What does Nominal Impedance mean?

@ozzy it is rare that a large cabinet speaker is also not sensitive. The reason for the large cabinet is to increase its efficiency and thereby sensitivity. Small speakers are typically more difficult to drive and require greater power to overcome their lack of sensitivity and low impedance curves. Ohm’s law explains these electrical properties but I suspect it will be a little over your head unless you intend to do a deep dive into the subject. 

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.

czairvey,

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

ozzy

@ozzy,

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.

Mike