I've done quite a few tests on my new 2012 21 inch iMac and have concluded that the left speaker has more punch or bass too it than the right speaker. I did this test by going to settings and sliding the speaker balance to the right and left while listening to a song like this. On the iFixit teardown it shows that the left speaker part is larger the the right speaker maybe the left has an added mini subwoofer? This isn't a big issue for me since I use headphones most of the time. Anyone else want to report their findings?