I like Brent Butterworth's postings/observations. Here's an article on his musings about testing the Harmon curve :
Are There Valid Objections to the Harman Curve?
https://www.soundstagesolo.com/index.php/features/318-are-there-valid-objections-to-the-harman-curve
Are There Valid Objections to the Harman Curve?
https://www.soundstagesolo.com/index.php/features/318-are-there-valid-objections-to-the-harman-curve