They may have an open-back design, like an electric guitar combo amp; most bass combo amps and speaker cabs are closed-back (often with bass reflex ports or vents).
They may have an open-back design, like an electric guitar combo amp. The use of an open back cabinet in small practice amps makes these models different from most bass combo amps and speaker cabs, which are closed-back (often with bass reflex ports or vents).