Mininum Impedence Vs. Nominal

[newtoaudio90]

Whats the difference between Nominal Impedence and Minimum?

When looking at speakers they often give ONE value, i.e. Impedence =8ohm.

Some speakers I looking at currently have a Nominal impedence of 8ohm and a minimum of 4.

Which value should I be looking at?

Thanks again

 

[Irvrobinson]

The single value in most speaker specs is the nominal impedance, and seems generally intended to facilitate amp matching. For example, some amps aren't rated for 4 ohm speakers, though they will often at least function with 4 ohm speakers. This is especially an issue for some tube amps. The minimum impedance is more important in my mind, as a speaker with a very low minimum impedance, like 2 ohms, may take a really powerful and well-engineered amp to properly drive it.

 

[vinicior]

Hi

An impedance or minimum impedance is the value of impedance of speaker and nominal impedance will give the value of impedance with radio frequency antenna or wires.

 

[TLS Guy]

An impedance or minimum impedance is the value of impedance of speaker and nominal impedance will give the value of impedance with radio frequency antenna or wires.

What nonsense!

The nominal impedance means nothing.

You really need to know the impedance curve of a speaker.

You could say the nominal impedance of a speaker like the one above is 8 ohms. However where the power is it is four ohms or less.

The minimum impedance is about 3.5 ohms in the audio range. The rule of thumb is to consider the actual impedance of a speaker, if you don't know the curve is minimum impedance plus 10%. For this speaker this would work out well, as this should be considered a four ohm speaker.

 

[Irvrobinson]

What nonsense!

He was obviously joking. As I said, the minimum impedance is the important spec, although it is also important to know if and where a speaker presents a highly capacitive load. A lot of poorly designed amplifiers don't like that.