Gear & technology
Open-back
Also called open headphones, open design
Open-back headphones have earcups that let sound pass through the outside, usually through a grille. They leak sound both ways, so they are for quiet rooms, and they are widely preferred for a spacious, natural presentation.
With no sealed chamber behind the driver, the air inside the cup is not compressed, and the rear wave of the driver escapes instead of reflecting back. Owners describe the result as open, airy and less "in the head" than a Closed-back design, which is why open headphones dominate home listening and mixing.
The trade-offs are practical: everyone in the room hears your music, and you hear the room. Sub-bass is often a little lighter too, since there is no seal to pressurize. The Sennheiser HD 600 and HiFiMAN Sundara are classic open designs.
Whether the open design itself makes the Soundstage larger, or whether it is the tuning that tends to come with it, is debated among listeners.