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?

ozzy

128x128ozzy

Lower impedance = higher current = more output.  Since most solid state amplifiers can drive 4 Ohms without issue as a speaker designer I might chose a lower impedance driver to give me more output. Especially in matching say a woofer to tweeter, when tweeters usually have more output for the same voltage. 

AFAIK there's no actual standard for rating your speakers, and some like modern KEF speakers, are so optimistic in rating their speakers that you can't use them to pick matching amps at all. 

jjss49, erik_squires,

Thanks for that very good information. It’s interesting and confusing at the same time.

ozzy

At Townshend Audio we match the average nominal speaker impedance (around 8oHms) with the impedance of the amplifier using Isolda 'impedance matched' Speaker Cable. Here we explore the reasoning behind our cable products: https://townshendcable.com/ 

Our Analysis uses a test set-up to prove how mismatched speaker cables will cause audible differences between a range of cables.

Thanks for your time.

Harriet Townshend

Yes Ozzy, this is the micro-site for the Townshend F1 and Isolda Speaker cables. Max tried to understand the clear differences he heard when hearing matched impedance cables Vs unmatched impedance cable.

Dedicated to understanding the phenomenon and spending a large chunk of his last years researching and testing.

His videos on You Tube called 'Geometry Matters' charts his reasoning.

Harriet