Open-back headphones give consistent bass response across listeners because fit does not affect it.

Evidence

In open-back designs the space behind the transducer is fully exposed or in semi-open designs partially exposed to the outside. Sound can freely pass inside to the outside and vice versa. This makes open-back designs more suited for solitary listening in quiet spaces. Open-back designs can produce low bass but typically less bass than closed-back designs. Because the fit and seal have little impact on the bass performance, the frequency response tends to very consistent across listening sessions and among different listeners. This makes them excellent choices for psychoacoustic experiments. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1697

Categorization

• QUESTION: Best response consistency across listeners is precisely what psychoacoustic experiments need; worth chasing the fit-seal literature further given the reading purpose.