Late last year, JBL released the amazing Flip —a $99 tube-shaped speaker that outperformed Jawbone’s $200 Jambox, taking honors as our 2012 Speaker of the Year. Since then, it’s been hard to look at similarly-sized and -shaped speakers without asking what possibly could justify a $100 price premium, so Sync by 50 arrives with a challenge: it needs to somehow deliver twice the sound or other frills to make up the difference. Beyond…