Well, if you imagine glare on a window from the sun and you can't see clearly because your eyes are squinting. The upper frequencies if they have "glare" is similar. Theres an extra artificial "sheen" which can be annoying. This is normally cause by irregular peaks. Makes your ears squint! IMO the HE500's have a little bit "glare" but the LCD2.2 don't.
(don't ask me what "sheen" means in audio terms )