Multimeter DC resistance vs. specified impedance - what's the difference?

On this episode of Ask The Expert we're following on from the episode about impedance, explaining what to watch out for when measuring impedance yourself at home.


In this episode of Ask The Expert we address a follow-up question to our episode on impedance.

If you have a question for our experts – whether that be a follow-up question to a previous episode or something that we haven't covered yet – don't hesitate to send it to us via the 'Send us your questions' form at the bottom of this page, and we'll do our best to answer it for you in a coming episode.


I have a pair of Dynaudio Contour 20. The impedance on my multimeter shows 8 ohms but in the specifications, it says 4 ohms. What are they?

When you are measuring the loudspeaker with a multimeter, you are actually measuring what's called DC resistance. This is the resistance or impedance at 0Hz and – as we explained in an earlier episode – impedance varies by frequency.

When we specify impedance, we do so based on the lowest point, which might be different to that of the DC resistance i.e the 0 Hz resistance.

In this specific case, you have a loudspeaker that measures 8 ohms at DC, but that goes lower (4 ohms) at a different place in the frequency response.

This is why we specify this speaker at 4 ohms, even though the DC resistance is 8 ohms.


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