What if a high end speaker measures really badly?

It could be the measurement was not done correctly.  Here is the freq. response of the Thiel CS2.4 done by Stereophile.  It doesn't look very good, but the speakers are very neutral and sound quite good.

@andy2 - That’s kind of a weird graph, I think the bass response is incorrect, it’s way too flat to be real.

On another note, I’m afraid I’m going to have to disagree with you. The two times I’ve heard those speakers I was completely unable to listen too them. They sounded much like the Triangles to me and painfully bright.

I know many Thiel lovers here will disagree with me, and that’s fine, I know I’m in the minority. I have to wonder if their charm isn’t at lower listening levels or if I made the mistake of listening with too much toe-in?

Here is the freq. response of the Thiel CS2.4 done by Stereophile. It doesn’t look very good, but the speakers are very neutral and sound quite good.

This is not "neutral and sound quite good". Perceptively, this is another episode of V curve-ish crap that will have appeal to some guy who’s forged in the flames of cheap Klipsch or other lousy focals.

I have ignored the Thiel thread until now (let y’all fan boys rejoice in your own lil pond gleefully), but, you decided to bring it to another different kind of thread...where the truth may get spoken. Sorry to burst your bubble.

But who said the measurement must be linear? Remember popularity of equalizers? And how many people liked V-shape? A lot of music is poorly recorded and can benefit from correction. Enter this speaker. It is basically an equalizer, i bet it sounds great with some music and awful with others. Some people will love it and some will hate its sound. It has clear bump in low region, some peak at highs and dip in the middle. Probably good one for classic rock ;-)

This is why I like measurements. I can filter out speakers I definitely will not like just by looking at the frequency response graph. And select those I most probably will enjoy.

In today’s world of digital audio, sound can be tweaked pretty much any way you want it to be.

So it’s no longer the end of the world if measurements stray from textbook perfect.

As long as the speakers are up to the task of filling the room with sound up to desired SPL levels without distorting and the amp is up to the task of driving the speakers well, you are in a good place.

Maybe just have a handle on dispersion pattern of specific models in order to be well informed about what to expect there. This is one example of where measurements can help.

Toss in some proper DSP like that available in Roon software for example and the sonic details are yours to adjust however you see fit .

Having said that, good measurements are typically an indicator of good design and implementation and that is always good things to have working for you out of the gate.