After spending considerable effort at room treatment to achieve a flat response from my main speakers, and getting VERY close to ruler-flat, I was dismayed when I measured my rather decent sounding headphones with Room EQ Wizard. They were nowhere near flat, looking like the 'better' curves mentioned in the linked web site on this thread. Headphones, I used to think, were supposed to sound superior to loudspeakers. But in my experience, they don't. I MUCH prefer the sound of my loudspeakers to the sound from the several pairs of headphones that I own.