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.
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:
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?
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?