I just noticed the M80OW are sealed. No ports. Sorry about misleading you. The M60s are sealed as well.

The smaller models consisting of the M5, M3, M2 are all ported.

Strangely, the M0 were also sealed.

Sealed is cool. Less distorted bass.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated