The classic grot-box check. One driver, no crossover, no bass reflex port. No low end, no top end - just naked midrange. Why does that matter? Because this is where 90% of the song lives: vocal, snare, melody. Cubes mimic the way your track will translate to a phone, laptop, or Bluetooth speaker.
Blind spot:
Working on them for hours is physically uncomfortable, and it is easy to misjudge the balance of high-frequency and low-frequency instruments. But there is an important upside: switching to small, midrange-focused speakers at a low level is a great way to refresh your hearing during long sessions, giving your ears a break from aggressive highs and pumped-up lows.