Open-back headphones do not have an insulating, hard cover on the outside of the speaker.
Open-back headphones do not have an insulating, hard cover on the outside of the speaker. Without that cover, sound tends to be clearer because it doesn’t bounce around an enclosed space (a phenomenon known as resonance). The downside is that open-back headphones don’t block out ambient noise as well. They also let the sound out. For these reasons, open-back headphones are best for quiet studios.