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Speaker ohms.

The biggest problem with nominal impedance ratings like 4 ohm or 8 ohm is the manufacturer gets to make the determination. There are standards for rating 4 ohm and 8 ohm speakers, but it is easy to find speakers that break the rules. Take my current speakers for example. They are rated at 6 Ohms, which may make you think they can be driven by a 30W receiver that claims it can drive 4 Ohm loads. Well the problem with that is, they are only 86Db efficient, so they require more watts to get them moving. Then there's that impedance dip to 1.1 Ohms that few power amps can deal with. Most receivers or even stand alone power amps are not built to push power to a 1 Ohm load. Then there's the infamous Infinity Kappa 9s, rated at 4-6 Ohms, but with a nasty dip that can hit slightly below 1 ohm. They earned a reputation as amp killers. Not all 4 Ohm and 8 Ohm speakers are created equal, and some "8 Ohm" or "4 Ohm" speakers truly aren't
 
I have a couple of questions relative to the topic.
Which impedance number is dominant when you have, lets say a 3-way crossover with a listed impedance level of 8 Ohms but the actual speakers (drivers) are rated at ie. Woofer 8 Ohms, Mid Range 4 Ohms, Tweeter 6 Ohms. ?
I've also wondered that if when faced with a impedance concern such as connecting a vintage 8 ohm Amp to 4 Ohm speakers, could you compensate by using thin speaker wire? It's not something I plan nor ever intend to do I'm just being curious. Thanks!
 
CrazyTrain said:
I have a couple of questions relative to the topic.
Which impedance number is dominant when you have, lets say a 3-way crossover with a listed impedance level of 8 Ohms but the actual speakers (drivers) are rated at ie. Woofer 8 Ohms, Mid Range 4 Ohms, Tweeter 6 Ohms. ?
I've also wondered that if when faced with a impedance concern such as connecting a vintage 8 ohm Amp to 4 Ohm speakers, could you compensate by using thin speaker wire? It's not something I plan nor ever intend to do I'm just being curious. Thanks!
Click to expand...

The issue is that impedance changes with frequency so the total load the amp will see depends upon the frequency spectrum of the music being played. And that will change from instant to instant. The only way your amp would see the impedance of an individual driver would be to feed the amp with a single tone from a signal generator.
 
Dan13105 said:
The biggest problem with nominal impedance ratings like 4 ohm or 8 ohm is the manufacturer gets to make the determination. (...)
Click to expand...

Back in the day over here the DIN45500 standard for hifi equipment required speakers not to dip more than (-)20 % below their nominal impedance - but of course even back then not all models would comply to that.

Greetings from Munich!

Manfred / lini
 
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