spironical wrote ...
Every year or two CU tests popular speakers, and while most speakers claim
to be 8 ohms, CU finds most to measure 4 ohms. Although CU's opinions
should to be taken with a grain of salt, measurements are measurments, and
not opinions.

"8 ohms" sounds like the "nominal rating". While the speaker is
likely actually 8 ohms at some point, the impedance is never
uniform across the whole frequency spectrum. Nominal ratings
are just a guide to tell you what the design impedance was.

CU's measurement of 4 ohms sounds like the minimum impedance
at some (unspecified) frequency. This seems normal to me. Look
at any impedance curve and you can see that the variation between
minimum and maximum impedance can sometimes be 2x or even 4x.

The fact that CU is reporting the minimum impedance (without any
apparent explanation or context) is just indicative of their questionable
understanding, judgement, and reliability in technical areas.

No offense, but the notion that "measurements are measurements
not opinions" is not a safe world-view to subscribe to. ALWAYS
question how the measurements were made and what is the hidden
agenda of the person reporting them. In CU's case, reporting 4 ohms
for nominally-rated 8 ohm speakers makes them look like consumer
champions giving you valuable information worth paying for. While
in reality, they are reporting perfectly normal phenomenon.