A type of speaker enclosure used for subwoofers and bass drivers which uses a small, sealed enclosure with two bass drivers facing each other (one inside the box facing out and the other outside the box facing in at its counterpart) and wired out of phase. The primary advantage of this type of configuration is that the enclosure is small – about half the size of a sealed enclosure for the same output. The enclosure must be sealed and the two drivers must be sealed together. Isobaric enclosures leave one driver essentially hanging out in the open air making it a somewhat challenging configuration to achieve due to aesthetics and the need to protect the driver outside the box. This type of configuration is sometimes found in car audio but is rare in home theater and other home audio systems.