This debate is purely over the types of over-ear or circumaural headphones, which are closed-back and open-back headphones.
As you can probably guess by the name, these two categories are based on the difference in their form factor.
Open-back headphones are designed such that the outer shell of the ear-cups is perforated in some way.
These perforations are typically horizontal cutouts, but you can find several variations.
The purpose is to have a lot of openings on the back surface. What effect does that have on your music? We�ll discuss that later, but right now, let�s talk about the difference in the form factor of these two types.
On the other hand, closed-back headphones, as the name suggests, have a solid construction of ear-cups from edge to edge with no openings.
While these terminologies are clear regarding physical design, they don�t indicate what effect do these design changes have on the listening experience, so let�s dive into that.
The biggest upside of closed-back headphones and the main reason why you�d prefer them over the open-back design is that this option gives you excellent noise isolation. Active noise-canceling isn�t being discussed here; instead, we�re talking about noise isolation which occurs due to the ear-cups entirely covering the ears and ensuring most of the ambient noise stays out.
Closed-back headphones not only use their closed-back over-the-head design for noise isolation, but they also rely on an insulated plastic shell to cover your ears. This provides 10 dB of noise reduction. This noise isolation, combined with music, does a good job of dampening or fully eliminating the ambient noise.
However, that is also the biggest advantage of using closed-back headphones. They provide excellent noise isolation and enable you to enjoy the music in your ears, so when you use them to listen to music in a surrounding where it is important for you to listen to ambient sound such as when jogging, most of the ambient sound will be dampened out or removed entirely.