The JM Labs mini utopia you referenced are great speakers. Here's the Frequency Response plot for that speaker:



There are some other very high end speakers which also use supertweeters, Tannoy, Harbeth, VMPS, PSB Platinum Range speakers, Coincident ... you may recognize some of the greatest speakers out there.



Enjoy the Music. Trust your ears. Laugh at Folks Who Claim to Know it All.