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The under appreciated impedance curve

One thing that a lot of audiophiles don't look at or don't know how to interpret is the impedance curve. I call it the honesty curve too.

Of course, most audiophiles know to look for high imepedance speakers for tubes, and that low impedance speakers are going to be more amplifier demanding.

I also look for:


  • A drop in impedance at 100 Hz at or below 3 Ohms - Indicates "amplifier sensitive"
  • A ragged magnitude instead of simple, clearly defined humps. If the impedance is ragged it indicates highly equalized components.


One speaker which breaks both of these rules was just reviewed at Stereophile, the Wilson Yvette.


https://www.stereophile.com/content/wilson-audio-specialties-yvette-loudspeaker-measurements



Like all things, there are no absolutes but these are the things I look for in a speaker. What do you look for in the impedance curve?
erik_squires
lowrider57's avatar
lowrider57
5,417 posts
 
Erik, I agree this measurement is overlooked by many audiophiles (except by the technically oriented).
I look to see if the curve is relatively flat. As you state, a clearly defined hump is common and usually acceptable.
If the specs of the speaker state 8 ohms nominal, I want to see the curve between 8 ohms and 4 ohms. And if it is close to 8 ohms throughout the frequency spectrum then the rated sensitivity can be given less importance.

I check to see if there are any drastic peaks in the low  frequencies (about 60Hz or less) and then ignore them since they are typically
resonances inside a wood cabinet speaker. At such low frequencies they should not affect bass reproduction.


mesch
3,510 posts
 
I agree that the slopes within the frequency plot should not be too steep. I believe an 8ohm nominal speaker plot should average ~8ohms and not dip below 4 ohms or reach greater than 16 ohms. Often this is not the case. I wish this  and phase angle information, were available for all speakers.  

  

 
audition__audio
1,500 posts
 
I cant think of a single reason why any speaker should be of a lower impedance other than perceived higher power with most S.S. amps. Fact remains that higher impedance speakers are almost universally easier to drive regardless of amplifier type. 

Stereophile has had a long love affair with Wilson. Gives me pause after numerous auditions of Wilson products. 
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