just gonna cause damage since I been using them like this for 2 months and no problems have occurred.
 
ski2xblack

ski2xblack

Audioholic Field Marshall
The lower impedance measurements (dcr? 3.3 ohms at what frequency?) you're noting are to be expected, particularly if you're comparing to "nominal" ratings. Burdening your amp with high current demands will result in excessive heat, and parallel wiring will reduce the impedance that the amp sees and thus increase current demands, so there's that. Heat is no bueno for the longevity of your electronics.

3.3 ohms isn't really that low for a fan cooled Crown amp, particularly if you don't blast it, but even if it works for now it's probably not something you'll want to stick with indefinitely.
 
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P

PENG

Audioholic Slumlord
So I have some speakers that say they are 8 ohms I test them with my fluke tester on the ohms setting test the speakers from the terminals and they read 6.6 ohms they are 2 way speakers I have them 2 speakers on 1 channel and the other 2 on the 2nd channel running to be 4 ohms but they both read together not connected to the amp @ 3.3 ohms and the amp will only do down to 4 ohms it's the crown XLi 800 but I don't go loud with them. Is this just gonna cause damage since I been using them like this for 2 months and no problems have occurred.
Your Fluke meter can measure resistance, not impedance. Impedance varies with frequency so a typical Fluke multimeter with a D.C. output is not going to cut it. If the resistance (d.c.) is 6.6 ohms, I am pretty sure the average impedance over the frequency range of 20 to 20,000 Hz will likely be higher than 8 ohms.
 
Aaron Bilger

Aaron Bilger

Audioholic
Your Fluke meter can measure resistance, not impedance. Impedance varies with frequency so a typical Fluke multimeter with a D.C. output is not going to cut it. If the resistance (d.c.) is 6.6 ohms, I am pretty sure the average impedance over the frequency range of 20 to 20,000 Hz will likely be higher than 8 ohms.
No it measures more than just resistance in ohms it had no power going to them everything was discounted. I know what the ohms would be I used the Fluke 110 that I just bought at lowes.
 
TLS Guy

TLS Guy

Seriously, I have no life.
No it measures more than just resistance in ohms it had no power going to them everything was discounted. I know what the ohms would be I used the Fluke 110 that I just bought at lowes.
Your fluke meter measures DC resistance not impedance. They are in no way the same thing.

Here is the impedance curve of an 8 ohm speaker.


The blue line is the impedance. The first hump is the impedance rise from the tuning of the ported cabinet. Then the woofer's impedance rises with frequency and then drops as the tweeter takes over.

If you measure this speaker with your fluke meter it will read 6.2 ohms which is the DC resistance of the woofer voice coil. You will not measure the DC resistance of the tweeter as there is always at least one cap in series with the tweeter. Caps do not pass DC current, so your meter will not see the tweeter at all.

Bottom line is that you need to review the physics of impedance and AC circuits as well as at least the elements of crossover topology before making anymore posts like this.
 
P

PENG

Audioholic Slumlord
No it measures more than just resistance in ohms it had no power going to them everything was discounted. I know what the ohms would be I used the Fluke 110 that I just bought at lowes.
Of course your Fluke meter can measure more than just resistance, it is a mult-meter afterall. We are saying it does not measure impedance. impedance varies with frequency, and thanks to TLSG you can now see an example of the impedance vs frequency plot. Obviously if you do the same with your speakers, it will look different.

Again, the average impedance of your speaker will likely be well above 8 ohms.
 
Aaron Bilger

Aaron Bilger

Audioholic
Ok then how do I measure the ohms of my speakers then?
 
TLS Guy

TLS Guy

Seriously, I have no life.
What speakers are we talking about?
It really does not matter. The point is that to measure the impedance of any speaker you need a dynamic and not a static measuring system.
 
everettT

everettT

Audioholic Spartan
It really does not matter. The point is that to measure the impedance of any speaker you need a dynamic and not a static measuring system.
Was just curious if maybe they had been measured by a 3rd Party.
 
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