about 6 months ago, although I can't find the thread cause everytime I search for a discussion in this new forum it brings me to the digital camera review site. But it's basically cause they're so close to your ear, they don't need big speaker drivers to fill a room with bass-mids-and highs, just that small space between the headphone drivers and your ears. I wish I could describe it in more detail, but a guy named Haoleb that used to go t this site explained it quite well. I too find it really amazing how headphones sound so good, can't wait to get my Grado SR-60's!

-Joey