What does Nominal Impedance mean?

What does Nominal Impedance mean?

I’m trying to decide on some new speakers (Clarisys Minute). They are rated at 86-88 sensitivity and a nominal impedance of 3.5 flat. Although graphs show it about 6 ohms from 20hz-500hz and at 2Khz and above about 3 ohms.

My present speakers, Focal Sopra 2 are rated as 91 sensitivity and 8-ohm nominal impedance, but minimum is 3 ohms.

So, I am presently using Bob Carver 350 amps (rated as 350 Amps/channel 8 ohm and 400 watts /channel 4 ohm) which are tube mono blocks. and I like to crank it up at times!

Can someone explain about Nominal Impedance and if my amp(s) will have a problem driving the Clarisys Minute speakers?



Incidentally I have never seen a speaker whose impedence measures a flat 2.5-3 ohms over 100-10k Hz.  Have you?

I have the Thiel 3.6's. From Stereophile:


Impedance is a combination of linear R (resistance) and non-linear X (reactance)

A Reactance is a combination of Inductive and capacitive components. In the world of complex algebra the impedance Z is represented by = R + jX. In case of the DC, X component is null so the Impedance in this case is linear resistance R.

Inductive component impedance is known as wL where w is frequency and L is Inductance. 

Capacitive component impedance is known as 1/wC where C is capacitance

Overall Z = R + j(1/wC + wL) where j is directional vector

Notably, with increase of frequency Inductive component increases while capacitive component decreases. that means that on DC capacitor will have an infinite impedance and Inductor will act like short circuit.


Wow! Interesting. Most of this is over my head. I have a business degree.



I think nominal impedance means the industry standard. Impedance should not fluctuate more then 8 or 9% from the standard. I.E. An 8Ohm speaker should be no less then 6Ohms, a 4Ohm speaker should be no less then 3Ohms, if they follow the standard.


I vaguely remember that the speaker industry standard rating of impedance as what it is at 1000Hz.  Which is kind of silly because the impedance is usually all over the place unless the speakers use series crossovers.