HEDD’s “Closed or Ported” (CoP) innovation is a clever feature to offer two distinct monitoring experiences in one speaker. It is applicable to all of the MK2 speaker range and uses the DSP to make all the necessary adjustments to get the most of either application.
In Ported Mode, the low-end woofer additionally pushes air backward down the port, where lower frequencies remain unfiltered and enhance the bass of the driver’s capability. In general, I think this is the most common speaker design as it allows for punchy bass and more efficiency which translates to a higher maximum SPL.
However, Closed Mode, seals this port and eliminates unwanted phase delays from the port. The result is a cleaner and tighter presentation. It is my preferred way of listening, btw.
The great thing about the MK2 speakers is that you don’t have to make your decision before purchasing. Preference will depend on many factors, especially the room but also application. Maybe you need more volume for a chest-thumping EDM production, but another project requires clean vocal editing. CoP is a really great novelty and is further enhanced by other MK2 features like the HEDD Lineariser, a zero-phase filter.