The lowest impedance is important to know so that you can get some idea about what kind of load they will present to your amp(s).
Stat panels look electrically like capacitors, and so their lowest impedance is usually very small at high frequencies.
Cone speakers look electrically like inductors, so their lowest impedance is typically at low frequencies. If a speaker has a nominal impedance of 8 Ohms, its frequency dependent impedance range from 2 to 32, or 4 to 20, or something else. You’re interested in both the nominal impedance AND the low impedance.
The efficiency is good to know too (so that you have some idea about how loud they will be with your amp). The spec is given as so many dBA per Watt per meter at a given frequency, often 1000 Hz. Efficiency of various models typically runs from 80 dBA/W/m for lower efficiency speakers to as much as 105 dBA/W/m for some VERY efficient models. At 80 dB/w/m you need a fairly powerful amp to get good volume in medium to large rooms. At 105 dB/Wm you can get loud with a very modestly powered amp.
So the specs can help you rule things in or out, but they don’t tell you much about how two speakers with similar specs will sound when played in comparison.
...to extend the @Another Johnson point, I already owned Luxman amps when I considered the Magico A5 change. The impedance dip noted by Atkinson's tech review was cautionary, so I contacted Luxman directly to see if they had concerns. They actually contacted Magico to discuss the concept (I was told). It took about a week and a half, but JP at Luxy replied and green-lighted the match. I like this set-up quite a lot, actually. So, yes...the measurements do matter to me, and although I would give my ears and listening needs/habits the final word, it's nice to know you're not working against yourself in trying to get the best you can out of any given pairing...or seeking a quality level that is technically sub-optimal.
Yes and when I build my own speakers I would be completely in the dark without them. Can't design a speaker by ear, at least I can't. There is no way to see exactly what is happening as you make changes to dial things in.
The actual changes are simulated in LEAP based on raw driver measurements mounted in the intended enclosure. You use these for the crossover design. If needed after the changes you remeasure and if you have reliable measurement technique they should be very close to the simulation.
As a matter of fact I purchased my Performa F 206's without a listening session. The local dealer didn't have a pair to demo so I took the leap. Glad I did love them!
Speaker measurements are probably more important than those for electronics, but all measurements are capable of being 'fudged' with incomplete information on how they were made. They can only be a guide. I don't believe electronic component measurements do the consumer any good at all except for perhaps the wattage of a power amp. Measurements can just be manipulated so easily. That's why they should stay in the design lab.
Speaker measurements are probably more important than those for electronics, but all measurements are capable of being 'fudged' with incomplete information on how they were made. They can only be a guide. I don't believe electronic component measurements do the consumer any good at all except for perhaps the wattage of a power amp. Measurements can just be manipulated so easily. That's why they should stay in the design lab.
Measurements are starting points, they can tell you about speaker\driver behavior, but in the end, the ears determine (when possible try at home before you buy).
Measurements are fun but mostly entertainment value to me. If it's meaningful, you can hear it anyways - so why allow an instrument / procedure to interpret it (and then you pile your own interpretations on top of THAT) instead of your ears. I say "mostly" because it's nice to know up front if something doesn't meet spec in a significant parameter - like sensitivity for speakers, gain for phono stage, power for amplifiers, output level for cartridges. You'd figure this out in your system, but it can be a good warning before acquisition.
I already know I prefer tube components with their higher amounts distortion. I know I prefer vinyl over digital; same deal. I get that some will try to dig into the minutiae of the harmonic spectrum (etc) to explain why this is still good, but at the end of the day that's just more entertainment value. I steer my audio ship by subjective evaluations, not objective.
* For specific, targeted applications like tube testing, measurements can be extremely valuable.
