I bought a pair of reference 3a mm generation 2 and the bass ports have fallen inside. I can't figure out if they should be downwards or upwards.
Hmmm...just googled the model and saw a rear view of the box: upwards! (the hole)
It shouldn't have much difference if up or down in terms of tuning, however facing up is preferred to stop curious young ones putting lego into the speaker cabinet, just make sure whatever way you choose that the end of the port is not firing into a bracing panel and being choked.